I have a 2004 Duramax LLY that's stock except for the Super Chip programmer. When the temperature gauge is just about 185 degrees and I'm at a stop light with foot on brake the truck starts to shake. RPM is normal and does not show any engine surge. When I shift to neutral the lurching stops. When temperature gets above 185 it smoothes out. Does the same in drive and reverse. It feels like the torque converter is trying to hook up. Had the transmission serviced about 22,000 miles ago. Truck has 53,000 miles on it. Anyone have this issue?

Moved to the Allison OEM section!

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and idle surge at all in nuetral?

Does the shaking completly stop when in neutral? If not it is probably an injector.

Idle surge stops completely in neutral.

I've now changed the fluid and external filter and still have the problem. Seems the torque converter still wants to pull after the transmission downshifts to first and sitting still at idle at a traffic light. It's like you are letting the clutch in and out real fast on a manual transmission. As soon as the temperature hits the right spot it smoothes out and doesn't reappear until it goes through the heat cycle again. Has anybody experienced this?

My 06 did that and it ended up being the tranny was bad.