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.
Input Shaft Splines
Output Shaft Splines
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.
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.
Manufacturer: Ford Motor Company
Type: 3 Speed Automatic
1969 and older: 24 spline
1970: 26 spline
1971 and up
Torque Converter Lock: 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.
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.
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.
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.
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
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.
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 Manual
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.
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.
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
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
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.
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
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
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”.
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.
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.
The Saginaw four speed transmission is a transmission that was used in a variety of GM cars in the 60’s. They were popular in the Muscle Car era. As a rule of thumb, they were not built to handle the kind of power that a Muncie transmission could handle. So, if you are looking to drop one in a vehicle that makes more power than it did when it was stock, you should consider going a different way. That being said, you didn’t come here for my opinion about what to do with a transmission you could be very well looking at right now. Lets get straight to it!
Saginaw vs. Muncie identification
Far and away the easiest way of telling them apart is what the transmission is made of. The Saginaw was made out of iron. It usually found its way into trucks and other heavy vehicles where weight was not at a premium. The Muncie was made out of Aluminum. So and old Muncie will usually be smooth and a little greasy. An older Saginaw will usually be coated in rust unless it was cared for extra ordinarily well. There is quite a difference between them side by side. Have a look:
A lot of people just need to know which one is which, and the case material will provide you with fine answer to that question.
Another way to tell the identify a Saginaw transmission is to look at the shift arms. On the Muncie they are on the tail shaft, whereas with the Saginaw they are on the side of the case. Observe the picture above. You can see the shift arms right on the side of the case.
Saginaw four speed transmission identification codes
Also, one of the most common issues you may experience when looking at a Saginaw is whether or not you are even looking at a three speed or four speed version of the transmission. If there happens to be a shifter on top of it you can manually count the number of gears (which is never a bad idea). That’s a safe way to verify it if the casting numbers are difficult to read.
You’ll find the casting numbers on the main transmission case just after the tail shaft housing. The first letter in this number is going to tell you exactly which Saginaw transmission you have. You are looking of the letter R. If the first letter of the code starts with an R than you can be confident that you have found what you can be confident that it is a four speed version.
If it starts with an M you are looking at a Muncie, and if starts with an S you are looking at the 3 speed Saginaw. If you would like to read more about decoding a 1960’s transmission, this page is pretty good.
Saginaw 4 speed identification- figuring out the gearing
I’m not a big restoration guy. I don’t look for numbers matching pieces for my vehicles. So this way is going to help you narrow down exactly what kind of saginaw that you may have.
Count the rings: There are rings around the input shaft that will help you determine the gearing in the transmission itself. According to camaros.net, they are as follows:
No lines on the input shaft- First 2.84, Second 2.01, Third 1.34, Fourth, 1.00
1 Line- First 2.54, Second 1.84, Third 1.44, Fourth, 1.00
1 Line- First 2.54, Second 1.84, Third 1.32, Fourth, 1.00 <— Much less common
2 Line- First 3.11, Second 2.20, Third 1.47, Fourth, 1.00
3 Line- First 3.50, Second 2.46, Third 1.65, Fourth, 1.00
Good luck with your project, and thank you for reading.
Clutches are similar to brake pads in many ways. They are made of the same type of material, and they both wear out eventually. The good news is that although a clutch replacement costs more than a lot of vehicular repairs, it is nowhere near as expensive as having an automatic transmission rebuilt.
The number one factor in how much it will cost to replace your clutch is going to be labor. You have to take apart most of the driveline to get to it. This includes removing the driveshaft, starter, hubs (front wheel drive), and many more parts that’ll depend on the specific vehicle you plan on fixing.
Clutch replacement price factors
I spoke with several transmission shops and the consensus is that it costs between $500 and 1200 dollars to change out a clutch. Several factors affect the price. Let’s review them.
The price of the clutch and flywheel themselves- As a rule of thumb, your more common lower horsepower cars are going to have a
Labor costs– Labor costs will often make up the majority of the price for a new clutch. So, if you have a shop charging $80 an hour vs. one that is charging $130, your bill will vary wildly even if they are doing the exact same job.
How hard it is to get to your clutch– If you are bringing in a rear wheel drive vehicle, it generally is going to be easier to get to the clutch than a front wheel drive model.
Are you going to do the job yourself?- If this is the case, than you really only need to look at the cost for the clutch replacement parts, which can be less than a hundred bucks.
Dealer or mechanic?- A dealer is nearly always going to cost more money for the repair. The upside is that they are going to exclusively work with your make of vehicle. They also have a vast supply chain network, which means that any part that they may need will be available quickly, which means that you get your vehicle back quicker.
Clutch replacement time
The actual time that it takes to replace a clutch is minimal, assuming that you start with all of the parts needed to complete the job. A good shop will have a turnaround time of only a day or two.
Save money and do it yourself
It is certainly not an easy job. In fact, replacing the clutch can be one of the most challenging DIY projects that a shade tree mechanic might attempt. Don’t
If you are interested in doing the job yourself, you can certainly learn how from YouTube. Here is a guy with a great channel that will show you what goes into doing this on a front wheel drive vehicle. If it doesn’t scare you, than you may be able to save yourself some serious money. It is so much easier to do something like this when you can find a tutorial for your exact vehicle.
Make sure the job is done right
Before you commit your money to a repair, make sure that you are getting the job done right. A clutch replacement will last a heck of a lot longer if the shop is replacing the flywheel as well. For most shops this will automatically be written into your estimate, but just in case it is not, make sure that they are doing this as well. It is important to find a good clutch repair shop.
I was listening to an episode of Carcastwith Adam Carolla one time. I believe he was talking about finding the right guy to repair a dent in his car. He said something along the lines of you don’t want a guy named Ashton touching this thing. You want an old guy with a name like Duke or Walter. In the United States the manual transmission has never been less popular, and it’s getting more difficult to find a good clutch repair shop.
It can be really difficult to find where to get your clutch replaced when nearly all of the major shops don’t want to mess with them. It has gotten so rare for a transmission shop to have one come in that they don’t want to mess with it. It is expensive to train someone on how to deal change a clutch. It’s an entirely different process.
Clutch replacement labor cost
A clutch itself is not the most expensive item that you can buy for your car. In fact, many of them can run well below a hundred dollars at the parts store. Where you are going to spend most of your money is going to be on the labor cost.
“Most independent repair shops charge between $70-$90 per hour and most dealerships charge between $80-$125 per hour.”
Most mechanics use a database that shows exactly how many hours a job is supposed to take. They will bill you the samefor the job regardless of the actual time to complete the job. Never let them tell you they are charging you more because labor took longer than expected. That is on them. Now that you have this in mind, you’re going to need to do a little research, and a little math.
Get a few estimates and make sure to plug it into this formula:
(Labor Hourly Rate x Hours to Complete Job) + Parts Cost= Total Repair Cost
You can use this formula for each shop that you call. This will help you get an idea of how to get the best price. While the full rate Before you even so much as go in to get your first estimate try Googling how many hours to change clutch (insert your model here). It’s great if you can go in knowing about how long it should take.
How to pick a good shop
This may sound crazy, but I think one of the best ways that you can find a good clutch shop is to go to the yellow pages. I know it’s 2016 (or it was when I wrote this), but you want to find some old guy who has been doing this for a long time. That guy you are looking for has probably been in the book for a very long time. Just look up manual transmission repair, or transmission repair depending on where you live.
If you are finding yourself having a hard time, you can also try and find a shop that deals exclusively with foreign cars. Imported cars tend to have a higher percentage of standard shift models. These guys will be able to fix your clutch as well.
When is it clutch replacement time?
You’ll know its is time to replace your clutch if you run across the following conditions:
The smell of rotten eggs. Clutches will stink when they begin to slip. They often stink as they heat up.
If the engine revs higher all of the sudden while going down the highway, or if you have a heavy load, or if you are going up a rather large hill. These can be early warning signs that the clutch is failing you. On the other hand, if you smell burning oil you may be leaking oil onto your flywheel. Check your engine oil level and then look under where you normally park the car. Is their fresh oil?
If you have a really bad chatter or jerking feeling when you take off you may have a warped flywheel or disk. The grip is compromised and it will probably need replacement.
Just remember, price isn’t everything. If you get two quotes that are close, but the clutch shop guy tells you he’s done your make and model more times than he can count, go with that guy to repair your clutch.
The 4L80E Transmission is a fully computer controlled transmission that comes bolted to the higher horsepower and torque trucks. It is the overdrive successor to the 3L80(better known as the TH400 for most of it’s life). It is significantly larger than the 4L60E and if you compare the cases side by side it makes the smaller transmission look tiny. All of this extra room allows for added durability while retaining four forward gears and reverse. The 4L80E usually came behind the higher horsepower 2500 HD Silverado and Sierra twins.
If the 4L80E is only working in second gear and reverse, then it has gone into limp mode. It does this to protect itself from further damage when it believes that there is a potentially fatal error. It is really meant to get you to a safe place and have it looked at. Although second gear will absolutely scream down the highway, it’ll get you around town without much of an issue.
Here are some common issues that can force the transmission into limp mode. Solenoids are the most common cause, whether it is the TCC solenoid or a shift solenoid. Although it’s not very common for the wiring harness to be exposed, you should still visually inspect the harness for obvious damage and shorts. Here is a good 5 minute video on how to go about this. Honestly, wiring is a lot easier than many people think, and it is often what keeps the older guys from putting a more modern powerplant in their car.
You’ll also shouldn’t rule out an issue with the ECM, but that is definitely not where you should start. If you need to clear the trouble code, you can usually just shut the engine off and start it back up. You should have four four gears until the transmission senses that the issue has returned. If it detects a problem with the input shaft sensor, vehicle speed sensor, output shaft sensor, or one of the many shift solenoids it’s immediately going to bounce right back into limp mode.
Common 4L80E Problems
Torque Converter Not Locking Up: The torque converter on most modern automatic transmissions is made to lock up in order to allow for a physical connection between the engine and the rest of the drivetrain. This is achieved by placing a clutch in the torque converter that locks out the hydraulic torque multiplication benefits. This improves fuel economy and reduces emissions. This can be caused by a bad vehicle speed sensor, throttle position sensor, or cruise control wiring.
Ignoring Proper Maintenance: You’ll want to make sure that you are changing your fluids at the proper intervals. Nothing is more important to the life of the vehicle. You change the oil all the time, right? But, the same fluid soldiers on mile after mile. That is how the transmission was designed to work, but when it is time to perform the maintenance make sure you do something about it. That’ll help your 4L80E from having problems prematurely.
This short guide is will hopefully help you diagnose simpler Allison Transmission problems. Allison Transmissions have been around for a hundred years and have set the industry standard for durability. The odds are pretty good that you’ll never find your way here, but if you did lets get this figured out!
Limp Mode on Allison 1000
Modern Allison Transmissions come with a limp mode installed. This is a different shift table that allows the transmission to protect itself from catastrophic failure. You should always assume that this isn’t “bogus” and try and get your transmission. This limp mode locks the transmission into third gear, and keeps the torque converter from locking up. It also keeps the transmission from going into reverse! Keep that in mind. You don’t want to get stuck somewhere that you can’t back out of.
The limp mode is often activated by things an excessive of slippage by the transmission. Here are some common conditions that can trigger a limp mode situation.
Towing: If you are towing a heavy load (especially up a steep grade) you can often activate the limp mode. This is certainly can be an inconvenient time for this to happen. Third gear should pull a load fast enough on the highway, but it can be challenging to get a load moving.
Excessive Heat: If the transmission overheats, that can cause it to slip as well. If you are noticing this problem during hotter weather, you may be able to keep it from happening by installing a transmission cooler. They can be found cheap on Amazon and don’t require a lot of mechanical knowledge to install. Heat issues are the number one killer of this transmission. Do your best to protect the investment.
Performance Tune: Often, when people get an engine tune they don’t realize it should really be a driveline tune. Even just a little bit extra slip put into the tune, and an Allison Transmission can have problems. So if you’ve gotten a tune recently and you’ve found your way to this page try asking if they could take the tune back to the factory specs. It should solve the issue for you.
If you’ve experienced one of the issues above, it may very well be time for a rebuild. It could be a false positive. Either way, you’ll probably want to clear the trouble codes. The best way to do so is to get a code scanner and scan the code to wipe it. It will go away after enough engine on/off cycles where the problem is no longer recognized.
Common Allison Transmission Problems
Modern transmissions are computer controlled, but if you are working on your tank (they made transmissions for them in WWII) or your classic vehicle you may wish to take a look at the vacuum lines. If it’s shifting to early and bogging, you may have it in the wrong port. If it feels like it is shifting toward the engine red line you could have it hooked to the wrong port.
Make sure that you are performing the scheduled maintenance in order to get the most out of your transmission. Most GM automatics come from the factory with non-synthetic fluid. You should make sure that you are using Allison approved fluids and changing them when they recommend. It’ll help you prolong the life of your transmission. If you do that you may never even have Allison Transmission problems!!!