I have a 93 Firebird Formula that was originally equipped with the 115mph speedometer instrument cluster. I got a 150mph speedometer instrument cluster that came out of another firebird. My car is an automatic and the other cluster came out of a manual tranmission car. When I hooked up the new cluster to my car the tachometer does not function properly, meaning that the needle just jumps around while I am driving and doesnt read properly. Is there some different between the tachometers from the automatic and manual, or does anyone think that the new cluster i got the tachometer is broken?