My friend’s 1970 GS350 has this rear axle. He thinks it’s an original 8.2 because of the scallops on each side of the cover but I think it’s an 8.5 with an 8.2 cover because of the “ears” at the bottom left and right of the case itself. So, which is it? The guy who’s wrong buy the beer.
Again cover is irrelevant. That cover can work on any 10 bolt, but generally from the factory it was a 8.2. Your friend has a 8.5 with a 8.2 cover.
Back up the bus for a minute with the covers. The 8.5” 10-bolt has a cover that looks like the BOP 8.2” cover,but they are different. The bolt spacing is different. The 8.5” cover has a bulge at the lip,around the 12:00 and 6:00 bolt. The 8.2” cover has a notch for the brake hose bracket. The 8.2” BOP cover is at the top. One of the 8.5” 10-bolt covers is on the lower right. Similar but different. Now,the cover on the lower left is also an 8.5” 10-bolt cover. This cover came on a different casting and came under ALL 71-72 Cutlass/442’s that were built in Lansing Michigan. It’s the same 8.5” 10-bolt with the same guts. However,that casting has fangs at the bottom,not the big square lugs. The cover on the lower left will fit ALL 8.5” 10-bolt castings and also 8.2” Chevy,as they all have the same bolt pattern. However,the cover on the lower right will not fit the other castings due to oiling holes being exposed where the notches are.
Regarding axles on the Buick 8.5, were they all 28 spline or were any produced with 30 spline axles? And were they C-clip or not?
All of the 8.5’s were 28-spline until 1988,then they all went to 30 spline. The BOP cars had bolt-in axle 8.5’s until the mid/late 70’s. They everything went c-clip. A posi unit that is machined for c-clips will work for both,but a posi unit from a bolt-in axle rear does not have the side gears machined for c-clips and thus would not work in a clip rear. Any new posi unit that you buy today will work for both.
Easy way to tell a 8.2 from a 8.5 rear is the 8.5 has a Brake hose retaining boss at the top of the casting. NO 8.2 chevy or pontiac or buick 8.2 ever had that. ONLY 8.5 CORP. Reason why Brians cover picture there is a slot in the 8.2 cover for the 'L' bracket that holds the rubber brake line. Just feel the top of the casting in between the control arm ears you will feel a boss and it will be tapped for a 5 / 16" bolt same thread as the rear cover bolt... UNDENIABLE way to tell. even covers can be modified and switched. Even the stealthy Olds 8.5 switch does not have the lower 5 and 7 o'clock triangle castings. Look at the picture (GREEN ARROWS)
These are all 8.5” housings. Note the tapped boss on top,as Jim mentioned. You will also see some differences between the “A” casting and the “O” casting. You will see the additional oiling holes at 9:00 and 3:00 on the “O” casting and also see the teeth or fangs at the bottom. The take the same internals,shafts,yoke,etc.
Great info here. One more Q? Where did the factory place the posi tag? I've seen it all over the place on different rears.
All the ones I have seen were 5 o'clock ....BUT you know how that goes....The assemblers could have put it anywhere really if they wanted too. Normally it was low enough for the maintenance guy to tell it needed special fluid for oil change etc. I have seen them upside down with boss stamping facing down - hanging out past the cover edge parallel with the ground flagging towards the passenger side .... Which is the way I put them on when i redo a rear. readable from the rear of the carleft to right reading.
Speaking of the oil holes, my 1997 GMC 8.5 had a gasket from the factory WITHOUT the oil holes.....it blocked the holes. I put one on with the holes.... Was that a factory error???
They started making slots in the casting for the oil to go around the carrier bearings. Do not sweat it.
