Determining Rear Diff Ratio???
Thread Starter
"Rodstoration &am p;quot; In Progres
Joined: Jun 2004
Posts: 1,397
Likes: 1
From: Frisco TX
Determining Rear Diff Ratio???
How can I determine the rear ratio of my 80 without pulling the cover and counting teeth? I have done the "turn the wheel and count the revolutions on the drive shaft" process and think it's a 3.08... but want to be certain.
Thanks again in advance...
Thanks again in advance...
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 88
From: State of Confusion
"certain" ?
Pull it apart.....
'Counting-the-revolutions' is a fairly-accurate means of determining ratios;
if you want to be REALLY PRECISE, spin the drive-shaft until the tire does 10 revolutions (30.8 drive-shaft revolutions, or almost 31), or.....
lay-out 10 even increments around the driveshaft (diameter x 3.1416 div/by 10) with chalk, and count (again, 3.08s would be 3 complete revolutions, and almost to the 1st mark).
I have one source-book stating that '80 stick-cars came with 3.08s, and automatics came with 3.55s, but I'm not sure it is 100% accurate...
Pull it apart.....
'Counting-the-revolutions' is a fairly-accurate means of determining ratios;
if you want to be REALLY PRECISE, spin the drive-shaft until the tire does 10 revolutions (30.8 drive-shaft revolutions, or almost 31), or.....
lay-out 10 even increments around the driveshaft (diameter x 3.1416 div/by 10) with chalk, and count (again, 3.08s would be 3 complete revolutions, and almost to the 1st mark).
I have one source-book stating that '80 stick-cars came with 3.08s, and automatics came with 3.55s, but I'm not sure it is 100% accurate...
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Originally Posted by Glensgages
"certain" ?
'Counting-the-revolutions' is a fairly-accurate means of determining ratios;
'Counting-the-revolutions' is a fairly-accurate means of determining ratios;
Race Director
Joined: Jan 2003
Posts: 15,176
Likes: 88
From: State of Confusion
Originally Posted by mandm1200
I have the rear out and was curious of the ratio. I spun the side yoke and also counted the number of times the pinion shaft went around. Took a couple of times as it gets confusing keeping track to the numbers. Came out to be 18.5 / 6 or 3.08.
is that how your '76 originally came equipped?
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Originally Posted by Glensgages
That same source-book says that 1976 L-48/automatics came with 3.08s;
is that how your '76 originally came equipped?
is that how your '76 originally came equipped?
Mike
Safety Car
Joined: Feb 2000
Posts: 4,977
Likes: 38
From: Massachusetts , USA,
Originally Posted by 80TexasC3
How can I determine the rear ratio of my 80 without pulling the cover and counting teeth? I have done the "turn the wheel and count the revolutions on the drive shaft" process and think it's a 3.08... but want to be certain.
Thanks again in advance...
Thanks again in advance...
Intermediate
Joined: Jul 2004
Posts: 30
Likes: 0
I ask this question before to another die-hard Vetter and this is what he emailed back to me.....
Rob,
One way is to jack the car up and set the pinion (drive shaft differential flange) vertically and mark the side thats down.* Rotate a rear tire one full turn and count the rotations of the pinion.* Chances are it is a 3.08, a 3.36 or a 3.55.
Another way is to look at the bottom of the case just in front of the back cover.* The codes will read either
AW (3.08)
AX (3.36)
AA (3.55)
AB (3.70)
There are other codes possible, but these are the most common.
Alan
Hope this helps......
Rob
Rob,
One way is to jack the car up and set the pinion (drive shaft differential flange) vertically and mark the side thats down.* Rotate a rear tire one full turn and count the rotations of the pinion.* Chances are it is a 3.08, a 3.36 or a 3.55.
Another way is to look at the bottom of the case just in front of the back cover.* The codes will read either
AW (3.08)
AX (3.36)
AA (3.55)
AB (3.70)
There are other codes possible, but these are the most common.
Alan
Hope this helps......
Rob
