Eric76

I've been trying to find out which rear configuration my car has. I've done some research and checked the owners manual. I've found that there were two options in '76 with the Manual 4-speed.

Is there a way to find this out? A number ID stamped somewhere?
:confused:

aharte

The ratio is sometimes marked directly on the differential case. The internal gears could have been changed though.

If you have a decently calibrated speedometer and tach, you can figure it out yourself. Have a passenger write down a few values of speed vs. rpm, and then calculate the ratio from that (with one of the various online calculators for example). Use higher rpm and speeds over 20 mph or so for best accuracy.

Fevre

One way to certain is to jack the up off the rear wheels then rotate the wheel one turn counting the number of times the drive shaft rotates. 3 1/3 is 3.36, 3 1/2 is 3.55, 3 3/4 is 3.70, etc.

Mack

There is a code number, combination alpha numeric, stamped on the bottom of the differential, near the casting parting line. Read the code and either look it up in a manual or post it here. Somebody will translate.... This assumes the ratio hasn't been changed by prior owners.

doopsvette

The production code is on the bottom rear edge of the case adjacent to where it meets the cover. The differential production code begins with two letters to indicate gear ratio. This is followed by a single letter denoting assembly plant. Then come one, two or three numbers representing the day of the year the unit was assembled, after this is a single letter that indicates the source of the positraction unit (not always the same company that assembled the diff) then finally a number that represents the assembly shift that built the unit.
the differential codes: OA 3.08:1, OD 3.36:1, LR 3.36:1, OB 3.55:1,
OC 3.70:1 hope this helps dude! :cheers:


[Modified by doopsvette, 12:27 AM 10/22/2003]