my friends 92 grand am with the 3.3 V6 tends to jerk at 45 mph. There is a rumble sound and sometimes it jerks but when he accelereates it does fine. we guess its a tranny problem but we're not for sure, does anyone have any ideas? soon as it hits around 45 (depends on throttle) it will kinda jerk until it gets fully into gear...once it gets past that its fine...only time it does it is going into 3rd from second. could he be loosing 3rd?

 

When it does that, depress and ride the brake pedal
a little. if the jerking goes away then returns when you release
the brake, then it is the lock up converter clutch, hunting.
( engaging and releasing repeatedly). A new lockup solenoid
may fix it. (internal)

 

It may also be an engine miss that would not be noticed when you release TCC (step on brake). Attach a vacuum gauge to the engine and go for a ride. When the problem occurs, if the gauge starts bouncing then it is an engine related problem (plugs/wires/fuel filter/etc.), if not then it is indeed a tranny problem of some sort.