what rear do I have?

[junk racing]

When I bought the roller he told me it was an 8.5, Truly i didnt know how to tell...But know im ready to build it so i need to know what im dealing with....I did a search and it has the squared ends at the bottom like an 8.5 but has the diff cover like an 8.2....so im confused

Sorry the pic is so bright, you can barely see the two squared ends on the bottom of the housing...


Thanks for your help guys

 

[Fla_G-body]

It is a 8.5 you can tell a 8.5 front all the other by the two small ears on the bottom of the housing

 

[junk racing]

Thats what i was thinking but a buddy came over and said it was a 8.2 due to the cover, i guess someone swaped covers or something....Glad to know its an 8.5.


One more question, I was under it earlier and noticed the upper control arms have been cut and welded shorter whats the reasoning for that? And thats another reason i thought it may be an 8.2 but it has the ears....

 

[Fla_G-body]

Not sure maybe they were arms off of something like a chevelle or something. Has the car been lowered? They could of been cut to get the pinion angle right.

 

[junk racing]

no the car was drag raced since 1990, I have no idea why they did this unless like you said it was to change pinion angle the cheap way....

 

[monzaz]

That is because it is NOT a GN rear it is from either a 1971 1972 Olds cutlass or Buick Skylark or it is a 73-77 A-body gm Monte carlo grand prix regal etc. Jim

Need to see more of the axle tube and BACK of backing plate area. Need to see the spring perch area too.

REASON I know this??? The axle tube is 3" ALL GN 442 8.5 rears are 2.5 inch in diameter.

Post more pictures and will narrow this down. HOW wide is the rear backing plate to backing plate?

TAke care, Jim

 

[bowtie81]

Got this link from tommy, this should answer your question.
http://www.oldsmobility.com/old/10bolt-tech.htm

 

[monzaz]

Got this link from tommy, this should answer your question.
http://www.oldsmobility.com/old/10bolt-tech.htm

First dot on that site is already wrong. lol.

Truck carriers 1974-2011 will fit all 8.5 cars 28 or 30 spline.

Second bullet is AGAIN wrong 56.5 is NOT the flange to flange for the 64 65 66 it is 54.25 - 54.5 they are 59.25- 59.5" over all drum to drum. 1967-1972 were all the 55.25-55.5 60.25-60.5 drum to drum

Then the next bullet they say that the 12 bolt guts from truck will not fit the 12 bolt guts from the car. YES and NO the posi and open carrier case are not interchangeable BUT the spider gears and clutches are in the open and posi ...lol.

SEE what I mean YOU have to dig deeper. When all you do is rear diff stuff day in and day out ...we just roll our eyes and laugh at the info out there... 1/2 my business is fixing other people blunders where they bought the wrong parts and installed the wrong pieces the wrong way. pretty sad cause they got SOME info from the net...NOT ALL of it.

There are SOOOO many sites with BAD info out there you really need to be careful. There is no way you can ever write down ALL the different configurations out there and beside this rear is not original to his car or a g-body it most likely has been chop cut welded upon etc.

You can use the sites as a guide but be VERY careful how far you trust them with the info.

Hope you post the pictures to determine exactly what 10 bolt 8.5 rear you have.

It is 10 bolt 8.5 absolutely.... But it could have bolt in axles c-clip axles could have 28 spline axle 30 spline axle...and so on.

Good luck, Jim

 

[prairiehotrodder]

can you please post a pic of the car? Or give a description? Does the car look like this---


I swapped a 77 ish 8.5 into this brown malibu about 13 years ago. We eventually put in 4.10 gears with a ring gear spacer on the stock 2 series posi carrier. The 8.5 had stock bolt-in axles like a ford 9". Then the car got sold and i never knew where it went. I cut and shortened the uppers to fit the wider spacing on the diff just like what yours is. (i'm not to proud of it either)
brian

 

[prairiehotrodder]

If that is your car, and by the looks of the diff I'm thinking it is, I can give you its whole history. I have been looking for it for a long time.
brian