Diff prod code, where is it?
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 923
Likes: 4
From: Austin Tx
Diff prod code, where is it?
I found the date code, and the casting #, but where is the code that tells you what ratio you have? Car is up on the rack and I am looking everywhere with the flashlight but can't find it. feels like I have 3.55 or 3.70 but can't tell for sure.
thanks!
thanks!
Instructor
Joined: Feb 2006
Posts: 200
Likes: 0
From: Whitmore Lake MI
Ratio code answer
I looked for this on mine just a few days ago.
It's on the bottom of the front case just in front of the rear cover. Mine were very faint, but I did find them with some degreaser and a brass wired cleaning brush. You May have to clean the bottom really well because my letters were very shallow. If you've painted the rear dif, good luck!
Mine was OM which is a 3.36 : 1 ratio for a 78. If you can tell me the year and the code, I could look up the code in my book for ya. Or better yet, I'll try to post it for ya.. Unfortunately it wouldn't be until monday.
Hope this helps.
Jeff
Intermediate
Joined: Jan 2006
Posts: 40
Likes: 0
From: Colorado Springs Colorado
Diff Codes
The codes on the rearend will tell you the gear ratio that was originally installed, but it is possible the gears have been swapped out one or more times. One way to determine your actual gear ratio is to jack up the rear of your car and put a chalk mark on the inside of your tire and a chalk mark on your driveshaft. Rotate your tire 1 complete revolution while counting the number of driveshaft rotations. 3 1/2 driveshaft revolutions to 1 tire rotation is approximately 3.55, for example.
Intermediate
Joined: Nov 2004
Posts: 28
Likes: 0
From: LHR UK
Very shallow, scraped plenty of crud off to find mine and then I could only see it in the right light, it's located on the bottom edge where the case meets the cover, I rubbed a bit of chalk over it so I could read it a bit better, here's some pics...
Last edited by the-esses; Jan 13, 2007 at 12:33 PM.
Instructor
Joined: Feb 2006
Posts: 200
Likes: 0
From: Whitmore Lake MI
72 Codes
All are Posi.
3.55 AA
3.70 AB
4.11 AC
3.08 AW
3.36 AX or LR
2.73 AV
Hope this helps you.
Jeff
