All About the 4L70E

The 4L70E is a four speed automatic gm transmission.  It has five total gears including reverse. Fourth gear is a .70 overdrive.  It shares the same case and basic design with the 4L60E, and 4L65E.  It is also the final iteration of a design that started back with the 700R4.


4L60E vs 4L70E

Most of the differences between the 4L60E and the 4L70E are internal.  There are a few exceptions.  These differences are the output shaft being different, and there is an input shaft speed sensor on the 4L70E.  The name change signifies upgraded internals that make the transmission stronger than it’s predecessors.  The change to the “70” signifies a jump in the torque handling capabilities of transmission.

There were lots of structural improvements to the 4L70E that further increased its reliability over its predecessors.  The major changes include:

  • The manual shaft was given flats internally, and a hole to accept the added Internal Mode Switch.
  •  Added and IMS switch.  The Internal Mode Switch (IMS), replaced the old NSBU switch.  The IMS was internal and NSBU was external.
  • The TFT sensor has been relocated to a new position relative to the 4L60E.
  • Internal wiring and schematics have totally changed.  The connector pin is different than earlier transmissions.
  • The 3-2 downshift solenoid was deleted.  This meant a change in the valve body casting.  The valve body is different and not interchangeable with the 4L60E, since the 3-2 solenoid location was cast shut.  Here’s a schematic on the changes from Auto Service Professional.

Some of the more minor changes were the elimination of the pressure switch, and the Parking rod.  None of these new parts with the


Interchangeability with the 4L60E


These transmissions look exactly alike.  But, as listed above, they have many internal differences.  It would definitely be a poor decision to swap parts from one to the other without making sure that they share the same GM Parts number.  In fact, just don’t do it.  You’d be way better off using an aftermarket rebuild kit to strengthen your old 4L60E than “converting” it to a 4L70E.

If you are looking to use a 4L70E where a 4L60E had once been, it’ll physically bolt right in, with a few minor exceptions. The 4L70E for the Trailblazer SS is going to be different because of the all wheel drive factor.  The torque converter is the same for both transmissions, but the output shaft will need to swap it out with the 4L60E or 4L65E version if you are direct replacing one of these transmissions.  Another option would always be to have a new driveshaft made (or your old one modified) to accept this new output shaft.

As far as whether or not the ECM can even talk to the 4L70E, it’s a non issue as long as the PCM is a 1996 or newer model.  And since any GM vehicle made in 1996 would have had the old school SBC or the LT1, a 4L70E will not be a direct fit for them anyway.  The internal wiring harnesses are different.  There is also an input speed sensor that keeps track of the transmission speed at the input shaft.  This will not stop you from swapping.  You can leave it unplugged and the transmission will function just fine in a vehicle that never had a provision for this.

Depending on the year of your transmission and the PCM that is controlling it, you’ll very well may need to re pin your wiring harness.  This post is a great place to start.  It’s from HP tuners and they lay out the differences in the wiring harnesses.  You’ll need to lookup exactly what the pin layout is on your particular vehicle before swapping them if you are thinking of pursuing this avenue.


Here’s the takeaway


  • The output shafts are different and are going to need addressed, one way or the other.
  • 4L70E uses the same converter as its predecessor.
  • Don’t worry about the input shaft speed sensor.  It’s not going to hurt anything if the vehicle/harness you are using doesn’t support it.
  • You may or may not need to repin your harness.



4L70E Specs


Manufacturer:  General Motors
Production:  1992- Present Day
Type:  4 Speed Longitudinal Automatic
Gear Ratios:  

  • First- 3.06
  • Second- 1.62
  • Third- 1.00
  • Fourth- 0.70
  • Reverse-2.29
Torque Converter Lock: Yes

  Overdrive:  Yes

RPO Code:  M70
Outer Case Material:  Aluminum, with a 2 removable bellhousing
Controlled by Computer:  Yes:  Controlled by the engines ECU
Weight:  Roughly 133 pounds dry


4L70E Identification

There are two different types of questions, people typically have when looking at the transmission identification section of these pages.  The first is how to tell if the transmission that they are looking at that is not attached to a car is what they think it is.  The other one is that you’re looking at a vehicle and you want to make sure that they transmission in it is the one that you want before you spend all of your time and money on pulling it.  Both of these scenarios are covered directly below.

Scenario 1:  You are looking at a transmission outside of a car and want to know if you’ve found a 4L70E.

The 4L60/65/70E all share an identical case and number of pan bolts.  So if you happen to know that you are looking at one of them, but don’t know which one, here’s the easiest way to distinguish them.

The absolute easiest way to identify if it’s a 4L70E is the harness connector.  The outer part of it is going to be black or neon blue.  Below is a pic of the harness connector on the 4L60E.  Here is a link to a post that has a pic of a black 4L70E connector.  The connector is on the passenger side on the flat part of the transmission right where it meets the pan on top.  Next time I come across one I’ll update this page to include it.


4L70E Transmission Connector
Here is the connector on a 4L60E. It’ll be black or neon blue on the 4L70E.



Scenario 2:  You are looking at a car and trying to determine whether or not a transmission in the car is a 4L70E.


This scenario is much easier.  You’ll just need to look in the glove compartment and find the RPO code.  The 4L60/65/70E all used a different code for production.  You’ll be hunting for one of these codes.

M70 4L70E Identification
This tag is on the inside of all modern GM vehicles. Find one of the codes listed below to discover what transmission it has.


  • MD8– This is the 700R4.  Probably not going to come across this, but here it is anyway.
  • M30–  This is the standard 4L60E.
  • M32-  This is the 4L65E.
  • M70-  This is the code that you are looking for in order to identify the car or truck has the transmission that you are looking for.
  • MT1-  4L80E transmission:  The 4L80E is significantly bigger than the 4L60E and doesn’t look the same at all.


Wrapping Up

The 4L70E transmission is a bit of a rare bird, and not very common.  It’s not special.  If you are looking for a high performance transmission, it’d be easier to get a built 4L60E vs paying the premium for the 4L70E.  If you have anything to add, please leave a comment below.


You may also like:

4L60E VS 4L80E Differences

4L60E vs 4L65E Differences

4L60E Specs + Identification