Where exactly can I find the gear ratio number on a 72 differential? Can it be seen while installed? Found what appeared to be the assembly date stamped on bottom next to cover.
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The numbers/letters stamped on the bottom have to be "DE-CODED" using a chart. Provide the info, and someone might be kind enough to look it up for you and tell you what your diff is SUPPOSED to be. There's no guarantee that the internal parts still match the external code on a 27+ year old car. You can mark the drive shaft and the half-shafts with chalk or tape, and count how many times the driveshaft turns for one half-shaft revolution. Divide it out, and you have the ratio. -
Re: gear ratio
Tom gives you good advice. First there's the question of what was in the pumpkin from the factory, then there's the issue of what's in it now and whether the tranny/speedo has been changed to match. So, knowing what was there originally can be a moot point....
The case is just that, a case. It says when it was built (as you've noted and Tom confirms), but the 'case' had no idea what ring/pinon was going to be stuffed inside so you won't find that info.... On the top (where rear spring mounts), the factory slapped a paper tag down with a 2-digit broadcast code of what was inside and this matched the order sheet for gear ratio (FA, CB, Etc.).
But, you gotta drop the entire pumpkin to access this and odds are good it's turned to dust by now! So, what it was may well be less important that what it is and Tom tells you how to check by rotating the rear wheels, counting revs, and watching the drive shaft turn....Comment
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