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Discussion Starter #1
I have an 11 lml and it's pulling codes (randomly) p0880, p1762, p0563. The truck will drive fine, and then it feels like it's in and out of gear, shifting very harshly. If I'm driving at parking lot speeds sometimes the wheels will lock up, and if it will move sometimes it feels like individual tires are having brakes applied, or as if I'm in 4wd turning full lock. I'll get shift inhibited and nothing I do fixes it. While the truck idles the idle jumps around from about 650 to 900. It feels like it's adding rpm to put the truck in gear. Whether I leave the truck on or have it off, the problem goes away in about 30 minutes and then the truck drives fine. It's doing it right now but when I hook up my Autocal it won't pull any codes at all. When I try to change tunes on the Autocal I get the $0502 error. Prob ably not related, but never had any issues with it until the drive train started acting funny, so who knows. Truck is deleted, running efi live from synthetic. Any ideas?
 

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Discussion Starter #2
My trans temps also sit around 110 most of the time and I feel that they are higher while it's acting up, around 150.
 

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The TCM onn the 2011 Allison seems like they have a high failure rate- must be made in China. I have heard of several hundred bad units.
 

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Well I'm hoping that's what I have on my hands. I started a thread about my issues and guys pointed me in that direction. Hoping to hear from the OP what resolved his issues becasue mine are the exact same.

Weird how it can just up and quit working. Was running fine.
 

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Mine started acting up today as well. Disconnected the batteries for 30 minutes. Ran just fine up to the autoparts store to use the OBDII scan tool (CEL on). Had the PO880 code. Cleared the codes, turned off the key. Returned the scan tool. Jump back in the truck and it acts like it is stuck in 4th gear. Will be ordering a new TCM.
 

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sent the TCM off to Autocomputer Specialist in FL. HUGE mistake! They claimed my TCM was problem free. Charged me $150 and then shipped it back the SLOWEST possible way they could and charged me double what 2 day USPS charges. Still ended up with the U0101 and the P0880 codes.

Took the truck to Chevrolet. They discovered the TCM was bad. Ordered a new AC Delco unit from Rock Auto ($270). $145 to program the new unit. Truck drives remarkably well. No CEL.

I would steer clear of Autocomputer Specialist. I have reached out to them asking for my $$ back....
 
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