i have a SA rear end out of a 72 cutlass. i know that it is an open rear end but are all the 72 rear ends in the A body an 8-1/2 inch? how do i tell if it is?

i am just full of questions lately, sorry.

 

An 8.5 has a 10 bolt cover, and 10 bolts on the ring gear.
a Type O has a 12 bolt cover, with 10 bolts on the ring gear.

 

8.5 has a squareish nub on both sides of center section bottom , 8.2 will have pointy ***** on both sides of center section bottom.

 

There were 2 different castings for the 8.5" 10-bolt,for the 71-72 Cutlass/442,so you can't always look for the nubs or lugs,as some call them.The is the casting with a large "O" on each side,facing the front,of the pumpkin,where the tube presses in.This casting will also have the round cover,with a protruding rib that runs from 12:00 to 3:00.
The second casting has a large "A" on the top,& on the sides of the pumpkin,where the tubes press in.This casting will have a cover with notches at 9:00 and 3:00,& the cover looks just like an early BOP 8.2" cover,bolt the bolt spacing is different.

ALL of the 71-72 Cutlass/442 & ALL of the 71-72 Skylark/GS cars came with an 8.5" 10-bolt from the factory.

 

Does anyone have a pic of the "o"s and "A"s on the housing?

 

Of course, the Type O also has an 8.5" ring gear...

 

Another 72 diff question if I may..
Mine has a 10 bolt, non-limited slip with a W27 cover on it. I believe its just the stock item of the day.
I jacked it up yesterday looking for a noise which turns out to be a front wheel bearing, but I notice the rear passenger side axle has in/out movement of approx 1/4" as against the drivers side <1/16".
No bearing noise etc but I'm thinking that amount of movement is too much.
Thoughts & what is the normal cause? I know zip about diffs.

 

Are you guessing on the measurement or did you take a dial indicator reading ? 1/4 is TOO much.

So get an accurate measurement before totally freaking out SOME movement for a used bearing is acceptable .005-.030 BUT .250 is way out of wack.

CAuses- you could have the wrong axle seal in the housing which on the 1969 70 71 72 rears is what keeps the end play in check.

another reason could be a bearing on its way out fast. one good chuck hole or curb bang could take it out.

Best yto yank the axles and inspect after you take the measurement with the drum and tire off the car. attach the indicator to the backing plate and make the plunger ride straight into the axle machined surface parallel with the in out movement so you get a true reading.

Pictures below are your 'O' 10 bolt 8.5 with round cover and your 'A' Buick 10 bolt 8.5 with the scalloped cover. BOTH 8.5 and all 8.5 rears come with 2 steel straps and 4 bolt 2 for each strap- u-joint retention as pictured.
U-bolts were 10 bolt 8.2 bop and 12 bolt olds u-joint retention

OLds 12 bolt ring gear diameter is 8.4 not 8.5.

Hope this will clear up 8.5 1971 1972 rears.

All 12 bolt and 8.5 rears take 2.25 quarts to fill (dry) BUT you should ALWAYS fill to the fill plug back flow dribbles on a flat level surface. That also does not account for 4-8 oz. of limited slip additive.

1 gallon is the reason you were having fluid spit from the vent tube and surprised you did not blow the seals out too. ??? NOW the only way I can figure that much oil was was able to be put into the housing through the fill plug was HIGH pressure or you said you had a T/A cover and they filled it to the T/A cover fill plug WHICH IS TOO HIGH to use as a fill level point. The GM fill plug on the passenger side above the cast support webbing is the correct fill level guide. PERIOD. lol

Good luck, Jim
J D Race