The GMC 2500 HD is designed to be an overly capable truck, for those who use their truck as a truck. Unfortunately though, Allison 1000 transmission used behind the Duramax diesel had its share of issues that could impact drivability. So let’s take a closer look and see if we can’t figure out why you should do about it.
What Transmission Do I Have?
The Problem
According to the technical service bulletin TSB 10-07-30-008B, which you can read right here, these issues affect the following models:
2006 GMC Sierra 2500 HD
2007 GMC Sierra 2500 HD
2008 GMC Sierra 2500 HD
2009 GMC Sierra 2500 HD
2010 GMC Sierra 2500 HD
2011 GMC Sierra 2500 HD
Of course, they need to be equipped with the Duramax diesel engine and Allison 1000 automatic transmission.
According to the TSB, drivers may experience the following symptoms:
Delayed engagement of, or slipping while in reverse
Transmission will not shift into overdrive
Erratic 4-5 shift
Stored DTC’s: P0733, P0777, P0735 and/or the P2723
The reason for these Allison transmission problems are the premature failure of the seals on the 3-5-R clutch piston. The piston and clutch plates themselves may also be damaged due to excessive heat and slipping.
What Transmission Do I Have?
The Solution
Obviously, the solution for this problem is to replace the damaged seals, piston and clutch plates. Problem is, to get the any of these parts, you’ve got to completely disassemble the transmission. So on one hand it makes sense to just go ahead and rebuild it. But you’ll be taking it back to stock form, which will include all of the factory design flaws. A remanufactured Allison 1000 transmission from a company like Street Smart Transmission on the other hand, won’t be taking it back to stock. In fact, it will be modified and upgraded to extend the service life. Annual come with a generous warranty as well. To learn more about this option, click here.
