2000 s80 trouble codes p1618, p0751

2000s80kevin · Post by **2000s80kevin** » 12 May 2014, 17:40

I had the abs module repaired and works great, all the lights went away. I also had no high gear and put in a shift solenoid kit. Now I still have no high gear and I'm getting these codes p1618, p0751. Do I have a software problem? Or is it terminal? Any thoughts will help. Thanks

Post by **Oly_850** » 13 May 2014, 15:00

P0756 and p0751 are set when the trans control module commands a shift to a gear and it doesn't happen. No 4th gear is a common problem on these GM 4T65EV-GT transmissions caused by a burned third clutch and / or the splines on the fourth gear input shaft being worn completely off. I replaced all of the solenoids in mine to no effect. I'm pulling the trans for a rebuild next weekend. Unfortunately, around 130k these units just die in one of a couple ways and a rebuild is really the only solution. GM improved the shaft and hardened the splines in 2003.

2000s80kevin · Post by **2000s80kevin** » 14 May 2014, 18:02

I was afraid of that, I just figured since it is in drive and shifts fine to 3rd and does not try to shift again that it was electrical. You would think if the shaft was gone it would shift but not go. Thanks

Post by **Oly_850** » 19 May 2014, 09:03

Oh it's trying to shift, you just can't detect it without VIDA and DICE box, the TCM and ECM compare notes on the expected and actual gear ratios and has a stroke when they don't match. The fourth gear clutch likely engages, spins the shaft and exactly nothing happens because there's no teeth left to spin the next component , so it defaults to 3rd gear, lights up the transmission service code / indicator and there you have it.