I have an 88 GTA and now and then the digital speedo goes all crazy and won't give me an accurate reading. Speed readout is going all over the map +/- like 20 or so mph of what I'm actually goin.

Anyone know the reason for this?

I'm really hoping I won't have to take the dash off for this as its such a pain in the ***.

 

If you don't want to remove the dash, you can remove the VSS from the trans tailshaft housing, inspect the plastic driven gear, inspect the 'D' shaped hub of the driven gear, and check/clean the electrical connections. Make sure teh VSS spins freely. You can even meter the output coils while spinning the shaft to make sure the pulses are being generated.

Other than that, you'll probably have to remove the dash to inspect connectors.