Gage

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!

jgrigg

I happen to be redoing my rear end this week. I was reading the rear differential portion of a restoration book I have and it pointed out this information.

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

ratbike88

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.

the-esses

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...

jgrigg

If you do indeed have the original rear end, the codes for 72 are the following:

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

Gage

Mine says AO....of course there is no AO listed for 72...