2003 Chevy Trailblazer Transmission

The 2003 Chevy Trailblazer was built on the same platform as the Colorado and GMC Canyon twins.  They were both rear wheel drive and used the same drivetrain components (for the most part).  Trailblazers used the 4L60e across the board regardless of which engine was in front of it.  But, these particular versions of the 4L60E use a different bell housing than the LS engines.  This means you need to be really careful when you’re looking for a replacement transmission, because they’re not easily swapped for one another.

The later 4L60E transmissions use a two piece bell housing, which means that you can swap the bell housings out.  The Trailblazer came from the factory with Dex III transmission fluid.  General Motors suggests that you replace it with Dex VI.  The “drain and refill” transmission fluid capacity is 5.0L.

2003 Trailblazer Transmission


Common Trailblazer Transmission Problems

By 2003 the 4L60e had a decade of refinement to it, which made the transmission one of the most reliable things on the vehicle.  In fact, there were so many issues with the L6 engines that were put in these vehicles that the engine would almost always give out before the transmission.  I don’t really have any statistics to back that one up, but I have seen plenty of real life examples of that exact scenario.  If you’re one of the few people lucky enough to have a v8 version of the Trailblazer you’re

If you’re reading this at the time it was written, the 2003 Chevy trailblazer is 15 years old. That means that there has been a lot of time for parts to degrade.  Fifteen years is a lot of time for a wiring to go bad, harnesses to come loose, or not have any maintenance done.

Here’s more on 4l60e problems.

Bad Fluid

When you’re looking for a transmission problem in an older vehicle a good place to start is to take a look at the transmission fluid.  Does it smell burnt? What color is it?  It can tell you a lot about the condition of the transmission.

If your Trailblazer has it’s original transmission it may have never been changed at all.  Transmission fluid is one of the most neglected pieces of automotive maintenance.


Limp Mode

When it comes to entering limp mode, these transmissions are notoriously fickle. The transmission enters limp mode because their is some sort of electronic sensor that is giving it a signal that is out of it’s normal operating range, usually one of the shift solenoids.

Here’s much more on limp mode.


Swap Compatibility

If you choose to replace the transmission yourself you need to be really sure that you are getting another 4L60E that is compatible with the one that you are pulling from your Trailblazer.  Certainly a 4L60E from the 90’s is not going to match up.

You’ll need to find a transmission from an L6 GMC Envoy or Trailblazer, if that is the engine you have.  If you have a V8, your options are wide open.  Just make sure that you are checking that they are compatible.  Here are a few good resources for that:




How much should a rebuild cost?

The 4L60e has been around for very long time, and is one of the most mass-produce transmissions ever made. That’s good news for you, because that means that there’s plenty of replacement parts available, and they’re relatively cheap.

Also, another thing that you have going for you is that The 03′ Trailblazer is rear wheel drive, which means that pulling the transmission is relatively easy to do.  This will keep your labor cost down quite a bit compared to working on a front wheel drive vehicle.

If you are looking to take an 03′ Trailblazer in to have the transmission rebuilt and replaced, $2000 is a pretty good price.



While the 4L60E that comes in the Chevy Trailblazer ( and GMC Envoy) is incredibly durable, they can go bad.  If they do go bad it’s important to replace it with a similar transmission.  There are many compatibility issues.  If you do your due diligence, you will have your 03′ Trailblazer back on the road in no time.

Posted in 4L60E

What Color is Transmission Fluid

What’s in a color?  The answer is a ton of information when it comes to transmission fluid color.  It is one of the best ways to tell the overall health of your transmission.

What does healthy transmission fluid look like?  The short answer is a nice amber color.  And, that is assuming that you even have a manufacturer that starts with amber transmission fluid. There are some vehicles that use other colors, but for the most part they all use a transmission fluid that starts with some sort of bright red clear color.

Transmission Color Chart

All bets are off once the transmission fluid leaves the bottle.  As soon as it enters the case it gets to work doing many jobs that are required of it.  The fluid will begin to darken in color right away. This changing of the color doesn’t necessarily mean that there’s anything wrong.

There is simply an amazing amount that you can learn about a vehicle by looking at the transmission fluid.  Just like motor oil, automatic transmission fluid gets darker with age.  This is itself does not necessarily indicate a problem.    Heat can cause ATF to darken over time.


Light Amber or Red Colored Fluid

Red Transmission Fluid Graphic

The red color that you see in transmission fluid is from a dye added to it.  Without it there would be almost no color to the fluid at all!  Don’t be deceived if your fluid looks great.  The color of the fluid is not an indication of transmission wear, or the last time that it was serviced.



Maroon Transmission Fluid

If yo check your transmission fluid and it appears as a nice maroon color, that is an indication of fluid that has been in the case for quite a few miles.  Heat causes the dye in the fluid to change color and get darker.  Fluid that is this color is usually just fine.  In fact, some ATF even comes that dark straight out of the bottle.



Brown Transmission Fluid Color

If you are having difficulty distinguishing from the color of your transmission fluid and motor oil, than you officially have dirty transmission fluid.  Dirty does not mean dangerous though, and is not cause for alarm by itself.  If the only  thing that appears to be wrong is that the transmission itself is in need of a proper a servicing.

You’ll see the situation a lot where someone is looking to but a car and they are really put off by the dirty fluid.  It is not an indication that anything is wrong with the car.  But, brown fluid should serve as a warning that the maintenance schedule has not been followed.

Extremely Light Pink Fluid

Pink Transmission Fluid Color

This color is an indication that antifreeze or water has corrupted the transmission.  Of all of the colors mentioned, this is the one that would give me the most concern.  Water is almost impossible to get out of the transmission.  It usually gets in there through a failing radiator.  It can also get in there if you drive through floodwater.

If you have fluid that is this color get your transmission looked at as soon as you possibly can.  Water is actively destroying your transmission.  Anti-Freeze is especially corrosive.

Water contaminated transmission fluid can also have a foamy look to it.  This will occur when the radiator or damaged line is allowing bother air and water in.


Black Transmission Fluid

Black Transmission Fluid Color

While amber, brown, and black are  usually harmless, that is not the case with black transmission fluid.  The reason that the fluid has gotten to be black is because of issues in the transmission.

To the untrained eye, brown and black transmission fluid have similar colors.  If you are unsure give it a sniff.  Black transmission fluid smells.  It smells bad because something has burned in order to get that smell.  It is usually caused by worn and slipping clutches, torque converter problems, or other transmission failure.  It is an indication of a serious problem and the transmission is going to require servicing.

Silver Tint or Silver Shavings

If you run into any of the colors above and find silver shavings in it, you have a major problem with the transmission.  I know most mechanically inclined people are thinking “well of course there’s a problem”, but you never know who is going to be looking to a page like this for help.

This indicates metal on metal friction.  Parts are actively grinding against each other.  Failure is imminent.  Get your transmission serviced as soon as possible.


What happens is you overfill the transmission fluid?

The transmission fluid may foam and ironically become starved for lubricant.  More on that here:  http://www.doityourself.com/stry/can-too-much-transmission-fluid-hurt-a-vehicle


What does Automatic Transmission Fluid do?

ATF moves the heat generated by the engine to the radiator. It lubricates the transmission, and it moves the power through the torque converter. That’s a lot for one fluid to do.

Transmission fluid is a type of hydraulic oil.  It is highly flammable.  A motor uses oil for lubrication, water for cooling, and a crank and pistons to transfer energy to the rest of the vehicle.  Transmission fluid combines all three of these jobs into one fluid.  It needs changing way less often and is often one of the most neglected parts of the vehicle.


Looking at the coloration of the transmission fluid is a great way to determine what is going on inside your transmission..  Remember, a color other than red or amber does not necessarily indicate a problem.  Regardless of the color of the fluid, if the it gives off an odor and smells burnt, get the transmission looked at.



Posted in tech

Limp Mode Causes and Solutions

Any automatic transmission made within the last 15 or 20 years is going to be a computer controlled.  And, just like a modern engine, the computer now knows when there’s something wrong with the transmission.  If the computer thinks that there’s some sort of critical problem is going to destroy the transmission, it will put the transmission in something called limp mode.  Limp mode can also be referred to as fail safe mode.

What is Limp Mode?

Limp mode is a condition where the computer will make the transmission operate in a manner that will save it from its own destruction.  Limp mode’s job is to minimize the potential harm from a major mechanical failure.  As the name itself implies, it is designed to get you and your vehicle safely in for a repair without leaving you stranded on the side of the road.

What Causes a Vehicle to go into Limp Mode

The computer generally does this by reducing the number of gears the transmission can use.  Although which gears are eliminated generally changes depending on which transmission make and model it is.   It’s generally a rule that the overdrive gear will always be deactivated by this limp mode condition.  Typically, the torque converter will stop locking as well under limp mode conditions.

An automatic transmission has a range of signals readings from the sensors that the computer sees as normal.  When one of these sensors sends a signal outside of the normal operating parameters limp mode is triggered.  The transmission will often shift rougher, and the torque converter lock will stop engaging.  Most people realize this happened when they get on the highway and their vehicle screams down it at a high RPM.  Besides the limited and firm shifts coming from the transmission, many vehicles have a noticeable lack of power coming from the engine as the computer does everything that it can to save the transmission.

Common Causes

There are several different conditions that can cause limp mode. The common theme of the issues listed below are a faulty reading from a sensor that is critical to the operation of the vehicle.  Once you understand that, than the only question left to ask is it a false reading or is there something really wrong?

  • Computer Problems–  A problem with the vehicles ECM can cause limp mode, although this is definitely not where you should start looking, but
  • Damaged Electrical Connection–  Over the life of a vehicle the wiring harness that connects the transmission to the ECM can become damaged.  This can alter the signal that the computer receives, triggering limp mode.  This is much more likely than a computer problem.
  • Loose Connection–  Older vehicles have had over twenty years to get a loose connection on one of it’s wiring harness plugs.  All wiring harnesses utilize plastic keepers to secure them to the sensors.  Plastic melts and breaks just like everything else.  Has your vehicle been in the shop in the last few months?  Maybe the mechanic damaged a connection or didn’t quite get a harness snapped in all of the way.  You would be shocked just how much this can and does occur.
  • Water Damage–  The thing about modern vehicles is that they are virtually bulletproof compared to the old non computer controlled predecessors.  But, their Achilles heal is the complex wiring that they use to operate.  It can be confusing to deal with.  If you’ve gotten the harness wet or suspect your vehicle has been in a flood, this very well could be causing your limp mode situation.
  • Faulty Sensor–  Your vehicle relies on many sensors.  These include the MAP sensor, throttle position, crank position, and vehicle speed.

What Limp Mode Does to Protect Your Vehicle

If your vehicles ECM receives signal that there may be a potentially catastrophic issue, it’ll trigger the limp mode and trigger your check engine light.  It than switches all of the vehicles timing and shift tables over to a less aggressive (and therefore less damaging) performance table.  Think about it like starting your computer in safe mode.

Limp Mode Causes and Solutions

In a transmission the computer will increase the pressure in the lines in order to protect the clutches.  This makes shifts way more rough (if your vehicles limp mode gives you more than one gear)  Although it seems counterintuitive, a hard shifting transmission is better on the clutches and bands because it allows for less slipping.


All vehicles built after 1996 have OBD2 built into them.  Head to your nearest AutoZone and have it tested.  Make sure that you head the limp mode warning and actually take the vehicle in for repair and don’t drive it like that for long.  There is a good chance that you could be causing more damage to the vehicle every second that you continue to drive it.  Hopefully you won’t end up finding out that you are looking at a major repair.  Good luck!

Posted in tech

Signs of Torque Converter Problems

The torque converter is responsible for converting the energy generated by the engine at the flywheel and transferring it to an automatic transmission.  It functions in the same place in the driveline as a clutch would, creating a bridge between the engine and the transmission.  When they go bad, they have the potential to leave you stranded.   Understanding them certainly can keep you from being stranded on the side of the road.   So let’s go over common torque converter problems.

The biggest difference between a torque converter and a clutch is how they transfer the energy between the flywheel (what a clutch connects to) or the flex plate (what a automatic transmission connects to).  The clutch will slip using physical friction between the clutch disk and flywheel.  The torque converters hydraulic connection builds pressure as rpm increases.  This is worth noting because it’s important to understand how something works to properly diagnose and fix it.  Here is more on exactly how a torque converter works if you are so inclined:


Causes of Torque Converter Problems

There are many different things that can cause torque converter problems.

  • Low or Dirty fluid–  Transmission fluid is the lifeblood of the transmission and the torque converter bolted to it.  If there isn’t enough it can’t do its job.  This  will in turn cause the transmission to overheat.  This is one of the most common causes of torque converter problems.  If the transmission fluid is dirty and old it won’t be able to do its job as a hydraulic fluid as well.  This can lead to a feeling of extra slipping and chattering at speed.  Make sure you take a look at the fluid before you do anything with your transmission.  If you don’t know or can’t remember the last time it was changed or serviced this would be the place to start.
  • Worn Clutches–  The clutch that locks the transmission to the engine at highway speed can wear out just like a normal manual transmission clutch.
  • Bad Seals–  This is one of the most common issues that causes a torque converter to go bad.  It’s usually pretty detectable, as there will be a pool of fluid beneath the bellhousing.
  • Loose Torque Converter Bolts–  This will create the same symptoms as the bad seals in that the converter is going to puke a bunch of ATF all over your garage floor, but you should also be feeling quite the vibration at speed.  If you suspect this could be what is going on with your transmission, just know that if those bolts come all the way out the least that is going to happen is that it disengages from the input shaft.  Most likely it’s going to really do some real damage to the crank and input shaft.

Faulty Torque Converter Diagnosis

Above we laid out the issues that cause a torque converter to go bad. Here we are going to discuss what it actually feels like in your vehicle.  Before diagnosing any transmission issue, you’ll want to drive to let the engine warm up to its normal operating temperature.  This will ensure that the transmission is shifting as it would nearly all the time that it normally operates.

After you’ve let the transmission warm up turn the radio off and roll the windows up.  You’re going to want to pay maximum attention to what’s going on with both the engine and transmission.  Pay particular attention to any shuddering and vibration as you accelerate.  Shuddering and vibration are in no way a guarantee that something is wrong with the torque converter.  I’ve outlined a few examples of other things that could be wrong if there is a vibration below.

A common issue that happens with front wheel drive cars is that the axle shafts (or cv shafts) go bad.  This can create a similar vibration, but it will get worse or only exist when you go around corners.  Below are signs that will tell you if the torque converter is damaged or going out:

  • Slipping Transmission at low speed-  The torque converter “stall speed” is the speed that the engine needs to be turning before the torque converter will begin engaging the transmission.  When a torque converter is malfunctioning it can cause this stall speed to change and feel like the transmission is slipping.  If you suspect this is happening with your car, has your fuel mileage changed?  This iso fen a sign that the transmission isn’t operating efficiently.
  • Slipping at highway speed–  Nearly all modern automatic transmissions have what is called a locking converter.  This type of  torque converter has been the standard since the mid eighties, and is universally used today.  What it does is have  clutches in it that let the transmission make a physical connection with the engine.  This eliminates all operating inefficiency when it is at high speed (usually after about 45 miles an hour).  This increases the fuel mileage achieved and brings an automatic transmissions efficiency more in line with a standard transmission.
  • Chattering or vibration–  If you feel a vibration going down the road it could very well be the torque converter.  The fluid level may not be where it needs to be.  Have you ever had an uneven load in the washer?  It spins around and the washer sounds like it is beating itself to death.  The torque converter is the same way when it can’t spin the right amount of fluid through itself.  It is way less likely, but the bolts that hold the torque converter to the flex plate can come loose and cause a vibration at speed.

Repair the Converter ASAP

A torque converter has the potential to keep on going for months after it first starts to go out.  But, when it does, it’ll blow out and toast the transmission.  It’ll rain debris and metal destroying it almost instantly.  Don’t put it off.  If you aren’t sure, take it to a garage and have it looked after.  Putting it off is going to cost you big money and is dangerous.


Cost to Replace a Torque Converter


If you are positive that you have a bad torque converter, than replacing it is a must.  Torque converter replacement cost is going to depend a lot on what type of vehicle you are driving.  In general, a front wheel drive vehicle is going to be more expensive from a labor point of view and could cost anywhere between $300-$1000 depending on the vehicle.

Torque Converter Problems

If you are going to attempt to replace the problematic torque converter yourself, than you certainly are going to be saving yourself tons of money.  If the vehicle that you are attempting to fix is front wheel drive, than it’ll be more difficult to do than a rear wheel drive.  This is due to the transmission location.  99% of the battle is just getting to the converter.  After that it’s a pretty simple fix.  Just a few bolts, slide the converter off of the input shaft, and tighten it back down.  If you’ve never done this before try and start at the beginning of the weekend to give yourself plenty of time and you can save yourself a ton of money.


Posted in tech

4L60E Transmission Problems

The 4L60E transmission is the direct descendent of the 700R4, and as such already had over a decade of refinement put into it before it ever even made it into production.  This means that even the early ones were pretty good from day one of their production life.  While there have been many case changes and internal changes throughout the years.  Ok, time to stop rambling.  Lets get into 4L60E problems and how to troubleshoot them.


4L60E Troubleshooting

It is important to understand a few things about how an automatic transmission works.   There is fluid that goes through the 4L60E that has three jobs:

  1. Lubrication
  2. Cooling
  3. Energy movement

That’s a lot for one fluid to handle.  Motor oil is only responsible for lubrication and cooling and is changed way more than transmission fluid.  Tranny fluid is one of the most neglected items of vehicle maintenance.  So before you go crazy thinking about what part may be giving you a difficult time, try making sure that the fluid isn’t the culprit.  This is especially true if you’ve recently towed something or been racing.  So if your 4L60E is acting funny after you’ve done one of these things, why don’t you just go ahead and change the fluid just to be safe.

Here is a good write up on low transmission fluid signs.

This is a good writeup on taking care of a tow vehicle


If the 4L60E is not shifting through the gears like it should be and the service engine soon light comes on than you’ve probably entered limp mode, limp mode is gear 2, 3, and reverse.  It will have no overdrive and no first.  The first thing that I would check is whether or not is is getting power from the ECM, and whether it is sending a signal back to it.  It’s way more likely that this has happened than you have a major issue.

If it isn’t an electronic issue causing limp mode, it’ll be a mechanical one.

If you find that your vehicle is vibrating at highway speed, this is often caused by a loose torque converter.  You’ll probably find that you’ll get this feeling at particular rpm ranges.   For instance, maybe you’ll feel a shutter from 1800-2000 rpm, but the engine will be fine above or below this range.  That is either the torque converter or harmonic balancer.  Make sure you aren’t confusing the shutter of a poor running engine with the vibration of a transmission with a loose converter.


Common 4L60E Problems

4L60E goes into neutral when shifting into third gear

This is one of the most common problems with the 4L60E.  It is pretty easy to diagnose.  The vehicle will shift from 1’st gear to second gear with absolutely no issue whatsoever, but than it acts like it has shifted to neutral.  The engine is usually under a pretty heavy load at the time, so it’ll tend to redline before you realize what happened.  Good thing these engines have rev limiters!  It can be a pretty scary feeling.

This is caused by a burned out 3-4 clutch pack.  And, the 3-4 clutch pack is done in by the 3-4 piston.  There is a giant rubber O-ring around the piston that will shrink due to heat and age.   Nearly everyone is going to have to take it on in for a rebuild.   Replacing the clutches in an automatic transmission is not a job that is easily done whatsoever.  There is a lot that can get messed up in the 4L60E

4L60E has forward gears, but no reverse

This is also a pretty common issue with the 4L60E.  More than likely the reverse input snap ring has sheared or snapped off. It can also be caused by the sun shell breaking.  The most common problem is probably going to be the low reverse clutch pack.  The booster valve could also be an issue.

Below is a pretty good video on common causes of 4L60E reverse going out.


Harsh shifting

Many people will bring their vehicle in and complain that the transmission is shifting really hard between first and second gear.  This is another really common problem with the 4L60E.  It would probably be a good idea to check the throttle position sensor and see if it is within it’s normal operating parameters.

Here is a good article on TPS issues.

Below is a good video on TPS diagnosis.


If you’ve had problems with the 4L60E after a rebuild, check this article from LS1tech.com.

Whatever is going on with your transmission, I hope that you are successful in fixing it, and you don’t end up losing an arm and a leg on repairing your 4L60E.  Good Luck!

Posted in 4L60E

TH350 vs. TH400

One of the largest questions amongst Chevy guys is TH350 vs. TH400.  Which one is better.  Even though they have been out of production for decades, there is still a strong demand for them.  Their simplicity and durability make them attractive to people in the LS swap community.  They are certainly are both great transmissions.  They share the same bolt housing patterns, and often came behind the same engine types.  Whereas the TH350 would be found behind a lower performance small-block 350 Chevelle,  the TH400 would be the transmission that came with the 454 SS.  The TH400 also found itself in many heavy duty trucks and vans.


TH350 Transmission TH400
First-  2.52

Second- 1.52

Third- 1.00


First-  2.48

Second- 1.48

Third- 1.00


Input Shaft Splines



Output Shaft Splines


21 5/8”

Length from Bellhousing to Tailshaft




Differences between the TH400 and TH350

The TH350 is certainly smaller than the TH400 and can usually fit into nearly any rear wheel drive  Chevrolet passenger car with no problem.  Tunnel modification can come into play on some of the smaller cars.  The TH350 uses a mechanical kick down switch, whereas the TH400 uses an electric one.  The electric kick down is much easier to set up, espescially if you are doing an LS Swap,

They do both have an aluminum case, and three forward gears.  Although the gear ratios are nominally different.  Neither transmission has any sort of computer control to it, nor did they use locking converters.

A lot of people claim that he TH350 has less drivetrain loss than the TH400, which means that all things being equal, the TH350 is going to get more power to the rear wheels from an engine with equal power.  This is due to more rotating weight existing in the larger TH400 case.  Here is a writeup on ET loss from TH350 to TH400.

They also don’t weight the same amount.  The Turbo 350 weights 150pounds while a Turbo 400 weighs almost 170.

Which one is right for you?

If you are going to buy a stock transmission and know it’ll fit in your vehicle, without a doubt the TH400 is the way to go.  It’s super durable and will provide a long life of useful service with no modification from stock, even in higher horsepower situations.

If you are buying an aftermarket transmission from someone like TCI or Monster transmission, I’d say go with the TH350.  These folks have had decades to get all the flaws and weakness out of it.  You’ll have less mass in the drivetrain and a lighter transmission.

Thank you for reading!

Posted in tech

C4 Specs + Identification



The C4 is a transmission that was produced by the Ford Motor Company starting in 1964.  When first released it was known as the “3 Speed Cruise-O-Matic”  Like GM and the switch from Powerglide to TH350, Ford replaced the iron case of the “Ford-O-Matic” that it replaced.  It was engineered to work with rear-wheel drive vehicles.

The transmission stayed relatively the same for its first 5 years of production.  In 1970 the engineers at Ford gave it its first design changes.  These changes gave the C4 upgraded internals capable of handling more power and increased its durability.

The C4 was used in light duty vehicles such as the Mustang, Torino, and Falcon.  It also was used in the F150 until production ceased.  It still is a pretty popular transmission with bracket racers due to its 110 pound weight.  Unlike most early transmissions, where the case is fused with the bellhousing, the C4’s is removable.  this allows it to be custom fit to vehicles it was never intended on running in.  Regardless of model year, the C4 can have a dipstick that goes directly into the pan or the case.  Usually car versions had the dipstick in the case.

In 1982 the C4 was upgraded to the C5.  Like in 1970, it was upgraded to handle more power and increase reliability.  It also got a locking converter to help Ford meet ever tightening fuel mileage requirements.  This transmission lasted for only 4 years.


C4 Specs

Manufacturer:  Ford Motor Company
Production:  1964-1982
Type:  3 Speed Automatic
Gear Ratios:

  • First- 2.46:1
  • Second- 1.46:1
  • Third- 1:1
  • Reverse- 2.18:1
Input Shaft:

  • 1969 and older:  24 spline
  • 1970:  26 spline
  • 1971 and up
Torque Converter Lock:  No
Overdrive:  NO
Case Length:Different applications had different lengths due to different tail shafts/transfer cases.
Outer Case Material:  Aluminum
Controlled by Computer: No
Weight:  Roughly 110 lb. without the converter or fluid.


C4 Transmission Identification

There is not much to figuring out whether or not you are looking at a C4 transmission.  The real trick is identifying which C4 you are looking at.  Lets get straight to it.  The C4 was never put behind any engine that had a displacement over 400 cubic inches. So, unless you are looking at any big block other than the 400, you can rule out the C4.

The speedometer cable is attached to the driver’s side tail shaft, if you are looking under the car, that is a good place to start.  The tail shaft or transfer case bolt to the C4 with six bolts.

The most effective way to identify which three speed Ford automatic that you are looking at is to count the number of bolts used to secure the transmission pan.  They each use a different number, so there really is no confusion.   There are 11 bolts on the C4.  Pan shape is more uniform than GM automatic transmissions, but they each do have a different shape.

C4 Identification

As stated earlier, the 1960’s version of the transmission had a vent tube on the passenger side.  It was eliminated for the 1970 model year and never returned.  So if you see that tube, you can fairly assume that you have identified an early model.

In the 1970 and later version it has something called a “jiggle pin”.  It stays on top of the housing by the tail shaft and vents the case.  It is just a basic valve that pops open when the case gets enough pressure.  If you happen to be looking at a transmission without a tail shaft/transfer case you can identify it as a C4 4×4 transmission by the tube coming from where the jiggle pin normally would be.  Either way, if you see the jiggle pin you know you have found a 1970+ model.

1973+ models have a push in modulator, whereas all the earlier ones screwed in.  The modulator is located on the back of the case above the pan.

You can tell whether you have the weaker car line version of the C4 by looking at the bolts that fasten the bellhousing to the case.  If the bolts hold the pump and the housing than it probably came from a car.  The car versions also used a shallower pan until the late 70’s

There are so many different versions of the C4.  There are over ten different bell housings depending on which one you are looking at you need to make sure that it is compatible with the engine that you would like to drop in.  They are removable though, so don’t sweat it too much, but it’ll give you a great idea where the transmission came from.  Here is a pretty good guide to figuring out which bellhousing is currently on your C4.


The C4 transmission is still a great transmission to use for your hot rod, bracket racer.  Finding them at swap meets isn’t very hard.  Keep your eyes peeled and you’ll find one on craigslist for under $200.  As long as you feel like you don’t need overdrive you can’t go wrong with it.


Posted in Ford

Common LS Swap Issues

If you are considering swapping out your motor for an LS motor, there is a lot to consider.  It is totally doable, and absolutely worth it.  The performance and drive-ability improvements that these engines add to an older model vehicle are amazing.

The best way to approach the swap is to think of it like a jigsaw puzzle.  There are a few key pieces that need to fit together to make a success of your effort.  These include engine mounts, crossmember, headers, and accessories.  They all need to work and fit together.  You’ll have a much better time swapping out your engine if you address these areas of concern before you buy any parts.  There are many companies out there who make parts that can make swapping an LS motor into your car a breeze, but they are going to cost more than generic parts and fabrication.

Alternatively (and just as importantly), there’s almost certainly a post or forum out there on a forum where someone has covered every aspect of the swap in great detail.  LS1tech.com is a great place to start.  Use this information to your advantage.  If you can find a forum entry where someone has laid out every single aspect of the swap, than you are ahead of the game.  Try and replicate what they have done.  Instead of figuring out the geometry and mechanics of the swap, you can just start doing it.  You’ll save so much time.

Hours of prep will save you weeks of delay.  It will also save you a ton of money on parts that don’t match.  With that in mind lets get into what you absolutely should know before buying any single part.  There is almost a universal truth when it comes to the LS swap, and that is that there are inexpensive parts, and they’ll work.  But, those parts are almost never vehicle specific, and vehicle specific parts cut down on the frustration and time it takes to do this swap.

Choosing the Engine for your LS Swap

There are many variations of the LS engine, and the cost for them varies wildly.  There are truck engines, and exotic supercharged aluminum versions used in the Corvette.

  • Gen III is a bit easier to run due to the lack of variable valve timing.  It’s also quite a bit cheaper than the Gen IV small-block.
  • Given that the mileage and model year is the same, truck engines are significantly less expensive than the car engine.
  • The truck intake manifold is not as aesthetically pleasing, it is also taller.  So, if clearance is an issue keep that in mind.
  • The accessories on the truck engines are further from the block than the Camaro.  And, in turn, the Corvette has closer accessories than the Camaro.
  • Some engines use drive by wire (electronic) and some use drive by cable (throttle cable).  If you go with a drive by wire you’ll be able to easily set up cruise control, but that also means modifying the throttle pedal in order to fit the vehicle.  This forum has quite a few good examples of what this would take.  Be prepared to weld.

I can’t stress enough how important that it is to try and get an engine as complete as possible.  When getting one from the salvage yard, make sure that you are getting the transmission, harness, accessories, intake, etc…  If they all come from the same pull than there is no question of whether or not they’ll work together.



The LS engines will bolt with any of the non computer controlled “old school” transmissions.  They certainly work best with the transmissions that they were designed to run, but they’ll do just fine with say a TH350 or TH400.  There are a few things to consider when deciding what to do about the transmission.

We have a whole post on that LS Swap Transmissions if you would like to learn more about it.

Crossmember and Motor Mounts

This is an incredibly crucial aspect to the swap.  You can buy some inexpensive universal LS swap motor mounts on eBay or Amazon.  They may or may not work with your engine bay.  One thing that people often overlook when it comes to the swap is pinion angle.  If the pinion angle is off because the motor mounts are different (even if you leave the factory crossmember) the driveline is going to vibrate the car at speed, which makes the quality of ride not nearly as pleasing.

Fuel System

Most people who do this swap are swapping it into a vehicle that came from the factory with a carburetor.  LS engines want around 100 pounds of fuel pressure to properly atomize the fuel and deliver it to the cylinder.  The factory fuel lines are just not going to be able to handle that kind of pressure.   An electric fuel pump is a necessity, even if you are using a carb.   There’s inline and in tank fuel options from vendors such as Tanks Inc.  This is an area that can really blow out the budget.  You can spend about $100 to get the basic setup, or full blown EFI tank with pump and lines is going to be $700.

Headers and Exhaust Manifolds

The stock exhaust manifolds that came with the engine itself are usually fine for most applications.  You’ll find that the LS1 (and car motors in general) manifolds stay closer to the block than the truck engine’s manifolds, which makes them fit in more applications.  If you are swapping in a truck engine than it may be necessary to use a Camaro/Vette manifold on the steering box side.  Headers can be tricky.  They really should be considered with the motor mounts.


There are two aspects to the wiring that must be addressed.  The first one is the wiring harness itself.  There are plenty of youtube videos and online tutorials that’ll help get the wiring harness straightened out.  The best source for this is lt1swap.com.  Here is a link to the best page to start.


If the prospect of removing all of those pins and wiring seems a little to much (I always farm this part out), I recommend sending off for a rework.  There are plenty of people on eBay who provide this service for $100 or so. Here is a video that shows what is involved. This guy has some great videos for a swapper to watch.


The second thing is the ECM.  It has to be reprogrammed.  There are security measures associated with it where it can’t just be plugged in and run.  The anti-theft system must be deleted.

Unlike the wiring, which you can do yourself, the ECM is going to need to be shipped out to be reprogrammed.  Odds are you can find someone in your area who will do it for you on the cheap.  Otherwise you can check eBay.  People are always auctioning off rewiring/reprogramming services on there.  The going rate is around $60.  This will get the ECM ready to run a stock motor with no modifications.  The tuners can remove the active torque management as well, if it’s a drive by wire setup.

If the engine in question is getting a camshaft that “requires tuning” than you’re going to have to send off for a special programing to make it run properly with it.    Alternatively if you live in a major metropolitan area there should be a local speed shop to handle it for you.  As far as the mail in tunes go, black bear is the best there is.  Check them out


Cooling System

The LS engine runs pretty cool, so most factory radiators can handle the heat generated by it.  Now, there is one thing that must be addressed.  The steam vent tube.  Some people block it off or don’t know what to do with it.  It needs to be run to the radiator, or back to a radiator hose.  Those are your two options.

Posted in LS Swap

Best 700R4 Rebuild Kit

The 700R4 transmission has been around of a very long time.  In fact, it hasn’t been in production in over 20 years.  It remains popular due to its reliability and adaptability.  If you are thinking of attempting to rebuild a transmission for the first time, be warned.  Rebuilding one can be more challenging than rebuilding an engine for a first timer.  In fact, you should check out this YouTube video.  It’ll help you determine whether or not it is up to your skill set to attempt.


700R4 Rebuild Manuals



ATSG 700R4 Rebuild Manual700R4 Rebuild Guide

Whether you have the experience rebuilding transmissions or not, it’s really important to have a rebuild manual.  It will tell you things about the intricacies of the transmission that you are working on.  There may be a different part, or part location in a particular year.  You won’t usually find that in a YouTube video.  That’s not to insult youtube, which is an invaluable tool when it comes to rebuilding any car part you’ve never worked on before.

As far as standard rebuild manuals go, you can’t really go wrong with the ATSG Manual on any transmission.  Their 700r4 rebuild manual has top notch diagrams and information to help you make sure that you are doing the job right.

Click Here to Check Price on Amazon


SA Design’s Builders and Swapper’s Guide700R4 Swappers Manual

This is a fantastic rebuild guide for someone looking for a high performance transmission build.  The book has more of an informal tone than the latter rebuild manual.  It is written in a more informal tone.  It also comes in a Kindle Edition, which is nice if you want to read it now or keep it on a mobile device.  It can be hard to read a Kindle while wrenching on a vehicle though.

Click here to Check Price on Amazon

Standard Rebuild Kits


 Alto PowerPackBest 700R4 Rebuild Kit

This basic kit comes complete with:

  • High Energy Carbon Band
  • A New Filter
  • Trans Valve Body Separator Plate
  • Corvette Servo

Click Here to Check Price on Amazon


Performance Rebuild Kits

Most folks are going to want to make their unit stronger if they are going to go through all of the trouble to rebuild their 700R4 transmission, and there are tons of kits out there to help you achieve that goal.

B&M 70233 Transkit 700R4 Performance Rebuild Kit

B&M has been making high quality transmissions, shifters, fluids, and much more for decades.  This high performance kit is great for anyone looking to really get some power to the pavement.

  • Made for the 1987-1993 700R4 in particular
  • The have the same components that B & M uses to build their bulletproof transmissions
  • High performance materials
  • Complete gasket set
  • Drain Plug
  • High performance valves and springs
  • 1 year warranty


Click Here to Check Price on Amazon


700R4 rebuild kit with torque converter

There are a lot of variables that come with choosing the proper torque converter for your application.  If you are rebuilding a stock 700r4 transmission, than you should be fine just re-ordering a stock converter, or going with one that has the same stall speed as the car had from the factory.  If that is not the case, than you are going to need be very careful about picking the right converter.  In a modern LS type engine, even when they make good power the stall doesn’t have to be extreme because the heads make more power.  This allows for a less aggressive cam profile, which allows the engine to retain decent bottom end power.  Try using this guide to picking out a torque converter from Super Chevy.



The best 700R4 rebuild kit is going to largely depend on what budget you have, and what kind of power you plan on putting to the pavement.

Posted in 700r4 Parts

700R4 Transmission Troubleshooting

It’s been over 20 years since the 700R4 made it into a production vehicle.  While they have been fairly reliable over the years, we have written this guide specifically to help with troubleshooting your 700R4 transmission.

When it comes to doing any sort of troubleshooting on a vehicle I think it is incredibly important to work from a most likely to least likely philosophy, but also weighing it against how difficult something is to get to and cost.  So let’s get into some common problems that the 700R4 may have.


Torque converter won’t lock

The 700R4 and 2004R were the first GM automatic transmission to come from the factory with a locking torque converter.  This allowed for a true 1:1 connection between the engine and rear wheels at high speed, which increased fuel economy.  If you feel that the engine seems like it is turning faster than it should be while going down the highway, than you could have an issue with torque converter refusing to lock up

Common causes:
It is caused by a switch under the brake pedal. You’ll find a couple of different wiring situations down there.  The first one that there is a combined switch down there that controls the cruise control, brake lights, and lockup converter.

The switch will be hot unless you press the pedal in, which is the exact opposite of how a brake light switch works, so it’ll do you no good to try and splice into your brake pedal wiring to fix this.  This is so if it goes out the torque converter doesn’t stay locked up, which would be way bigger of a problem.

If there is more than one switch down there, than you’ll want to either google your make and model and figure out which one it is.  Or, you can unplug one and see when if your brake lights still work.  If the lights still work than you know you’ve found your switch.

Most of the time the cruise control switch will do double duty with the torque converter lockup switch, so using process of elimination above that should get you to the part you need.

Now you may  want to make sure that the circuit is getting voltage.  You can do that with a test light.  If it’s not, you’ll need to make sure that you have checked that the fuse hasn’t gone out, or you’ve singed a wire.  This can often happen after you’ve installed an aftermarket stereo system.  All of these suggestions should cost you less than twenty bucks, and more than likely will be able to fix this problem.


700R4 not shifting right

700R4 Problem Diagnosis

The 700R4 is still a mechanically controlled transmission (with the exception of the locking converter circuit mentioned above), and depends physical pressure sensors and a sort of throttle position sensor to get it’s throttle position right.  This throttle position sensor is called the “TV Cable”  This cable acts like the kick down switch would on a TH350 in that it’s physical, but lets the transmission know exactly where the throttle position is like a 4L60E.  If you think that your TV cable may be going out, you can pick one up on Amazon for under thirty bucks here:  http://amzn.to/2kTO8lF

Here is a good video on how to install and adjust a TV Cable:


700R4 speedometer not working

The 700R4 uses both a traditional mechanical speedometer cable, like you might find in an older muscle car.  Alternatively, they also used a variable speed sensor.  This sensor is often abbreviated “VSS”.

Common causes:

The first thing you’ll need to know is which type of speed sensor you have.  If you can safely get under the car and take a look around the tail-shaft.  If the cable coming out of it is thick with a big circle that screws into it, you have a mechanical speedometer.

Try replacing the speedometer cable.  Unless the speedometer itself is broken, this will most likely fix it.

If there is a wiring harness that plugs into something back there, you have a VSS.  You’ll need to determine if the wiring is getting voltage.  If it is you’ll need to replace the VSS on the tail shaft, or the speedometer itself.  Of course, you could get lucky and it’ll just be a wiring issue.


Engine revs, but the car hardly moves

This is either low transmission fluid or a problem that is going to get end with you at the transmission shop, and no more college savings for your kids.  Have you noticed the transmission puking fluid when you park it?  If so you need to fill it back up and find where the transmission is leaking and fix it.

Here is a whole post on low transmission fluid that may help.


Bad vibration

If your 700r4 is having a problem with harsh vibration going down the road, it’s more than likely loose torque converter bolts, or a driveshaft that needs balancing.


700R4 won’t shift

This is often a sign of a bad governor gear, or a TV cable that is not returning back when you let off of the throttle.  Here is a pretty good resource on this subject.  This is a pretty advanced problem for a shade tree mechanic and may be another one that you leave up to the professionals.



No matter what your level of confidence with your mechanical skills, there are many 700R4 transmission problems that you can fix all on your own.  Good luck and thanks for reading.


Posted in tech