Topic: RPM?
in Forum: C3 General Discussion
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West Bend, WI - USA
Joined: 3/18/2010
Posts: 46
Vette(s): 1985 silver coupe & 1975 red coupe
I recently bought a 1981 Vette that is all stock. It has an automatic transmission and at 70mph the thing tachs 3000rpm. Does that sound about right? I would have thought with a 2:87 gear in back my rpm's would be lower than that assuming the tach is reading correct. What do you guys think. Thanks much, Darrell
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20229
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Assuming that you actually still have the 2:87 gears, it is high. With 3:36 gears in my '74, 3000rpms is just over 75mph. Your gears may have been swapped somewhere down the line, from the looks of it. It could be a problem with the tack, but I would lean more towards the gears having been changed.
Joel Adams
C3VR Lifetime Member #56 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Lifetime MemberLemon Grove, CA - USA
Joined: 10/17/2007
Posts: 2041
Vette(s): 1982 C3 Collectors Edition 44000 miles, sat in the sun most of its life, My wife purchased it for me for Father's Day in 2007 from her girlfriend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.
How sure are you of your speed? Change your wheel size a little or just stock and your Speedo could be 10% off easy. I checked mine with my Gramin and found that it was 10% off had to change the speed gears on the transmission.
You might want to confirm your speed before you get going to far. Of course you can do that on a lot of California highways with the mile markers they have set up for that purpose.
in Forum: C3 General Discussion
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