Got this and want to get your opinions on what it is exactly. I compared the length to my other 70 gm A body vehicle and they are the same.
One revolution of the wheel turns the yoke almost 2-1/2 times.
Im thinking 71/72 2:08 or 2:56. This is a limited slip by the way.

 

Post a pic of the side of the center section. My original '71 10 bolt has two parallel ribs and a block "O" which is a dead giveaway it's a 71-72 8.5" corporate 10 bolt.

 

Look for stamped numbers, not cast, on the back side of the passenger tube, about halfway down it. Like SD or something. 2.56 was a popular highway gear. If you can get us that code, we can help.

 

Yeah been looking for a stamp but no luck but I will try some more. I thought one of you gurus would know just by looking at it. Here are some more pix.
Thx

 

it is not the same length / width as yoru 1971 72...You measured wrong.
The rear pictured is a 1973-1977 A-body rear. EVERYTHING is different except for the inner center section parts.
ring pinion carrier yoke all good to reuse.
Everything else is different. upper control arm mounts too wide, lower contril arm mounts too wide, spring perches in front not back, housing is too wide...
There are MILLIONS of those rears from 1973-1996 All the same width 62" over all / 56.25 flange to flange axle shafts are 30 5/16" long.
WE have tons of these on the shelves... Just no cars to put them in...Seems all the 73 -77 have been demo derbied around here...lol.
Grand prix, regal, cutlass, el camino, monte carlo etc...ALL gone.

JIm
J D

 

Thanks Jim,

Would the insides interchange with 71/72 (ring, pinion)?
What do you think the ratio is?

 

As stated everything is different except the inner center section parts.

So this would mean all the parts in the cast center are the same and can be interchanged.

Answer: Yes... ring, pinion, carrier, bearings, yoke, spider gears all the same as 1971 1972 10 bolt 8.5 . Corp is corp all the way to 2000

This is why they made the CORP rear to save money and make one rear to do most all cars and trucks in the most popular cars.

10 bolt 7.5 rear was the same for the smaller vehicles and low HP vehicles

RAtio
Will not be over 3.08 most likely.
2.56 2.73 most popular.
Just pull the cover it will take you 5mins and you will have the answer quick PLUS you will know if anything is worth keeping as far as condition for resale again too.

The picture gives examples of where to find the codes for ratio on GM cars from the 1964-1972 era. Once the 1973 cars with corp rears this may have changed and all went to CHEVY stamping area. Check all these area and if it is not there IT just does not exist or too rusty to see.

Jim
JD