6T70 / 6T75 Valve Body Problems & Solutions

First launched in 2007, the 6T70 & 6T75 transmissions were the result of a $720 million joint venture between General Motors and Ford. These two titans of the American automotive market join forces to create a new front wheel drive transmission that both companies could use. GM’s version of this 6-speed automatic was used in a variety of midsize cars and crossovers (an all-wheel-drive version of this gearbox was also made), from the Pontiac G6 to the Buick Enclave SUV. The 6T70 transmission was rated at 315 hp and 280 lb-ft, while the heavier duty 6T75 transmission could handle the same 315 hp. But it could withstand a more robust 300 lb-ft of torque. To improve performance of the transmission, the TCM is integrated into the valve body inside the transmission. However, 6T70 valve body problems and 6T75 valve body problems do still happen. In order to properly fix a 6T70 / 6T75 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 6T70 / 6T75 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 6T70 / 6T75 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.

What Transmission Do I Have?

6T70 Valve Body & 6T75 Valve Body Diagnostic Trouble Codes | DTC

6T70/6T75 Technical Service Bulletins | TSBs

TSB 13120A – Torque converter clutch sticking – 6T70 Transmission | 6T75 Transmission
2013 Buick Enclave – 2013 Cadillac SRX – 2013 Cadillac XTS – 2013 Chevrolet Malibu – 2013 Chevrolet Traverse – 2013 GMC Acadia – 2013 GMC Terrain
Problem – The torque converter clutch solenoid can stick due to debris in the transmission. When the vehicle is at the end of a coast-down, as the vehicle is coming to a stop, a stuck solenoid will fail to release the torque converter clutch. This keeps the engine directly connected to the driven wheels. As the vehicle stops, the engine speed will be pulled down below normal idle speed and the engine may stall. The vehicle can be immediately restarted and driven.
Solution – The valve control solenoid should be replaced, and the transmission control module will have to be reprogrammed in order to correct the problem.

6T70 / 6T75 Valve Body Problems

Pressure loss from worn hydraulic circuits

Problem – As the various valves, pistons and checkballs move around inside of the 6T70 valve body and 6T75 valve body, the metal casting can wear out and allow hydraulic pressure to be a lost. This can lead to a number of valve body problems including:

• Loss of line pressure
• Burnt clutches
• Erratic shifting behavior
• TCC clutch function issues
• Torque converter clutch related DTCs

Solution – Repair or replace the valve body and self and install new pressure switches, accumulators, valves, checkballs, springs and other internal components.

4-5-6 accumulator piston failure

Problem – Another one of the common 6T70/6T75 valve body problems is the failure of the 4-5-6 accumulator piston. This is extremely important transmission part is responsible for smoothing out the engagement of the 4-5-6 clutches. However, excess wear in the bore, and to the piston itself cause a number of transmission problems including:

• Harsh and/or delayed 3-4 shifts
• Slipping
• Burnt clutches
• Gear ratio DTCs

Solution – Repair bores or replace both the valve body casting itself and the accumulator pistons.

Excess bore wear

Problem – Yet another common issue with the GM 6T70 valve body and 6T75 valve body, has to do with excess bore wear inside of the casting causing pressure leaks, which then leads to a number of transmission problems including:

• Unusually harsh shifts
• Unusually soft shifts
• Premature clutch failure
• Solenoid DTCs

Solution – Repair the bores or replace the valve body itself, then install upgraded internal components to compensate for the wear characteristics of this transmission.

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 6T70 / 6T75 valve body problems

The problem with repairing a 6T70 / 6T75 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 6T70 / 6T75 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 6T70 / 6T75 valve body almost a no-brainer. To learn more about the remanufactured 6T70 / 6T75 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