6L90 transmission problems

In this brief guide, we are going to provide you with the common 6L90 transmission problems and what you can do to rectify these problems before they worsen.

6L90 transmissions manufactured by General Motors in 2006 were designed for RWD and AWD/4WD applications. This type of transmission had features such as clutch-to-clutch operation with a wide gear ratio for optimum performance and efficiency. We’ll mention a few common problems with these transmissions.

What are the common 6L90 transmission problems?

Most of the common 6L90 transmission problems are:

  • Slip in reverse or no reverse
  • Hard shifts to 3rd or 5th
  • Slip in 3rd or 5th gear
  • Slip or flare on the 2-3 shift
  • Transmission Fluid Over Temperature
  • Torque converter engagement/disengagement problems

Why is slip in reverse or no reverse a 6L90 transmission problem?

If the reverse gear is slipping or not engaging at all then there is definitely a problem with the 6L90 transmission as reverse gear is one of the most important gears in any vehicle. 

What signs are shown as a result of this 6L90 transmission problem?

If the reverse gear is not engaging at all or even slipping then this can itself be taken as a sign that the transmission is not functioning well.

How to fix this 6L90 transmission problem?

The shifting solenoids need to be checked and repaired also the engagement failure can be fixed by visiting a mechanic checking if there is a problem with the mechanical component or gear of the reverse gear in the transmission.

Why are hard shifts to 3rd or 5th a 6L90 transmission problem?

While driving on road if you experience a difficulty or complete failure while shifting from 3rd to 4th gear then your 6L90 transmission is surely having problems.

What signs are shown as a result of this 6L90 transmission problem?

While driving you will surely notice the shifting difficulty and in worst case complete failure for this problem. As this is a shifting failure, only while driving at the set speed and rpm you will notice this problem.

How to fix this 6L90 transmission problem?

Usually clutches are worn out and need to be replaced to solve this problem. Also in other cases it has been seen that clutch assemblies can be removed and rebuilt to solve this issue. 

Why is slip in 3rd or 5th gear a 6L90 transmission problem?

6L90 transmissions are not designed to slip and if you are experiencing slippage particularly in 3rd or 5th gear then it is definitely a sign of a problem with the mechanical components of the transmission.

What signs are shown as a result of this 6L90 transmission problem?

You will be able to hear the gear slip while driving and this would be itself a good sign if there is slipping. Also, an error code will be displayed if you use a diagnostic tool.

How to fix this 6L90 transmission problem?

The solenoids of the two gears might be worn out and need to be replaced. Also, there is a chance that these solenoids might also be broken. Rarely, complete mechanical failure occurs with these transmissions.

Why is slip or flare on the 2-3 shift a 6L90 transmission problem?

You would want a seamless and smooth shift even at low throttle input, so if your 6L90 transmission is slipping or flaring from 2nd-3rd gear even at high throttle then there is definitely a problem.

What signs are shown as a result of this 6L90 transmission problem?

You would immediately notice and sense if the 6L90 transmission is slipping or flaring from 2nd to 3rd gear as these are important gears.

How to fix this 6L90 transmission problem?

Firstly try replacing the transmission pressure sensor, if that doesn’t work then check for an oil leak in the servo assembly of the 2nd gear. These are primarily two fixes for this problem.

Why is transmission fluid overheating a 6L90 transmission problem?

Because transmission gears and shafts tend to get damaged, worn, and malfunction under high heat levels. This results in lower than the acceptable performance from the 6L90 transmission and high fuel consumption as well as lowering the life of mechanical components in the gearbox.

What signs are shown as a result of this 6L90 transmission problem?

A few common signs are slow response while accelerating and not getting the desired drive when needed. Also, you could see some sort of malfunction sign on the dashboard. 

How to fix this 6L90 transmission problem?

Check the transmission oil and its level. If it is too low then fill the required amount of oil in the transmission. If it is too dirty, then drain the entire oil from the transmission and fill it again.

Why is torque converter engagement/disengagement issue a 6L90 transmission problem?

The torque converter transmits the engine torque to the wheels via the transmission. If the parts of the torque converter are not engaged within themselves properly then the transmission malfunctions and the power is not delivered efficiently.

What signs are shown as a result of this 6L90 transmission problem?

Firstly you would be able to move the car forward when pressing the throttle pedal for disengagement problem and secondly for engagement from even if you press too much throttle the car will not move forward. 

How to fix this 6L90 transmission problem?

If the clutch of the torque converter is worn out then you need to replace it or else the solenoid might be broken which also might need replacing. In the worst case the entire assembly needs to be replaced if the state of the torque converter is beyond repair.

How to diagnose these common 6L90 transmission problems precisely?

As most of these problems can be felt while driving you can tell immediately the cause of the problem. If you want to pinpoint the cause then you can use a software diagnostic tool to be plugged into your transmission control unit but it is recommended to use one as written in the manual.

How to prevent getting these problems in the first place?

Regularly changing your gearbox oil and other lubricants may save you a lot of trouble and money in the future. Although many experts suggest different number miles for servicing, your car manual will give you a proper recommendation when you should change it. 

FAQs: 6L90 transmission problems

Is 6L90 a good transmission?

The 6L90 transmission is a high-performance transmission capable of handling up to 700 horsepower. Along with the 6L80 model, this transmission powers the best cars and trucks that GM offers.

What is the difference between 6L80 and 6L90 transmission?

The main difference between the two transmissions is the strength of the internal parts. The 6L90 transmission case is slightly longer, which provides extra room to house two additional pinion gears.

Conclusion

In this brief guide, we provided you with the common 6L90 transmission problems and what you can do to rectify these problems before they worsen.

If you have any questions or comments please let us know.

Citations:

https://atracom.blob.core.windows.net/gears/2011/2011-12/2011_12_20.pdf

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