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Tachometer is showing 4000 + at normal 55mph driving! whats wrong?

Is the motor actually revving at 4k rpm? Or is it at the rpm it should be in O/D? That's the first question. If it is at normal rpm and showing the wrong rpm, a gauge cluster motor could have gone kaput. It's becoming more prevalent as our cars get older, although it is seen more on GM trucks than anything else.

The engine is normal its the tach that is showing a higher than actual RPM.

I would suspect you need a new cluster, I believe harofreak00 has one for sale.

Otherwise you can have the stepper motor replaced by someone experienced with that. I do think that it's in the cluster, though.

My theory is, if one is going, the others may follow suit soon after, cheap insurance to replace the whole thing. IMO

Thanks for the info regarding my Tachometer. I need to get it fixed, is it difficult for a mechanically inclined person to fix it?

It's not bad if you're a patient, careful, mechanically inclined person. My oil pressure, temperature, and voltage gauges would get stuck, not move at all, or peg until I replaced the stepper motors. There are a few good youtube videos that show how to do it in other gm vehicles. You really need a solder sucker to remove the old ones and be very careful with the heat. I think I popped a light when I took my cluster out so replacing them all is the next chore.