6T40 Valve Body Problems & Solutions

The 6T40 transmission is a 6-speed automatic that was first introduced for the 2008 model year, and was used in a number of front-wheel-drive GM vehicles. The 6 forward gear ratios are provided by three compound planetary gear sets, and control of the shifting is done through the use of a TCM that is integrated into the 6T40 valve body inside of the transmission. The 6 pressure control solenoids and on/off shift solenoid is integrated into a single unit with the TCM and are typically installed as a single unit. As long as it is properly maintained, this can be a very reliable gearbox. However, 6T40 valve body problems can still happen. In order to properly fix a 6T40 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 6T40 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.

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?

6T40 Valve Body Diagnostic Trouble Codes | DTC

6T40 Technical Service Bulletins | TSBs

TSB PI0376A – Flare or slipping on the 2-6 shift – 6T40 Transmission | 6T45 Transmission

2011 Buick LaCrosse – 2011 Buick Regal – 2011 Chevrolet Cruze – 2011 Chevrolet Equinox – 2011 Chevrolet Malibu – 2011 GMC Terrain (equipped with 4 Cylinder Engine and 6T40 or 6T45)
Problem – When this common 6T40/6T45 transmission problem occurs, the driver may experience slipping and/or a sudden flare/surge when the transmission shifts into or out of 2nd/6th gear.
Solution – This problem is often caused by debris blocking the opening on the channel plate and spacer plate that provides oil to the 2-6 clutch regulator valve. To correct the issue, the channel plate, spacer plate and valve body will have to be cleaned.

6T40 Valve Body Problems

Torque converter issues due to TCC regulator valve bore wear

Problem – Due to wear at the bore where the TCC regulator valve lives, the valve could become stuck resulting in a number of transmission problems.

If the TCC valve is stuck in the ‘apply’ position, the torque converter clutch will become extremely harsh in its operation. If the 6T40 TCC regulator valve becomes stuck in the ‘release’ position, then either the torque converter clutch won’t engage at all, or it will slip. Other symptoms include a P0741 DTC, transmission overheating and premature torque converter clutch wear.

Solution – If transmission overheating is suspected, then the transmission and valve body will have to be inspected for signs of heat related damage. To correct the root cause of the problem, the TCC regulator valve bore will have to be repaired (or the valve body casting replaced), and a revised or upgraded TCC regulator valve, shuttle valve and spring will have to be installed.

Transmission function issues related to excessive actuator feed limit valve bore wear

Problem – One of the more common 6T40 valve body problems is excessive wear to the AFL valve bore. This vital transmission part is used to regulate hydraulic pressure to the shift solenoids, and wear to the valve body bore where functions can cause reduced clutch pressure. This can lead to a number of transmission problems that include:

• Unusually harsh shifts
• Slipping
• Flared shifts
• Loss of 4th, 5th and 6th gears
• Complete transmission failure

Solution – The 6T40 actuator feed limit valve bore will have to be repaired (if possible) and a revised or upgraded AFL valve installed.

Clutch timing and control issues due to compensator feed regulator valve bore

Problem – In order to both smooth out the operation of the clutches and assist in the clutch apply timing, the GM 6T40 valve body utilizes a low pressure and compensator feed circuit. Over time, the compensator feed regulator valve bore can become worn and hinder the operation of the valve. This will lead to a number of transmission problems that include:

• Harsh gear changes
• Clunking sensation on downshifts
• Flared shifts
• Bumping on the 3-4 shift
• Binding
• Premature clutch wear
• Transmission overheating

Solution – If it’s possible that the transmission has overheated, then the internal components of the transmission, along with the valve body, should be thoroughly inspected for signs of heat related damage. The compensator feed regulator valve bore inside the 6T40 valve body will need to be repaired (if that’s not possible, the valve body casting itself will have to be replaced), and a new compensator feed regulator valve 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 6T40 valve body problems

The problem with repairing a 6T40 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 6T40 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 6T40 valve body almost a no-brainer. To learn more about the remanufactured 6T40 valve body and the remanufacturing process that Street Smart Transmission, 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