Speedo calibration
Thread Starter
Instructor
Joined: Mar 2003
Posts: 235
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Speedo calibration
Does anyone know what speedometer gears to use with 3.73 gears a T-350 tranny and 255/60R15 tires (27in tall)(778 revs per mile). This is all in a 1980 corvette. I would appreciate any help you could provide me with. Thank you.
[Modified by IRON WILL, 12:17 PM 4/21/2003]
[Modified by IRON WILL, 12:18 PM 4/21/2003]
[Modified by IRON WILL, 12:17 PM 4/21/2003]
[Modified by IRON WILL, 12:18 PM 4/21/2003]
Burning Brakes
Joined: Apr 2003
Posts: 844
Likes: 0
From: Central KY
Re: Speedo calibration (IRON WILL)
Iron Will,
I'm a long way from home, but I remember calibrating my speedo last year. I pulled out my factory service manual (and other reference books whose titles now escape me...I have tons of great corvette books) and figured what engine rpm I should get at 60 mph with stock tires. I think I had 2500 at 60 mph for 3.31:1 stock gears (my car). I then bought all speedo gears from 18 to 22 teeth and tried them until I got that reading. Someone had put a gear reducer in my speedo cable (probably to alleviate a cable breaking problem), but the factory did not use this for the stock 3.31 gears. They did use one for 3.73's. My speedo had been reading low (indicated 65 was well over 70 by friends pacing me), but this trick solved the problem. Sorry I can't get the details for you over here, but you get the idea.
Good luck!
I'm a long way from home, but I remember calibrating my speedo last year. I pulled out my factory service manual (and other reference books whose titles now escape me...I have tons of great corvette books) and figured what engine rpm I should get at 60 mph with stock tires. I think I had 2500 at 60 mph for 3.31:1 stock gears (my car). I then bought all speedo gears from 18 to 22 teeth and tried them until I got that reading. Someone had put a gear reducer in my speedo cable (probably to alleviate a cable breaking problem), but the factory did not use this for the stock 3.31 gears. They did use one for 3.73's. My speedo had been reading low (indicated 65 was well over 70 by friends pacing me), but this trick solved the problem. Sorry I can't get the details for you over here, but you get the idea.
Good luck!
Burning Brakes
Joined: Apr 2003
Posts: 844
Likes: 0
From: Central KY
Re: Speedo calibration (djcwardog)
I went to the follwing site to get the factory specs for a 1973. This should work for you as well. Find the gear ratio and go from there... Good luck!
http://www.corvetteforum.net/c3/vette73/S_SPEED.htm
http://www.corvetteforum.net/c3/vette73/S_SPEED.htm
