2015 Chevrolet Silverado 1500 - Hard Shifting and P0700 Transmission Code

Question

My 6L80 transmission is acting up. It started with a 'clunk' when downshifting into 2nd coming to a stop. Now, it feels like it's slipping when I take off from a light, then it slams into gear. The Check Engine Light came on with P0700 (General TCM code) and P0796 (Transmission Control Solenoid C Performance/Stuck Off).

I dropped the pan and the fluid looked dark but didn't see huge chunks of metal, just a little fine 'fuzz' on the magnet. I'm trying to figure out if I need a whole new unit or if this is an electronic fix in the valve body.

MackMarty · Answer

✅ Confirmed fix: The problem was a failed TEHCM (Transmission Engine Horsepower Control Module) which houses the solenoids and the TCM. The Solenoid C was stuck due to a ruptured pressure switch diaphragm. Replaced the entire TEHCM assembly with a pre-programmed unit and installed a Sonnax line pressure booster kit to improve shift feel. The truck now shifts smoothly through all gears and no more P0796.

BigRigBenny · Answer

P0796 is often a sign that the 1-2-3-4 piston has cracked, which is a common failure point on the 6L80. If that's the case, a simple solenoid fix won't work because you're losing hydraulic pressure internally. You might want to pressure test the individual circuits.

2015 Chevrolet Silverado 1500 - Hard Shifting and P0700 Transmission Code

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