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The 4L70E automatic transmission is undoubtedly a workhorse gear mechanism that offers more excellent reliability and a good deal more power. Read on for specs and more information.

The 4L70E is a 4-speed automatic GM transmission with up to 5 gears, including reverse. The 4th gear of the 4L70E is a .70 overdrive. It also shares the same basic design – and case – with the 4L60E and the 4L65E. This 4-speed automatic transmission is designed with considerably lightened materials to support much better fuel efficiency, electronically-controlled shifting, and four speeds. It is the last iteration of a unique design launched long ago, starting with the 700R4.

Here are the specs of the 4L70E:

  • Production: 1992 – Present time
  • Manufacturer: General Motors (GM)
  • Torque Converter Lock: Yes
  • RPO Code: M70
  • Overdrive: Yes

Outer Case Material

  • Aluminum + 2 removable bellhousing
  • Controlled by Computer: Yes, via the engine ECU.

Gear ratios are as follows:

  • First gear: 3.06
  • Second gear: 1.62
  • Third gear: 1.00
  • Fourth gear: 0.70
  • Reverse gear: 2.29

The 4L70E automatic transmission weighs approximately 133 lbs. dry.

The Unique Differences Between the 4L70E and 4L60E

There are several differences between the 4L70E and the 4L60E. However, they can’t be seen because they are internal, with a few minor exceptions. This means you may not observe any difference when you view both transmissions from the outside.

For instance, the output shaft is different, and the 4L70E now bears an input shaft speed sensor. 

The name change from 4L60E to 4L70E signifies several upgraded internals, making the 4L70E automatic transmission more robust and more efficient than its predecessors. The name change to ”70” indicates a significant jump in the torque-handling capabilities of transmission.

Here are some of the few – but significant – structural improvements that have been made to the 4L70E, which has boosted its reliability and efficiency over its predecessors:

  1. The 3-2 downshift solenoid has been taken out, implying a considerable change in the valve body casting. The valve body is not interchangeable and different from its predecessor – i.e., the 4L60E – since the 3-2 solenoid location has been cast shut.
  2. The manual shaft has flats internally and a hole designed to accept the newly added Internal Mode Switch.
  3. The schematics, as well as internal wiring, have been changed entirely. The connector pin in this automatic transmission is far different from the ones found in its predecessors.
  4. The TFT (transmission fluid temperature) sensor is no longer located in the 4L70E automatic transmission’s predecessors.
  5. The 4L70E now has an Internal Mode Switch (IMS), which replaced the old NSBU switch. The NSBU was external, while the IMS was internal.

Other minor changes include the total removal of the Parking rod and pressure switch. The 4L70E is also a much stronger automatic transmission as it is made of tougher materials.

The 4L70E and the 4L60E transmissions look very much alike, except for the differences in the internals. Swapping parts from one to the other is a very poor decision, primarily if you don’t ensure that those components share the same GM Parts number.

In other words, don’t even think about it. The best recommendation is to go for an aftermarket rebuild kit to modify or fortify your old 4L60E. You can’t convert the 4L60E to 4L70E.

How to Tell Two Transmissions Apart Without Opening Them Up

If you are looking for a particular transmission in stock GM automobiles, you can tell the 4L70E apart from the 4L65E without opening up both. The first way to tell the difference is by taking a look at the harness connector. The 4L70E transmission has a neon blue or black harness connector.

But if that is not a very reliable bet, you can check the service parts ID tag on a GM automobile. An ”M70” symbol should be o the tag, especially if the automobile’s stock transmission is a 4L70E. 

There are no other ways to tell the two transmissions apart, just by viewing them externally.

Can the 4L70E Replace the 4L60E Transmission?

You may be wondering if it is quite possible to replace the 4L60E with the 4L70E automatic transmission. Yes, it is possible: the 4L70E will bolt right in with some minor exceptions.

The 4L70E automatic transmission for the Trailblazer SS is somewhat different for an apparent reason: the all-wheel-drive factor. The torque converter for both transmissions is the same. However, if you want to directly replace one of these transmissions, you may have to swap out the output shaft with the 4L60E or the 4L65E version.

Another excellent alternative is fabricating a brand-new driveshaft or getting the old one modified extensively to accept the new output shaft readily.

The 4L70E Automatic Transmission: Built for Toughness

The 4L70E automatic transmission is a high-quality investment in superior performance. And installing it is not a plug-and-play business. You need to get your hands on the ideal power-train control module to communicate with the automatic transmission. In a few cases, you may have no choice but to re-pin the wiring harness.

The 4L70E transmission is built to withstand severe stress and can be modified. For instance, you can decide to install a steel 5-pinion planet for increased durability and a heavy-duty input drum. Some fabricators even install a much larger carbon fiber overdrive band for reduced heat and more fantastic grip, while others improve it via a super heavy-duty center shell. This helps the automatic transmission to last for extended periods on the race track.

Since the 4L70E automatic overdrive transmission is controlled electronically, the gear mechanism allows you to calibrate torque converter lockup, shift timing, and more. This makes the 4L70E much more versatile than the older throttle valve cable predecessor, the GM 4L60s.

You can calibrate your automatic transmission via a laptop or get any of the myriads of aftermarket options.

If you are looking for a pretty solid GM transmission within the 650 HP and ft./lbs. Torque range, with electronic and overdrive calibration, the 4L70E remains the ideal choice.

The Takeaway

The 4L70E automatic transmission is undoubtedly a workhorse gear mechanism that offers more excellent reliability and a good deal more power. Upgrading to the 4L70E automatic transmission is your best bet if you are looking for or require a transmission capable of working up beyond the realm of 425 ft./lbs. of torque and 450 HP and below the 650 HP and ft./lbs. of torque range.

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