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what rear end is this?

4K views 19 replies 4 participants last post by  big gear head 
#1 ·
I am trying to figure out what rear end is in my car so I can order some 3.73 gears for it. It seems to be a 8.75 with a posi unit and 2.73 gears. It has a 10 bolt cover and has 12 ring gear bolts. 3 inch axle tubes and c clip axles. The only axle tube numbers I can see are 2tw. I have not pulled an axle out to check spline count. Are there any 3.73 gear sets avaliable for this series carrier or can I use a ring gear spacer? Is it even worth the time? If this is a 8.75 rear end what the heck is it doing in a 82 caprice classic? Maybe im better off selling it to someone else for there project due to its lack of aftermarket support. Any help would be appreciated.
 

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#2 ·
I'ts the early 1970's oddball 10/12-bolt hybrid. I believe called a Type "O". There is zero aftermarket support for this rear...nothing beyond bearings and seals.

Some ID help here in this sites wiki : http://www.crankshaftcoalition.com/wiki/Rearend_identification#8.75_inch_10-bolt

Unless it is the correct length, has correct brackets to fit your application and a gear ratio you want in it already you would be better to sell it off...if you use it and break it you'll lose that possibility.

Be better to let a street rod builder have it.
 
#3 ·
Thanks for the reply ericnova. That wiki site is very helpful and is where I found pretty much all off my info on this rear end.
Whats weird is this rear end is what came in my car when I bought it a few years ago. Someone must of swapped it in a while back. 2.73 with a posi would probably be good for something with a 4 speed and a decent power plant but in my caprice with an overdrive tranny not so much.
 
#5 ·
The Type O (as in Oldsmobile) has a 12 bolt cover and a 10 bolt, 8.5" ring gear and was only used in 1966-1970 Cutlass/442 cars. This axle clearly isn't one of those. Some of the full size cars did get a 10 bolt cover, 12 bolt ring gear axle. Try DTS for parts.
 
#6 ·
Tried dts for a ring and pinion but no luck. I would put a impala ss rear in my car but I dont want to deal with the different wheel bolt pattern or the disc brakes and not to mention they are rare in my area and the only one I could find was very expensive. I do have a 7.625 rear from a 90 caprice (I think its a 7.625 anyways). It also has 2.73 gears but I am thinking of going 4.10s now. That would give me 2400 rpm at 70... not bad I guess. An engine swap with 300-350 horse is in the future. You guys think a 7.625 with a eaton posi or a powertrax with hold up ok with that kind of power to it? Once again thanks to you guys that have replied, your advice is very helpful.
 
#7 ·
The 7.5" should be okay at that power level, over 400 hp would lead to problems with a heavy car and good traction.

I thought the 90 Caprice would be an 8.5"?? or is that only the higher hp models like Police and the SS Impala with the 5.7 engine. I know the 5.7 wagons (Buick Roadmaster and Chevy Caprice) have the 8.5"
 
#9 ·
I think the 7.5 was standard in everything but the wagons and impala ss. Also the wagon rears wont fit in the sedans.

I found one 8.5 near me but the dude wants $700 for it. Its a posi and has 3.73 in it. Mite go for it since I would be in it for less than a set of gears and a posi unit for a 7.5.
 
#13 ·
I have been told the lower control arm mounts are wider than on a sedan axle, not sure of the truth behind it though.
I looked at the ss axle agian and it is missing the rotors, calipers, caliper brackets, and backing plates... not good. But the more I think about it the axle is decently priced except for the missing parts.
 
#15 ·
You can put drum brakes on the SS rear end. I built a drum brake rear end for a SS and put the SS disc brakes on it. They were a direct swap. I'm not sure, but the 8.5 truck drum brakes might fit. I think the Impala rear end has the larger bolt pattern for the brake backing plate.
 
#16 ·
That would be cool if the drum brakes bolted on the ss axle. I think the ss has a 5 on 5 wheel bolt pattern and my car has a 5 on 4.75 pattern. Is a machine shop capable of redrilling the axles to a 5 on 4.75 pattern?

Also how can you tell what posi unit is in the ss axle by just looking at it? I guess someone put in some 3.73s and the posi looks aftermarket. I just want to make sure it doesnt have an auburn or an ebay "eaton posi-style" in it.

Thanks again
 

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#17 ·
That would be cool if the drum brakes bolted on the ss axle. I think the ss has a 5 on 5 wheel bolt pattern and my car has a 5 on 4.75 pattern. Is a machine shop capable of redrilling the axles to a 5 on 4.75 pattern?

Also how can you tell what posi unit is in the ss axle by just looking at it? I guess someone put in some 3.73s and the posi looks aftermarket. I just want to make sure it doesnt have an auburn or an ebay "eaton posi-style" in it.

Thanks again
 
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