91 Speedometer Problem

Sorry if this sounds confusing but heat me out.

It seems this only occurs on really warm days or if my car sits in the sun for a long period of time.

What will happen is the speedometer will not work. And when its not working the engine sounds ALOT louder than normal. After it sits in the shade for a few hours the speedometer works again.\
Any ideas what this could be.

I have taken it to the shop that always works on my car but they have no idea what it could be.
They tell me they need it to not be working to look at it.

PPLLEEAASSEE HHHHHEEEELLLLPPPP!!!!!!!!

You Are About to benifit from My Great Wisdom-my EXACT same problem- 91 Firebird 3.1 - Speedometer on off on-

Your VSS vehicle speed sensor is not working correctly- It may or may not cause the check engine light to come on-Mine "worked" but was worn and the gear on the sensor would walk back and forth-

Engine may be 'louder' because the TCC andOD (overdrive)will not work correctly...

There are 3 different VSS on that model you must replace with the same one--

Your Welcome! :iceslolan:iceslolan:iceslolan:iceslolan:iceslolan :loser:

PS let me know WHEN this works- I screwed around with this on mine for quite a while.