I don't know if I have a problem or not.
When I am cruising on the Xway at 75, my tach is reading only 2K. That seems low even though I have a 4-speed auto and 2.87 rear end.
Are there charts or specs for MPH vs RPM?
She idles at 800 to 1000 when warmed up.
The tach seems normal, just low.
What do you think?

At 75 on my 75, the tach reads around 3500 rpm. All factory. I would say that you needed to have your tach checked.

Hook up another tach and do a comparison at different RPMs. That will tell you. You can do this in the drive way, you don't have to drive it.

Hi, just incase you want a "formula" to determine your RPM at a corrisponding MPH, or vice-versa, you can try this , just fill in the blanks, and click on Calculate...

This one is for RPM's at a given MPH, you will need to know your tire's diameter, the rear gear(which you already said was 2.87) and the drive gear ratio(which in 4th gear will be 1 to 1)..

http://www.race-cars.net/calculators/rpm_calculator.html

This is for MPH for a given RPM (it is basically the same formula, just re-arranged)....

http://www.race-cars.net/calculators/mph_calculator.html

These are real helpful when trying to choose a rear gear for "cruising"...

Hi,
My 82 has a 2.87 rear axle ratio and the four speed overdrive automatic. Your tach readings don't surprise me, they seem about the same as my car's tach readings.
Hope this helps,
Tom

Guys,
Thanks for the feedback. If my neighbor has a good spare tach, I'll try hooking it up.
I knew the formula for converting MPH to RPM, just don't know what 4th gear ratio is. I think '82s have overdrive, but not sure.
Anyone else with a stock '82 have comparable numbers?
I know I get 20+ MPG.

I think your overdrive gear is around .70
Tire diameter is around 26" I believe. Are you running P255/60R15 tires?
I have to do a little research later if you don't get a definite answer.
Sarge

Sarge81,
It wouldn't have been my choice, but the tires that came with the vette are P225/70R15. They measure 27.5" in diameter.
Using the calculator that stingrayjim recommended and .75 for the overdrive, 75 mph = 1974 rpm. So I guess my tach is OK.

That 350 engine hardly ever works.

Hi Dwright,
My 82 is stock and is geared so high I use the "3" setting on the auto trans around town. I only use "D" if I go on the highway. Our cars were built during the dark days of gas crisis and the engineers were more concerned with fuel economy rather than performance. I have seen some posts where guys have swapped out the rear axle gears for a lower ratio. Seems like the results are pretty good and drivabiltiy is improved.
Your Vette is sharp looking.
Enjoy,
Tom

Good suggestion on third gear around town.
I hate it when the tranny is searching back and forth around 40mph. Real clunky.
And when you lightly accelerate it's loaggy (is that a word?), especially going up a slight grade. Not to mention the pinging if I get bad fuel.
Thanks for the props on the vette.