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2011 chevy silverado 3500 6.6 duramax allison 2 w.d with delete
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Discussion Starter · #1 ·
I have a 2011 chevy silverado 3500 dually 2 wheel drive pick up with lml duraqmax & allison transmission. Transmission was working fine & never had issues but yesterday I came to a stop light & went to go after light turned green & trans was not in first gear & did not upshift. I got home & came out 10 minutes later & had no engagement in forward or reverse. It showed shift inhibited, shift to neutral to reset. I tried this a couple of times & it did nothing. Also the line under the shift indicator was blinking. I checked the fluid, condition looked good, started it back up & it worked perfectly. There are no codes & it still intermittently does weird stuff. Today I went to run errands & it was working fine, came to a stop light, light turned green & it was in 1st & wouldn't upshift. I drove it back to my business & let it set for about an hour, hooked up the scanner to look at data
& it's working fine. any ideas?
 

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Welcome to DieselPlace

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2011 chevy silverado 3500 6.6 duramax allison 2 w.d with delete
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4 Posts
Discussion Starter · #4 ·
I have a scan tool that can read data. I had it hooked up earlier today & of course the trans worked like it's supposed to.
 

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1997 GMC K3500 dually 4L80 4x4
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Yeah, that makes it tough. If it's broken, and you can't communicate with the TCM, I would suspect the TCM to be the problem. very common. PS don't let the tcm heat sink touch ground wile it's plugged in. I haven't tested it, but every duramax class I've gone to claims the tcm will be hurt if this happens. good luck. I would have my test points at the tcm power, ground and can circuits ahead of time so when the problem happens I can test quickly.
 

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2011 chevy silverado 3500 6.6 duramax allison 2 w.d with delete
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4 Posts
Discussion Starter · #7 ·
New tcm from Ryan's diesel solved the problem. Came already programmed & cost less than from GM .
 

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New tcm from Ryan's diesel solved the problem. Came already programmed & cost less than from GM .
Glad you got the issue resolved.
Thanks for giving us an update!
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2011 chevy silverado 3500 6.6 duramax allison 2 w.d with delete
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Discussion Starter · #9 ·
After watching the data on the scanner, everytime the tcm temperature would get over 130 degrees problems would arise.
 
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