Speedometer swings on rough roads

[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.

[bobs turbo pt]

if i read this right you are loosing power ?? is your speed going down to 45 ?? i would check the transmission fluid or something wrong in the transmission [:I]

[tonganoxie pt]

no power loss, or loss of speed, just the speedo goes from 60 to 45.

[quicksilverdon]

Just a hunch, but the speed sensor could be going or wiring to it is flaky.
Not sure where it's located - maybe buy a Chilton's or Haynes manual.
The fact that cruise acts up means it isn't the speedometer but the signal feeding the speedometer (and cruise).

[tonganoxie pt]

Thanks a bunch, I'll check it out and let you know the results.

[bobs turbo pt]

good luck !! [8)]