quick question here for all you friendly people out there

what sort of revs are you showing at 50 and 70 in o/d

trying to get a rough idea a what rear-end I may have in mine since the revs and speed do not seem to tie up with what should be a 2.73

 

If what you're really trying to accomplish is to figure out what gear you have, skip all the guess work, and go directly to the reality.

Have you changed your rear end fluid lately? If not, then you need to; and you have to take off the cover to do it. While you're there, make a point of looking at the gear; the ratio is stamped on the edge of the ring.

The factory tachs in these cars are notorious for being inaccurate. Usually they fail by reading too high. In fact, I have never had one that was accurate; the one in my car now is the closest one of any I've ever had, and it's only about 300 RPM high at 6000 (5% error). That thing in your dash is regarded by GM not as an "instrument", but rather a "trim package". Check it against an actual instrument of known accuracy such as an ignition analyzer or something; I'd be surprised if it was anywhere near accurate.

 

Mines actually about 300rpms off. I know because when we had a diagnostic computer hooked to the ADL and the TPS sensor we could see a rock solid 750rpms and the tach would show anything between 700 and 1100. It would fluctuate slowly.

 

1500 RPM @ 50mph
2250 RPM @ 70mph
3:42 rearend.