Trans Problems - Need help for a friend ASAP

Mopar440_6

Mopar440_6

New member
Joined
Feb 13, 2008
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205
Not having much luck searching through the forums. I'm a 12V Cummins guy so I have no idea when it comes to the Dmax/Allison trucks. A friend has a 2002 Chev. 2500HD 6.6L Allison truck in the shop that is having major transmission problems. Starts and runs fine. If you put it in gear it'll move in reverse but it stops working altogether after a 5 minute warm up. I'm guessing it's in limp mode but not sure why. Its throwing the following codes:

-P0500
-P0700
-P0731
-P0733
-P0776

All I've found so far is that it might be the e-shift valve, NSBU switch, bad PSM, or the trans just needs rebuilt. Any help or suggestions on where to start with diagnostics would be greatly appreciated. Thanks.
 
this is probably redundant but:

p0500 = vss malfunction
p0700 = trans codes present
p0731 = 1st gear incorrect ratio
p0733 = 3rd gear incorrect ratio
p0776 = pressure control solenoid B stuck 'off'

Has it been chipped? Worked to death? Does it slip? Any messages in the DIC about the trans? If you clear all codes, will it behave?

p0776 is supposed to be the code of death. if it doesn't behave after all codes are cleared, i'd tend to start thinking it is in bad shape.

How many miles? when does it do this?
 
I've been told 0776 is a tie up which is the last code you want to see. Also the incorrect ratio codes indicate it's slipping
 
Well, I finally got a chance to go take a closer look at the truck today. Forgot to write down the miles but my friend said its close to 200K. No chip that I could find but it seems that it has been run pretty hard. Trans is slipping some. Supposedly the dealer reset the codes and changed the trans filter about 2 months ago and it behaved for a while. Did some more diagnostics but still don't have anything definitive. Friend and I are guessing its going to need a new trans...
 
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