6L90 MYD Transmission Guide (Meaning, Fails, Buying Used)

Transmissions are not all the same. Some car making companies know how to build transmissions. GM is one of those companies. It owned Allison before selling it, but before then it turned that company into a grade A transmission building company with a stellar reputation

The 6L90 MYD transmission is a 6-speed automatic transmission that was built and installed in some of GM's rear wheel and rear biased all-wheel drive vehicles. It is supposed to be a superior device that saves fuel and is electronically operated.

To learn more about this transmission and its specs, just continue to read our article. It has the information you want to know about when you are thinking of buying a GM vehicle that has this transmission installed.

What is an MYD Transmission?


The letters are actually a production code and do not really refer to anything else. The proper way to describe this transmission model is to call it by its actual name, 6L90.

This transmission is part of the 6LXX transmission family. This series of transmissions is designed to be fuel efficient and helps you save money. It is electronically controlled for maximum shifting and it has a unique output gear configuration that provides the device with a wider range of ratios.

The design enables this transmission to be customized to provide optimal fuel economy while providing top acceleration. Its 6.04:1 ratio spread gives you a great first gear and a top overdrive that cuts highway RPMs when you are cruising.

This transmission was created, designed, and developed by General Motors which usually has a top transmission building reputation. Part of that reputation was built through their ownership of Allison who is a premier transmission building company.

With GM’s knowledge, they did not need Allison anymore, so they sold the company and focused on building their own transmissions that would work best for their vehicles. The 6L90 has been around since 2006 approx.

It is seen as an improvement over the 6L80 model but is installed in a limited number of vehicle models.

Upgraded Features Of The 6L90 MYD

The 6L90 is an upgrade over the 6L80 transmission and inside this transmission, you will find the following features:

1. Modular features- this includes upgrading the hydra-matic design of the 6L80. There are 3 gear sets utilized in this upgrade, one input and 2 outputs which aid performance and give you the shifting power you are looking for.

2. Performance Algorithm Braking- This is not a universal application but its duties include monitoring the driver’s habits and learning the optimum speeds to up and down shift.

3. Driver Shift Control- This feature allows the driver to shift gears but without a clutch just like he would if he had a manual transmission instead of an automatic.

4. Advanced Control System- This feature monitors transmission performance and then makes adjustments for normal wear when components like the clutch plate start to lose their original form.

What this feature does is ensure that you get consistent performance from the transmission over its lifespan.

Other possible features that are or can be included are:

- Multiple Shift Patterns (Selectable)

- Driver Shift Control (Tap Up / Tap Down)

- Enhanced Performance Algorithm Shifting (PAS)

- Selectable Tow / Haul Mode

- Engine Torque Management On All Shifts

- Altitude and Temperature Compensation

- Adaptive Shift Time

- Neutral Idle

- Reverse Lockout

- Automatic Grade Braking

- Additional Features


- Integral Electro/Hydraulic Controls Module (Tehcm)

- Control Interface Protocol – GMLAN

6-speed Transmission What Does MYD Mean?


The best answer we have found for those letters is that it is just a production code. It means something to GM but it has no retail or customer value. Any website, etc., that talks about this transmission does not explain the code nor refer to it in its content.

We checked an acronym website and these letters do not appear or are explained in relation to the automotive industry. Most of the definitions refer to some aspect of the medical field and one airport code- Malinda Airport.

You really do not need to know the meaning of those letters. It has no automotive significance either. It is just an identity acronym that helps separate this transmission from other models made by GM.

If this answer does not satisfy you, you can always ask a mechanic or GM dealer for the meaning. But chances are they do not know either.

6L90 Gear Ratios

To gives you an idea of what to expect when you climb behind the driver’s seat of the vehicle with this transmission model inside. Take special note of the transmission fluid it uses. You do not want to change the fluid to a lesser option.

First: 4.030

Second: 2.360

Third: 1.530

Fourth: 1.150

Fifth: 0.850

Sixth: 0.670

Reverse: 3.060

Maximum shift speed: 6200 rpm

Maximum Validated Weight (GVW): 15000 lb (6803 kg)

Maximum Validated Weight (GCVW): 21000 lb (9525 kg)

7-position quadrant: P, R, N, D, X, X, X (X = available calibratable range position)

Case material: Die cast aluminum

Shift pattern: (2) Three-way on/off solenoids

Shift quality: Five variable bleed solenoid

Torque converter clutch: Variable Bleed Solenoid ECCC

Converter size: 300 mm

Fluid type: DEXRON VI

Fluid capacity with 300 mm converter: 13.0L (10.8 kg)

Pressure taps available: Line pressure

6L90 Specs


Maximum engine power (gasoline, truck): 452 hp (337 kw)

Maximum engine power (diesel, truck): 300 hp (223 kw)

Maximum engine power (passenger car): 555 hp (414 kw)

Maximum engine torque (gasoline, truck): 531 lb-ft (720 Nm)

Maximum engine torque (diesel, truck): 520 lb-ft (705 Nm)

Maximum engine torque (passenger car): 550 lb-ft (746 Nm)

Maximum gearbox torque: 885 lb-ft (1200 Nm)

6L90 vs. The 6L80

The 6L80 came first but it was not designed for all applications or all GM vehicles. The company needed something for heavy-duty applications so they came up with the 6L90 transmission.

The 6L90 shares about 75% of its parts with the 6L80 but it is not the same transmission. It has 6 pinion gears which is 2 more than the 6L80 as well as a strengthened input and output gear sets.

In addition to those improvements, the 6L90 has an extra clutch plate per gear enabling it to handle heavy-duty applications. If you do not need a heavy-duty transmission, then the 6L90 comes in a model without those extra clutch plates.

Then the 6L90 is about 35 mm or 1 3/8th of an inch longer than the 6L80 and also has more fasteners between the transmission and transfer case to cut down on vibration and noise in the drive line.

Other than that, you should see some similarities between the two transmission models. The biggest difference between the two transmissions is that the 6L90 is built tougher and should withstand more stress than the 6L80.

This extra construction enables this transmission to handle those heavy-duty applications.

Finding a 6L90 MYD Transmission Used For Sale


The last place to look and it is more of a desperate last-ditch effort, is to check the junk and salvage yards. In many cases, those companies receive badly damaged vehicles with the transmission in top shape.

You can see what they have available but do not count on them having a large selection. The next place to look will be eBay or internet classified ads. People are always looking to get rid of old parts to make extra money.

Those two outlets are the perfect resource for them. They can advertise and wait for someone to contact them. Often you will see motivated sellers in the latter of these two options.

One of the better places to look would be dealers. They may be able to order a new transmission for you and install it in your vehicle. You would have to check with them as installation will probably be part of the deal.

Finally, you can go to transmission and vehicle parts outlets. Quite a few popped up in a quick internet search. This transmission is supposed to be made currently so finding a replacement transmission should not be very hard to do.

Many of these outlets sell used or rebuilt 6L90 transmissions that should work well. The Internet will help you find one of these shops near you.

What Causes The 6L80 To Fail?

This transmission was built by GM for GM applications and those applications included AWD/4WD and RWD. Unfortunately, it was not a heavy-duty type of transmission thus it had many faults that caused it to fail during normal driving habits.

Some of those problems include but may not be limited to are:

- Cracks in the 1-2-3-4 pistons

- Slipping 2nd and 3rd gears

- Cracked drum

- Skipping 2-3 gears

- Clutch Failure

- First Gear Slipping

- Reverse gear engagement failure

- Cracked clutch drum

- Stator support issues

If you want a full explanation as to why these parts failed, you can click here. The explanations are too long to synthesize down to fit here. However, this list does not mean that everyone who owns a vehicle with this transmission will experience these problems.

It is still a good device that has held up well over the years. It is just not built for heavy-duty applications.

What Causes The 6L90 To Fail


This is a tougher upgraded transmission over the 6L80 and the list for parts failing is not quite as long as it is for that earlier model.

1. The reverse gear fails to engage- the fault is due to a Park straw which is a little metal piece that stops the car from rolling. Or it may be a bad clutch, in either case, replacement is your fix.

2. Gear slippage- This happens in reverse as well as between 2nd and 3rd gear. The source for this problem is a cracked 2-3-3/5-R drum. Replacement is also your fix here

3. First gear slippage- the source for this is either the solenoid is stuck in the off position or the valve body is preventing fluid from reaching the valves. The solenoid can be repaired but the valve body needs to be replaced.

4. Transmission overheats- the source for this problem is either dirty fluid or not enough transmission fluid. Add some fluid or replace it are your repair options.

What Vehicles Came With 6L90E?

This is the short list of vehicles you can find with this transmission. A longer list with the type of engine the vehicle came with can be found at this link. The difference between the two lists also includes the model numbers for the vehicles.

This list has those model numbers while the other one does not.

- Chevrolet Silverado

(2500HD and 3500HD with 6.0L engines- 2007-2014

- GMC Sierra

(2500HD and 3500HD with 6.0L engines- 2007-2014

- Chevrolet Suburban (2500) 2008-2013

- Cadillac CTS-V 2009-2013

- Chevrolet Camaro ZL1 2012-2015

- Chevrolet Silverado

(2500HD and 3500HD with 6.0L engines) 2015-2019

- GMC Sierra

(2500HD and 3500HD with 6.0L engines) 2015-2019

- Chevrolet Silverado

(2500HD and 3500HD with 6.6 L8T engines) 2020-present

- GMC Sierra

(2500HD and 3500HD with 6.6 L8T engines) 2020-present

{sources for all the technical information and vehicle application come from this link}

Some Additional Words

Is the 6L90 transmission any good? Yes, it is. It is a superb transmission that performs well for RWD and AWD vehicles. It is also a great device when it comes to fuel efficiency. You should save some money on gas when you own a vehicle with this transmission.

Then finding one of these transmissions is not that hard to do. If you know your way around transmissions, you can find and buy a 6L90 rebuild kit. Or you have the option of buying used or a professionally rebuilt transmission.

While it is not a perfect transmission, you should still benefit from its sturdy construction and low noise output. The acceleration is nothing to sneeze at either.

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