speedometer off
Thread Starter
Instructor
Joined: Nov 2012
Posts: 209
Likes: 7
speedometer off
When i bought my 76 vet, the previous owner told me that because he had installed 3.90 rear end gears that my speedometer would be off a bit. Its about 12 mph off, which i can actually live with. He told me that i'd need to change out a couple gears in the transmission to balance this problem. Where would i buy these gears and what would i be looking for?
I'm in the process of removing my motor from the car so i thought i'd ask about this, maybe its something i could fix while i'm at it. But maybe it's way more work than what its worth?
Thanks
I'm in the process of removing my motor from the car so i thought i'd ask about this, maybe its something i could fix while i'm at it. But maybe it's way more work than what its worth?
Thanks
Last edited by greghennings; Nov 24, 2012 at 09:04 PM. Reason: had put down 3.80 instead of 3.90
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Well. If he changed it to a 3:90 he really did something special. No such animal.
I am assuming its reading fast. All you have to do is slow it down by changing the speedo drive gear at the transmission. Probably about two teeth more than you currently have. Pull the gear and count teeth.
I am assuming its reading fast. All you have to do is slow it down by changing the speedo drive gear at the transmission. Probably about two teeth more than you currently have. Pull the gear and count teeth.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
automatic or manual?
It would take a speedo drive gear (inside the rear of the trans (follow the speedo cable) with 3 more teeth....IF the gear on the tranny output shaft will allow that many teeth. Most parts places sell [or can get] speedo cable drive gears. But, you will need to know the exact gear ratio of the differential and your rear tire size.
It would take a speedo drive gear (inside the rear of the trans (follow the speedo cable) with 3 more teeth....IF the gear on the tranny output shaft will allow that many teeth. Most parts places sell [or can get] speedo cable drive gears. But, you will need to know the exact gear ratio of the differential and your rear tire size.
Last edited by 7T1vette; Nov 24, 2012 at 10:21 PM.
Le Mans Master
Joined: Aug 2010
Posts: 5,339
Likes: 546
From: Central Texas
This page has a wealth of information. The part numbers are GM. You may be able to get some of these through a local dealer. If not the Corvette vendors or transmission rebuilders usually have them.
http://chevelleengineer.home.comcast...eer/speedo.htm
http://chevelleengineer.home.comcast...eer/speedo.htm
Thread Starter
Instructor
Joined: Nov 2012
Posts: 209
Likes: 7
hey thanks guys, i'm dealing with an automatic trans, i'll take a closer look here in the next couple days. Easy fix that i just thought of, I could keep my GPS in the car, its got a speedometer on it. I'm the only one that'll be driving it anyway...but it is nice when everything works properly.
