I recently bought a 2007 uplander, mainly because the body was in good shape, and it was clean. During the road test, there was an occasional clunk at low speeds, but I thought it was maybe a worn engine mount, so I bought it. After driving it home, I remembered similar transmission problems with a 2004 Uplander that I had owned before. This is the 4 speed auto, and has a 3.9 litre engine. At full throttle transmission it shifts perfectly, at around 5500 or 6000 rpm each time. However, after stopping, it will clunk, grind, or shudder, when starting to roll again, almost like it is not sure which gear it is in. Usually, just accelerating very slowly will get it moving okay. So, I am hoping this is a problem with the relays, that can be fixed without taking the whole transmission apart. It is not slipping, like a worn transmission. I know what that feels like. Does anyone have a patch for this problem? Like maybe a reworked, or reprogrammed set of relays? Has GM admitted they know about the problem and issued a recall? The engine light doesn't stay on, but shows up occasionally. I didn't bother to see if there were any pending codes. I see you told someone else to try some lucas additive, so I could definitely give that a try. This was a one-owner van, and the owner said he had never replaced the trans fluid, when I asked.

My 2004, which had a 4 cylinder engine, but also a 4 speed auto trans, used to stay in a high gear when the van stopped, so there was no power when you tried to move again. I found that I could just shift to first gear, and it would work okay, but what good is an auto trans that you have to shift manually?