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My 2001 GMC 2500HD 8.1Liter Allison 1000 transmission will…

My 2001 GMC 2500HD...

My 2001 GMC 2500HD 8.1Liter Allison 1000 transmission will not shift passed 3rd gear. Plugged in and got a lot of codes showing & they will not clear. P0700, 0727, 0742, 0840, 0841 0845, 1709, 1710, 1711, 1713, 1779. Not sure what to do. Thinking of replacing Control Mode. Truck been sitting for a few years.

Mechanic's Assistant: Have you checked the level of your transmission fluid? Is it bright red, or is it dirty?

Yes replaced all the fluids on truck - transmission fluid was very clean (pink) very little debris on magnet.

Mechanic's Assistant: What is the model of your '01 GMC?

2500 HD 4x4, 8.1 liter

Mechanic's Assistant: Are you fixing your 2500 yourself? What have you tried so far?

Yes with a mechanic. The shift cable was bent & we replaced it.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Not sure where to go from here. Thinking of replacing transmission control modular - since we can not clear codes & have so many. Not common.

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Answered in 24 minutes by:
3/27/2018
Todd Audette
Todd Audette, A.S.E Certified Master Technician
Category: Transmissions
Satisfied Customers: 427
Experience: GM Transmission Technician
Verified

Hello, my name is***** to Just Answer! I will be assisting you with all of your vehicle questions today. Give me a few minutes to review a few things and i will be back with you shortly

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I would definitely be trying a TCM in this truck before anything else. But review this Bulletin too

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Customer reply replied 3 months ago
I assume the bulletin above is not a recall on this truck, just something that we may have to do if the TCM does not fix the problem. Looks to be a pretty major job.

Yes not a recall just a service bulletin as a possibility....The reason i attached it was because there's a lot of the same codes that you have

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Todd Audette
Todd Audette, A.S.E Certified Master Technician
Category: Transmissions
Satisfied Customers: 427
Experience: GM Transmission Technician
Verified
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