[WillV]

Anyone here recognize this rear end - what year, make it will work for. I mistook it for a regular A body differential but now noticing the differences between the two... one being where the coil springs mount. It's a posi rear end with 4.10 gears. Thanks.

['ol Pinion head]

The housing is basic '73-77 8.5 A-body Chevy (c-clip axle) rear, will fit '77+ B series, as well. The bolt-in axle version of '73-77 A-body housing has two spot weld plugs on each side of the center housing when one looks at it from the rear cover side, your pic only shows one plug hole on each side.

Are you sure its a 4.10? Ring gear does not look that thick & the gears are GM part numbered. Looking at the top (rh side, installed) of the carrier, there will be large numbers cast into the end of the S spring 8.5 posi carrier. If the number is a #9, the rear is a 2.56 posi, & from info provided in your earlier post, I would bet out of a '77 Impalla or '77 A-G body. I used to pull a ton of #9 posi's out of '77 Impallas that had Chebby 350's. Smaller engined '77 Impalla's had the dinky 7.5 rear, as well as did all the other small engined B series rears of that era.

[WillV]

Thanks for the response. Here are some #s that are stamped on the big gear:
3984822 16 41 10 76 -

[ponyakr]

Originally Posted by WillV

Thanks for the response. Here are some #s that are stamped on the big gear:
3984822 16 41 10 76 -

Divide the 41 number by the 16 number and I think you'll come up with 2.56 gears.

I think the small number is the number of pinion teeth. And the big number is the number of ring gear teeth.

I've read that all the 8.5" 10 bolts have these square cornered ears on 'em.

['ol Pinion head]

Originally Posted by WillV

Thanks for the response. Here are some #s that are stamped on the big gear:
3984822 16 41 10 76 -

3984822 is the # on a 2.56 8.5 ring gear.
16 41 is as pontyakr noted a 2.56

Looking really closely, one will see a little wider than an 1/8" wide groove machined in the side of the ring gear. GM only did that on 2.56's & 3.23's in the 8.5 gears.

the 10 76 is the date of mfg... a '77 rearend.

On the square "lugs" on the bottom corners of an 8.5 housing...
Not every 8.5 housing had the squared off big lugs, there were several that the housing was cast differently & no lbig lugs. Then there are several off us who have been grinding the lugs off & reshaping the lugs for the last 20+ years to look like those on a more common 8.2 10 bolt.
BTW, all the type "O" Olds 10 bolts (12 bolt smooth cover) also had the big square.lugs, as well.

[WillV]

Thanks guys.. arrgh.. so I screwed up and this rear end will not work on my friends project.. and I told him to buy it.. frock! Any idea what this rear end is "really" worth?

['ol Pinion head]

There seems to be a market, today, for the higher ratio A-body posi rears for the driver/cruiser crowd. 2.56-2.73-2.78-2.93... In builds, I've usually chunked all but the 2.93 ratio gears in my scrap barrels. To box em up, they had to be nice tight pattern set, and 8.5 corporate 2.93's are not an easy find.

Will, you might ck local bulletin boards & Craigslist for what a decent used highway ratio '73-77 A body 4 3/4 bolt pattern posi rear is selling for.... In CA, I'd hazard...maybe, $275-300, in decent used shape (unless your name is Frank). If this rear had been the earlier style 8.5 A-body rear with the factory S spring posi & highway gears, would go for quite a bit more as the early style housing & axles are worth considerably more. Hope this helps.

[WillV]

Hey OPH... tried to PM you and couldn't as you are over your limit. Just had a quick question, or anyone who might know about this rear end. Looks like rear shocks mount from the front side and not from the back - like the early year A bodies.

['ol Pinion head]

Will, '73-77 A-body has shock mounts on the front, that's what is in above pic. Earlier A-bodies have shock mounts to the rear. Clearing out some PM room.

[WillV]

Thanks OPH