2002 Gmc Duramax

Hey everyone, I am the proud owner of a 2002 duramax 2500HD and unfortunatly I am having tranny issues, I have the allison 1000 and its having severe shifting issues, it started when I hit a pothole this last spring, it started out downshifting really hard, then it went into 3rd gear limp mode, now its acting like its in neutral when i'm in drive, i have no forward gears in 2H or 4H but can move in 4L. I have changed the NSBU switch, output speed sensor, the pressure solonoid B and the TFPS manifold. Its still giving me the p0872 code, one time it"ll say that shift valve E is stuck, then it says C circuit something. when i dropped my pan I had metal slivers on the magnet, i think my front pump is going out in my tranny and i have stuff in my valve body that needs to be cleaned, and replace my stuck E valve. Is there anything else that would make it default to neutral when i'm in drive and reverse in 2H and 4H?? I need all the advice I can get. Thank you Debbie

Welcome aboard!

The symptoms you describe is loss of pressure, either due to low fluid (sounds typical), restriction, or it simply isn't making pressure due to a fouled regulator or the pump is toast. If you're seeing a lot of metal in the pan, it came from somewhere, by some means. Being you can get it to move in low, but not high, suggests it is making some pressure, and is engaging clutches, but not enough to lock up. All the solenoid codes are likely due to this, and not likely because they have failed, other than possibly being contaminated. The TCM monitors results, so if a solenoid is commanded and the expected result isn't achieved, the solenoid is suspected and code set.

What part of the truck "hit a pothole"? The tranny cooler is right up front, and the cooler lines run up the passenger side. If it was hit or loosened, or the lines disturbed (bent, kinked, etc.), it may have started whatever led to where it is now. If the impact was significant, it may have damaged mounts, or worse.

It doesn't sound like you're getting out of this w/o an overhaul. I'd like to appear more optimistic, but I'm just not seeing it. Running and testing it any further will likely make the overhaul more costly.

I hit the front end closer to the passenger side, I never thought to check the cooler lines, thank you for that information. I know with all the metal in my pan the inside of my valve body has to seriously bogged up with stuff. I read a TSB today that said my TCM had an update or a reprogramming thing, i'm not sure how to find out about it, i took my TCM off my truck and checked the connections for loose pegs and broken wires since the harness is at such a bad angle, everything looked good, and I cleaned the connection at the back of my tranny, it wasnt bad either. I haven't climbed around under it enough to look at the rest of the harness connections. Thank you for all your help, I appreciate it very much.
Debbie

Is the ECM programming turned up significantly?

Metal slivers on the magnet definitely not a good sign. Light weight black fluff is plenty normal though. Sounds like something is coming unraveled and is contaminating the valve body causing valves to stick. We don't see many issues with these transmissions unless abused. It is possible that a torrington bearing has failed though I guess.