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Showing results for tags '8-speed transmission'.
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New Poster; greatly enjoyed reading the posts. My issue: 2019, 10K miles, 5.3, 8-speed, 4WD. Driving down the freeway at 67 mph with cruise and suddenly, the truck jerked hard, braked hard, lit up the dash with too many messages to read, but did not drop out of cruise control. I was then running at 4K RPM to maintain 60 mph. Got off the freeway, and discovered that I had no reverse, and what appeared to be 4th gear only (rev to 3000 RPM to get rolling). Called OnStar - they could communicate with the truck but got failure codes attempting to talk all the onboard systems - TCM, BCM, Airbag, engine - 30 minutes - and could not talk to the truck. Made it home (saturday night) let it sit till Monday morning and it started and shifted just fine on the way to the dealership. The dealer said it was the engine speed sensor and they replaced it and to come get my truck. When I did, the porter driving my truck ip only got to the edge of the service drive and stopped, engine revving. Complete trans failure - no forward or reverse gears. 3 weeks later, they say updated the TCM software per #19-NA-244: Harsh 3-2 Downshift During Closed Throttle Coast Down When Coming to a Stop- (Nov 1, 2019). There is a special note on this bulletin: Note: This calibration update will NOT address any other transmission shift or performance concerns. So, they can't reproduce the issue and have no idea how to fix it. Anyone seen similar issues, or this issue? Thanks!!