Mattyp77

Hey guys, so I have an 87 Cutlass that originally came with a 307, 200-C, and of coarse an open diff 7.5 rear. I took care offer the first two problems. Put a 425 big block in place of the boat anchor and a th350 in place of the boat anchor behind the other boat anchor. Now I gotta do something with the rear end and I don't have a whole lot of knowledge about them. A few years ago when I started this project I bought a posi unit for like $100 from a guy on eBay. Shouldn't have bought it without doing more research but that was then and this is now. I tried searching all marks on the casing without any luck. From recent research the best clues I can find is that I think it is a series 2 carrier for a 10 bolt unit as there are 10 bolts and the deck height is just over 1-5/8. And I'm pretty sure it's and Auburn by the springs. But what I'm not sure of is a carrier for a 7.5 different from a carrier for a 8.2 or 8.5 and if so which is this and how can I tell. Also is a bop carrier gonna be different from a Chevy and if so which is this? Should I check the spline count? And lastly is this an aftermarket part? Considering I found no results on any of the markings. Thank you

monzaz

Ok - if this is from a 1987
and the pictures you provided.
this is a 7 5/8 Limited slip posi unit for 26 spline axle 7.5 / 7 5/8 rear
The unit is made by Auburn for GM as an original G80 posi

COUNT THE AXLE SPLINE SIDE GEAR TEETH ON THE POSI UNIT...IF IT IS 28 THE UNIT IS FROM A 1990-2002 CAR CAMARO FIREBIRD OR FULL SIZE CAPRICE ETC.

1 3/8" TO 1 5/8" IT IS GONG TO BE A 2 SERIES YOU NEED A 2" FOR A 3 SERIES UNIT.
THEY DO MAKE THICK GEARS IN 7.5 REAR SO THAT REALLY IS NOT AN ISSUE.

7 5/8" limited slip and open carriers had bigger pinion shaft spider gears which made them stronger than the standard 7.5 early Auburn posi units.

This is what the Monte carlo SS received as an upgrade instead of the 8.5 like 442 and GN received. Most of the 1984-1988 7.5 G-bodys with V8 received this upgrade. It was almost standard by 85 86 to just have the 7 5/8 open and posi carriers in the rears.


8.2 chevy, 8.5, 7.5, 8.2 BOP are all different and do not interchange...sorry. all are different widths ring gear bolt patterns ring and pinion etc.

YES the 8.2 and 8.5 and 8.2 BOP have the same ring gear bolt pattern BUT just consider them all different so as not to confuse yourself...Leave the custom stuff to experts...

Jim
J D

olds 307 and 403

I must have had bad luck. My 88 Cutlass, Olds 307 was the only motor option that year, had the 7.5" open and stock 2.56 gears, according to the trunk lid, definitely the smaller spider gears. Also after I broke the 7.5" no slip, I should have got new bearings pressed on and 28 spline axles on the 3.42 open 7 5/8" carrier I picked up of EBay but I was always hesitant to spend money on that glorious axle. After I blew apart a set of the soft stock spider gears, I bought used 3.42 gears from the local wrecker, most 80's Astro Van had 3.23, only some had 3.42 gears. I bought spider gears as well, two sets and matched the least worn together. I think GM used the same forging as Olds connecting rods, soft as hell. I replaced them with much better Yukon spider gears and Amsoil 75W140, they held fine, behind mid 14's with slicks at the track with a girdle cover, an Olds 260 is now keeping it safe till it comes off the road. If you plan on any power behind a 7.5", the 7 5/8" larger spider gears will help, I also used the solid pinion spacer the last time out. There are aftermarket axles in both 26 and 28 spline but a 28 spline carrier and axles make more sense if spending the money. Good luck, you need it.