[jdl]

Are there any trouble codes? I looked at some TSBs on your vehicle, that talked about torque converter shudder, I'm not sure if that is what you have?

Happens under lite accell above 35 mph, from 3 to 4 shift or 4 to 3 shift. If the vibration happens only in first or second, or when the brakes are applied, then it is not torque converter shudder. This applies to AODE or 4R70W.

The info listed several things that might be confused with torque converter vibration. They listed axle joints--motor mounts, and the usual tune-up stuff. fuel and spark problems.

One TSB said dirty tranns fluid might cause that shudder. I'm not sure what you have going on. Good luck with that.