I have a 2005 3/4 to Duramax 4x4 crew cab with an allison Trans. It has a Fabtech 6" lift and 35x12.50x16 Mud Grapplers. The dealership included a Diablosport Preadator to correct the Speedo for the tire size.

I am having a problem that is driving me nuts. Every now and The trans seems to lock up at either 30mph or 60mph. It loses power and the cruize control won't work. I will pull over shut down the truck wait at least 5 mins then start it up and It won't do it again for the rest of the day. It only does this rarely.

I figured it could be a Speed sensor causing this issue but I don't know for sure. It hasn't thrown any codes and I have checked this every time it does it. My final resort isthe TCM but I am unsure if there is one on this truck. I can't remember if the Shifts are controlled by the pcm or by a TCM.

In my 00 Silverado I had this issue and replaced the Speed sensor and it quit doing it. Any Ideas? This problem is causing my Fiancee a lot of trouble because she is driving it every day to work and I don't want to take it to the dealership because they already pissed me off to a point that I refuse to do any business with them. Any Ideas ?

 

Call Eric Merchant at Merchant automotive, he is an expert on the Allison and very helpful on the phone.616-399-7169

 

I went ahead and just changed the fuel filter and intend on changing it again soon.
So far nothing has happened but I ma watching this truck like a hawk

 

fuel filter or fprv needs shimmed its going into engine limp mode (wont go over 2k) cause its starving for fuel