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Message: <blockquote data-quote="gl55" data-source="post: 4166480" data-attributes="member: 729"><p>Here is the deal with the 6L80/90 transmissions. Up until 2014, the TCM commands torque converter clutch lockup starting in 2nd gear and up. Starting in 2014 it commands TCC lock up starting in 1st gear and up. But it is not a positive apply to the TCC clutch. It slips the lock up clutch 20 rpm when locked up and if equipped with DOD/AFM it slips it 40 rpm in that mode when driving. This causes over time the clutch lining to progressively wear away. Eventually the clutch material circulating in the fluid will eventually plug up the filter and end up starving the pump for fluid causing low fluid pressure and thus burning up the clutch packs and causes transmission failure. It seems to happen between  100K to 160K miles according to several transmission shops I deal with that rebuilds them. They all say the TCC clutch failure is the cause of 95% of the failures on those transmissions. What you can do to prolong the life of the transmissions with custom ECM/TCM programming is to set the calibration to keep the converter unlocked until only 5th and 6th gear from 50 mph and higher and 0 RPM slip. That also makes them drive better and feel more responsive.  Another thing you can do if you don't have access to ECM/TCM  programming is when they get to 75K-80K miles, drop the pan and change the fluid and filter and put in a new GM torque converter. Doing that wil remove almost all of the contaminated fluid in the transmission as just draining the pan only removes about 1/3 of the fluid as about 2/3 if the total fluid stays in the torque converter and you will start out again with a new TCC clutch. That will be  cheaper than a complete rebuild.</p></blockquote><p></p>

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