what gear do i have
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 42
Likes: 0
Well, there ya go, according to your "dead on" speedometer, you have the ultra-rare 2.91 rearend ratio. Maybe your tach is not 100% accurate. Maybe your speedo is inaccurate. Maybe your clutch is slipping just a teeny-weeny bit. Maybe there is a loose nut behind the steering wheel. The only way to REALLY know, is to take the cover off and count the teeth. That's a pretty big job on a 'vette, so counting the driveshaft revolutions is the next best thing.
Scott
Scott
Thanks, John
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Scott
Race Director
Joined: Aug 2004
Posts: 10,628
Likes: 132
From: Duvall, WA
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Where this post went off the rails is by involving tire sizes and accuracy of actual road speed.
Put shopping cart wheels on it and take it for a spin- it will still read 80mph @3000 rpm.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Not in the least. There's a fairly large jump in RPM between each possible ratio so even if both gauges are slightly inaccurate the answer can easily be given.
Where this post went off the rails is by involving tire sizes and accuracy of actual road speed.
Put shopping cart wheels on it and take it for a spin- it will still read 80mph @3000 rpm.
Where this post went off the rails is by involving tire sizes and accuracy of actual road speed.
Put shopping cart wheels on it and take it for a spin- it will still read 80mph @3000 rpm.
Ehhhh, I guess you have a point there. Personally, I'd rather pump a jackhandle a few times than wrap my head around the math required to figure it out. Tougher on the arm muscles, but easier on the head muscles!!!
Although, I imagine there are online calculators for this sort of thing, aren't there? Maybe I can give the old arm muscles a rest, eh?
Scott
Burning Brakes
Joined: Jan 2006
Posts: 1,223
Likes: 174
From: Fort Wayne IN
In 1973 we were well into emission controls .....and dealer inventory ordered cars would be the standard ratios as performance was already history....With 'OEM size tires a tach reading of 3000 RPM reads 60 MPH on the odometer and would be a 4.1 gear....which was not available in 73
Le Mans Master
Joined: Dec 2007
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From: McHenry Illinois
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Redoing the calcs with the actual tire size indicates either a tach error of 173 RPM low, or a speedo error of almost 5 mph fast, the latter being more likely.
Most speedos indicate ~5 mph fast.
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Drifting
Joined: Jan 2011
Posts: 1,853
Likes: 81
From: Hamilton Virginia
Well according to the chart , with me running about 60mph and the tach reading about 3,100 rpms, That would mean I have 4:10 gears.
