89 NewYorker ... if not the tranny, then what can it be??

[neinfrared]

I am at loss on what the problem can be.

While driving, my speedometer suddenly starts to go crazy and then maxes out. As soon as it does, my car starts to buck (like when a fuel filter is clogged and the car wont go) and I need to take my foot off the pedal and hope it calms down before I step on it again.

It has happened on the road and on the highway.

I have taken it in to the tranny guys who replaced the fluid and filter. They say the tranny looks very good. Nothing that sticks out as being in need of a fix.

Anyone have this problem or knew of someone who did and what the fix is ??

Thanks

John