[tonganoxie pt]

My 2001 PT has developed a strange issue. When I drive over a divide in the road (like at a bridge) or a bit of a bump, the speedometer will drop from what ever my speed is (hwy speeeds 60-70) to about 45mph causing the cruise to increase rpm's etc etc... It doesn't matter if it's on cruise or not, same result just not as much of a surge.

I'm at about 85000 miles, have just replaced plugs and wires and this did nothing to resolve the issue.

Idle is smooth, everything seems to be in order otherwise.

Thanks for any input.