Slow response and vibration (separate from response)

krunning

Background-two separate symptoms: 1) My Denali has about 32K miles on it and IMO it has always had a slow response followed by jerking acceleration. When I took the car into the dealership for an unrelated issue, the service manager, who was riding with me to diagnose the unrelated issue, told me that the jerking was because the car was getting used to how I drive and once it knows my driving style the jerking will stop. He was right to a certain extent. However, the car still is slow to respond, especially when starting from a stop. 2) About a week ago I noticed an intermittent vibrating periodically on the right side of the vehicle. A lot like when driving over those "wake up" strips before coming to a stop sign or when you drift too far off the road. There was also slight vibration in the steering wheel. I didn't think too much of it until I took a drive along a long, relatively even, road. During the drive, the vibrating became cyclic, occurring after one full rotation of the tires (or close to it) for about 20 miles. I then hit a very strong thunderstorm for about 25 miles and when I got to my destination the symptoms stopped completely and didn't start again for 36 hours. Now the symptoms are intermittent with no associated patterns that I can identify. I would like experienced opinions before taking it to the dealership...is my transmission slipping? thanks in advance, Kim.

krunning

Update: Took the vehicle to the local GMC dealer and the service manager went on a quick ride with me. He diagnosed the problem immediately. Apparently GM just issued a service bulletin on the torque converter...glad the mystery is solved!

Mr_Shiftright

So what did they do? An ECM update? Torque converter issues vs. a "misfire" are sometimes very tricky to tell apart, even for the professional mechanic.