I'm trying to track down a (apparently very rare) Gm 8.5" 10 bolt housing that fits a 68-72 GM A-Body .... (see attached picture) I've seen these axles turn up a few times as for sale.. but I cant' find any information on what they might be... every thing i've looked at shows an 8.5" 10 bolt as a completely round cover. .(no scallops in the sides)...
I've already purchased a brand new 30 spline eaton posi, matching 30 spline moser axles, 3.73 gear set, 1350 series forged pinion yoke.. install kit.. so I'm kinda committed to an 8.5" 10 bolt ... having no idea a housing was going to be this hard to find
never mind.. found the magic combination of google search key words.. the scalloped covers are B.O.P axles...
You can identify the B-O-P assemblies by the two reverse-scalloped sections of the differential cover located at the nine and three o'clock positions. B-O-P axles also have identifying grooves traveling along each side of the differential housing. The Buick 8.2-inch rears have a single rib that runs down the side of the housing horizontally, while the Pontiac axles have a second converging rib. Internally, both the Buick and Pontiac 8.2-inch axles use a 1.438-inch 27-spline pinion shaft and 28-spline axles. The Chevrolet and corporate axles do not have the side ribs and use a different cover with a lube "gutter" stamped in. Additionally, the GM corporate 10-bolt, which used an 8.5-inch ring gear, also has two angular projections in its casting, radiating from the differential housing around the five and seven o'clock positions.
Nope, the '71 and '72 GM A body 8.5 also has the scalloped cover. This is the only 8.5 10 bolt that had bolt in axles instead of c clip axles. They were used in '71 and '72 Cutlass and Skylarks. Everything inside is exactly the same as all other corporate 8.5 rear ends except the way that the axles are retained.
Exactly. The A body 8.5 has bolt in axles. Don't misunderstand me, I don't mean that the BOP 8.2 is the same thing. They are completely different rear ends. As far as I know the '71 and '72 Cutlass and Skylark were the only A body cars to get the corporate 8.5 rear end and these early 8.5 rear ends did not have c clip axles. They also did not have the round cover. The F body and other GM cars also got the 8.5 in '71, but for some reason they had c clip axles and the round cover.
A body rear ends that I can think of right now from '64 to '72. This is accurate as far as I know.
The '64 Chevy 8.2 10 bolt had different splines on the axles than later 8.2 rear ends.
The '64 to '67 Chevelle rear ends were 60 inches wide and '68 to '72 were 61 inches wide. Spring perches were flat from '64 to '66, and from '67 to '72 they had the raised center.
The Chevelle used the Chevy 8.2 10 bolt from '64 to '72 or the Chevy car 12 bolt from '65 to '72.
The Buick, Olds and Pontiac A body used the BOP 8.2 10 bolt from '64 to '68. The Buick used this rear end to '70 and Pontiac used it to '72.
The Olds A body used the O axle with 12 bolts in the cover, 10 bolts in the ring gear and bolt in axles from '68 to '70.
The Buick and Olds used the corporate 8.5 with bolt in axles in '71 and '72.
Decided today to scrap the idea of building a 10 bolt... a friend of mine has 3 12 bolts sitting at his shop...
so I just ordered a 30 spline eaton posi, 30 spline moser axles, 3.73 gears and an install kit for a 8.875 (12 bolt) axle...
now to sell off all my 8.5" 10 bolt stuff...
Eaton Posi (30 spline) - $490
Moser Axles (30 spline) - $250
Summit Racing 3.73:1 gear set - $150
Richmond Gear Install set - $95
Axle bearings and seals
Strange Eng. 1350 Series Pinion Yoke - $80
If you bought axle bearings and seals for a c clip 8.5 then they will work in the 12 bolt. They use the same bearings and seals.
You can use the yoke in the 12 bolt if you use the pinion seal for the front axle in a late '70s or early '80s 4X4 GM truck with the 8.5 front axle (not the Dana 44).
AWESOME!!!! thanks for the info!!
I'm picking up the 12 bolt housing today.... should have it built within the month )
going from 300 to 400 hp... plus 2.73 open.. to 3.73 posi... "oh boy"
:thumbup::thumbup::thumbup::evil:imp:
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