Hello, I just bought an 01 GMC, 8.1 with an Allison. Truck only moves sometimes. Revving it you can hear a whirring sound, sometimes it will slam into gear then move forward and back a few times then quit. Other times it will go into limp mode and not move at all. NSBU and PSM have been replaced, Leaning towards the TC?
Allison 5sp: Allison tranny not engaging. Torque converter?
- Thread starter Danielwinn
- Start date
Sounds like the filter is sucking air or the valve body isnt sealing and sucking air.But im no trans expert. Good luck
The filter could have dropped. To start I would add some trans fluid and see if that fixes it. If it does then the filter probably dropped and you need to drop the pan and replace the filter. Get a filter lock too while your at it. Just don't drive it far with the trans over filled.
The truck was wrecked about 2 years ago. The mechanic I bought it off from did a frame swap. After the swap he discovered this issue. Like I said he replaced the NSBU and the PCM and did a flush the filter. He nor I have tested the pressures yet. Is there a pressure port somewhere near the filter on the tranny? Has anyone heard of a hard crash wrecking a torque converter? A pressure test is my next thing to do, if anyone has anything else in mind that I should test/look for please let me know. Thanks!
When you switched the trans did you reuse the old torque converter?If the problem stayed after the trans swap i dought it was in the trans,i think the problem is somewhere else.Hopfully Mike L will chime in here .
He did not separate the engine and trans when he did the frame swap. Still the original torque converter. The only codes I have seen so far are, 0700, and 0842.
Hey guys, its been a while but I finally got around to tackling this tranny. I pulled the pan and it was full of clutch material. I assume that myself and the previous owner trying to diagnose the problem is what cause the clutches to burn up. so I pulled it and had it rebuilt. I installed the rebuilt tranny with the new TC, and it wouldn't move at all. Wasn't throwing any codes just wouldn't move at all. I didn't have time to mess with it so I hauled it to the tranny shop that did the rebuild. He pulled the cooler line off and it wasn't pumping fluid. He pulled the trans back out and pulled it apart to double check his work. Didn't find anything, put it back in and fired it up and it was pumping fluid. However it now has all the same symptoms that it had when I bought the truck. It only goes into gear if you rev it and it slams in, it wont shift out of first gear, then it will go into limp mode and stop all together. It is throwing some codes now. -A- circuit low pressure and trans malfunction code. It also sometimes throws a crank sensor code and a mass air flow sensor code. I believe that the problem is something electrical outside the tranny. I would appreciate any help! thanks!