82' Drive & Driven Speedometer Gear Issue
Thread Starter
Intermediate
Joined: Sep 2012
Posts: 38
Likes: 0
From: Opelousas Louisiana
82' Drive & Driven Speedometer Gear Issue
Just had 3.73 rear diff installed and of course the speedo is way off now. So I crawled under the vette and found yellow drive gear (19T) and yellow driven gear (41T) if charts for 700R4 are correct. Back calculate that with 26.8" tires and presto gears for 2.87 rear diff which should be the original stock size.
OK so problem is I don't plan on doing any tranny work soon so the yellow 19T drive gear stays put. That leaves either finding a 53 tooth driven gear, which I have yet to find, or go with a digital speedo that can be calibrated. Just wanting reasonable speed accuracy.
Looking for any suggestions on how to fix this mechanically, or recommendations on digital gauges. If I go digital I will probably just do the entire dash cluster that way.
Side note for those who are novice like me. I dropped the rear and center bolts to the exhaust because the speedo cable goes into the tranny right at the cross member. Used an adjustable wrench to loosen the speedo cable. Used a 10mm socket with semi flexable extensions to remove the retaining bolt. Then used the adjustable wrench to pull out the housing of the driven gear.
OK so problem is I don't plan on doing any tranny work soon so the yellow 19T drive gear stays put. That leaves either finding a 53 tooth driven gear, which I have yet to find, or go with a digital speedo that can be calibrated. Just wanting reasonable speed accuracy.
Looking for any suggestions on how to fix this mechanically, or recommendations on digital gauges. If I go digital I will probably just do the entire dash cluster that way.
Side note for those who are novice like me. I dropped the rear and center bolts to the exhaust because the speedo cable goes into the tranny right at the cross member. Used an adjustable wrench to loosen the speedo cable. Used a 10mm socket with semi flexable extensions to remove the retaining bolt. Then used the adjustable wrench to pull out the housing of the driven gear.
Burning Brakes
Joined: Mar 2010
Posts: 943
Likes: 15
From: Valdosta Georgia
I went to this site: http://transmissioncenter.net/speedo...__va.htm#700r4
I don't think there is such an animal as the 53 tooth driven gear. You will need a 15 tooth drive gear (gray) and a 42 tooth driven gear (green) with 27" tires for a 3.73 rear.
They have speedos now that use GPS to calculate speed. That might be an option, then your speedo is not tied to your transmission at all.
I don't think there is such an animal as the 53 tooth driven gear. You will need a 15 tooth drive gear (gray) and a 42 tooth driven gear (green) with 27" tires for a 3.73 rear.
They have speedos now that use GPS to calculate speed. That might be an option, then your speedo is not tied to your transmission at all.
Last edited by Drawmain; Aug 9, 2014 at 11:41 PM.
Instructor
Joined: Jul 2007
Posts: 130
Likes: 3
From: Goshen IN
I got my ratio adapter for my 82 from this web site when I changed to a 3.55 rear end. I went to the largest driven gear I could get, but was still 10% fast, so I got the 10% ratio adapter. I'm only 2mph fast at 60mph. They have a number of different ratio adapters. Its tight working putting it in, but is doable. I took the preformed radius metal off the cable so I could route it better. Its not an inexpensive adapter($62).
