I recently picked up a 98 LS 4x4. The tranny seems to not know when to shift into overdrive. It constantly shifts up and down. Also, when it is doing this, every once in a while it shutters like crazy. It feels like you are hitting rumble strips when it does it. The fluid looks good and isn't low. All the other gears shift fine. Any body got some ideas????[sm=dontgetit.gif]

 

Sounds like the TCC solenoid (torque converter clutch) has worn out the bore which the valve rides in. This will typically trigger a transmission code before getting to the point of a noticeable problem, however, if the torque converter clutch itself has worn down, it could cause the shudder.

 

Does that mean a rebuild or is this part serviceable?