6L80 / 6L90 Valve Body Problems & Solutions

First seen in the 2006 Corvette, the GM 6L80 transmission and it’s heavy duty twin the 6L90 transmission, were modern 6-speed automatic transmissions that employed a number of novel features like a 4-element torque converter and direct clutch-to-clutch shifting. On both the 6L80 valve body and 6L90 valve body, the TCM and valve body assembly are contained in a single unit located inside of the transmission at the bottom of the pan. All 6 pressure control solenoids and the 2 shift solenoids are contained in a single assembly with the TCM, which is called the Control Solenoid Body and TCM assembly. These tend to be relatively reliable transmissions. However as the miles rack up, 6L80 valve body problems and 6L90 valve body problems can happen. In order to properly fix a 6L80 / 6L90 valve body, it will have to be modified beyond it’s stock form, to compensate for the design flaws that cause all of these problems. Companies like Street Smart Transmission do a good job of modifying the 6L80 / 6L90 valve body (they do things like modify the bores to improve fluid flow and eliminate premature solenoid failure), that way the whole transmission can function the way it was actually intended. To learn more about their remanufactured 6L80 / 6L90 valve body, click here.

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

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6L80 Valve Body & 6L90 Valve Body Diagnostic Trouble Codes | DTC

Poor pressure control due to clutch select valve springs

Problem – Due to OE clutch select valve spring tension, the valve apply fluid pressure inside of the 6L80/6L90 valve body will be too high, causing a number of transmission problems that include:

• Premature failure of the 1-2-3-4 clutch
• Premature failure of the 3-5-Reverse clutch
• Non-functioning cruise control
• P0751 DTC

Solution – Install revised/updated valve springs

Pressure loss and premature clutch failure due to center support seal

Problem – Another common 6L80 valve body problem and 6L90 valve body problem is pressure loss and leakage due to age and mileage wearing away the integrity of the cente support seal between the case center support and the valve body casting. Some of the symptoms associated with this problem include:

• Line pressure leakage
• Loss of lubrication
• Overheating
• Clutch apply leaks for 2nd, 6th and Reverse
• Premature clutch failure

Solution – Transmission clutches, seals and hard parts will have to be inspected for signs of damage, if overheating is suspected. A revised center support seal will also need to be installed, along with repairing any damage found inside of the valve body.

Hydraulic pressure lost due to compensator feed regulator valve bore wear

Problem – The 6L80 valve body and 6L90 valve body use a low pressure compensator feed circuit to dampen the clutch return springs and smooth out the engagement and disengagement of various gears. Over time, damage can occur in the bore that houses the compensator feed regulator valve. This can result in a number of transmission problems that include:

• Line pressure loss
• Usually harsh shifts
• Clunk noise/sensation on downshifts
• 3-4 shift bump
• Flared shifts
• Binding
• Premature clutch failure
• Transmission overheating

Solution – The transmission will have to be carefully inspected for signs of damage if overheating is suspected. The valve body casting itself will also have to be inspected for signs of heat related warping and cracks. The compensator feed regulator bore will have to be repaired (if that is not possible, the valve body itself will have to be replaced), and a revised 6L80/6L90 compensator feed regulator valve, sleeve and spring will need to be installed.

Pressure instability due to wear in the boost valve bores

Problem – Excessive wear inside of the boost valve bores in the 6L80 valve body and 6L90 valve body can cause a number of transmission problems that include:

• Unusually hard shifts
• Delayed gear engagement
• Slipping
• Shifting behavior inconsistent with engine load
• Premature clutch wear
• Clutch pressure solenoid DTCs

Solution – The boost valve bores inside of the GM 6L80 valve body and GM 6L90 valve body will need to be repaired (if possible) and an upgraded 4-5-6 clutch boost valve, 3-5-R clutch boost valve, and 1-2-3-4 clutch boost valve will need to be installed.

6L & 6T Programming Problems

In this new global economy, General Motors, along with many other major manufacturers, have switched to “global platforms” that meet the government regulations in all markets. From emissions to safety compliance, these new global cars are saving GM a boatload of money because they only have to manufacture single components to be used around the world. An unfortunate byproduct of the GM Global A Architecture electrical system, is that Europe and Australia require automakers to secure vehicle modules in a single “environment” to prevent them from being used on other vehicles and ultimately sold on the black market. This theft deterrence measure also allows GM to simplify its diagnostic processes, which obviously saves them money. But all of that can create problems with programming and replacement.

The following modules cannot be swapped into another vehicle:

Engine Control Unit/ECU
TEHCM
Transmission Control Module/TCM
Body Control Module/BCM
Electronic Brake Control Module/EBCM
Vehicle Communications Interface Module
Hybrid Powertrain Control Module
Sensing and Diagnostic Module/SDM
Electric power steering
Instrument panel cluster
Radio

These modules are hardcoded with the vehicle’s VIN number, which allows the GM Global A Architecture to recognize the different modules on the network. There is no way to change the VIN number as there was before. Therefore, if a used 6L or 6T TEHCM is installed, the ECU will automatically command it into limp mode, where it will prevent the engine from starting, thus rendering it useless.

Installing software updates to a GM 6L or 6T TEHCM

Thanks to advances in manufacturing and technology, today’s transmissions are much more efficient than they have ever been. The downside of that is, the electronics now command the mechanical functions. Which means that software updates can often fix a mechanical issue. However, the GM Global A Architecture often prevents software updates to the 6L or 6T transmission. The technician may see a “program failed” error message when they go to install a software update to the TCM/TEHCM, at which point, the transmission will be in locked in limp mode.

This issue is sometimes caused by low battery voltage, a wiring issue, interference from aftermarket components, or an issue with the connection between the vehicle and the scan tool or pass-through device. It could also be that the new software/calibrations are not compatible with the TEHCM.

Common reprogramming diagnostic trouble codes

U0101
E4398
E4399
E4403
E4414
E4423
E4491
M4404
M4413

Reprogramming a GM 6L or 6T TEHCM

Because of how the GM Global A Architecture functions, it is now impossible to overwrite the VIN number programmed into the TEHCM. Which means a ‘blank’ TEHCM will have to be installed, in order to program it work with the vehicle.

Vehicles with the GM Global A Architecture include:

2010 – 2012 Buick LaCrosse
2010 – 2012 Buick Regal
2012 Buick Verano
2010 – 2012 Cadillac SRX
2013+ Cadillac ATS
2013+ Cadillac XTS
2012 Chevrolet Sonic
2011 – 2012 Chevrolet Cruze
2011 – 2012 Chevrolet Volt
2010 – 2012 Chevrolet Camaro
2010 – 2012 Chevrolet Equinox
2012 Chevrolet Orlando
2013+ Chevrolet Malibu
2013+ Chevrolet Spark
2013+ Chevrolet Captiva
2010 – 2012 GMC Terrain

Solving 6L80 / 6L90 valve body problems

The problem with repairing a 6L80 / 6L90 valve body is that you don’t really know what kind of stress and extreme temperature changes they have been subjected to. This is why many people simply install a remanufactured 6L80 / 6L90 valve body, to eliminate the threat of the unknown. Companies like Street Smart Transmission use state of the art equipment to completely remanufacture the valve body. This is not like rebuilding, where new components are simply installed into the existing valve body. They use specialized equipment to analyze each valve body to see if it has been cracked or warped. A mechanic does not just simply eyeball it, a machine does the inspection, and even checks the tensile strength of the metal to make sure that it meets the original OE specification.

Once a casting has been selected for the build, all of the bores are modified, to make sure that the valves will function the way they were intended to. Then every single component from the check balls, to the valves, pistons and springs are tested and/or replaced. After that process is complete and quality inspected, they install all new solenoids (they also bench test them prior to installation), speed sensors and pressure switches. The finished product is then put on a Superflow AXILINE Valve Body Tester, which can simulate actual road conditions. This allows their ASE certified techs to verify the functionality, and make any adjustments or fixes before they ship it out to the customer. Street Smart Transmission also gives it a 1-Year/No Hassle Warranty, which makes getting a remanufactured 6L80 / 6L90 valve body almost a no-brainer. To learn more about the remanufactured 6L80 / 6L90 valve body and the remanufacturing process that Street Smart Transmission uses, click here, or give them a call at 1-866-812-7560

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

GM Valve Body and TEHCM Part Number Table