TCM on Allison in Freightliner Chassis

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New member
Jul 13, 2018
Hey guys, new to the group so "Hello from Texas"!  I've got a 2008 Tiffin Allego Bay Open Road with a 6.7L Cummins and Allison transmission.  Had a breakdown last weekend and the shop says it needs a new TCM.  Labor is ridiculous, so I've authorized them to purchase the new TCM and program it to my transmission, but I'll be installing myself.  From what I've seen online it should be a matter of unplugging two harness connectors and reinstalling with new TCM.  Anybody done this and able to confirm before I get it back only to figure out it's not that simple?

Gary RV_Wizard

Site Team
Feb 2, 2005
At our Silver Springs FL home
It appeared to be that simple on my 2004 coach (Allison 3000 tranny).  I never replaced the TCM, but had a wiring harness issue and swapped the adjacent relays while troubleshooting and also unplugged and replugged some things.
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