My 01 Duramax set for 5 days while I was on a business trip. When I returned I hooped in it started it up idled for a minute or so and back up my drive way. When I put in Drive it wouldn't go NO where. i put it in park & back & drive it went into gear but wouldn't shift. I stopped put it in park & shut it off. Restarted & everything was fine for a week or so. Now that its cold I have to set and WARM it up for a while or the same senerio starts all over again...HELP. Fluids are topped and filters changed w/ fluid 25k ago........what gives??

 

could be a several things, need to check for codes in trans, sounds like a temp sensor problem maybe something else

 

You need to get a hold of mike l or Eric from merchant.

 

How much power do you have in the truck? It very easily could be your converter starting to go or plates sticking from suction

 

I bought a truck a few months ago with a similar problem. The previous owner was convinced by the dealer that the transmission was out. So he took it to a local transmission shop to swap a salvage Allison. When they got into it, they discovered a corroded sensor (not sure where). They replaced it and it was good to go (less than $100 fix). So it might be beneficial to find an Allison specialist and see what they can find.