I just heard from the shop. This problem has him stumped. He said a scan revealed an 1811 code and he cannot understand why the problem returned after two weeks of running perfectly. He wants to do some research and ask a few friends what they think before he opens it up again. We need the car for work and he said it would be alright to drive in this condition. It’ a 40 minute drive one way at speeds between 40 and 55mph. Should I drive it???
What the P-1811 means is that the computer has detected that the maximum allowable shift time has been exceeded and all the shift adapts have reached their upper limits. Now the computer will max out line pressure for this code, this is why you have harsh shifting. The maximum line pressure protects your transmission. Usually after overhaul, the trans tech is supposed to clear all shift adapts with a scanner. What I would do if I were working on this is to first clear all shift adapts and check with the dealer to see if there are any software updates. If the overhaul went well and the transmission is ok, this should clear up the problem.
Thanks for your great info on this matter transman, I was worried about causing any more damage by driving it in this condition. When I picked the car up last night a GM tech was on his way over to talk to him about this problem. I wish I could have stuck around to hear what he had to say but I had an important meeting to attend. I will keep this board informed about the results and am hopping for the best (i.e. cheap) results. Many thanks again for your help and to this format for helping shed light and solving the problems of our automotive woes.