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Discussion Starter #1
This seems to be a good enough place as any to post for this.

I got an 81 elky and I am pretty sure that it does not come with posi rear end. I would like upgrade to that however and was hoping that someone might have a good suggestion on how to do that? What would make a good donor is what I am wondering I guess. Also, what would i need for a job that big?
Thanks ahead
Steve
http://elcaminocentral.com/users/bigsteves81/
 

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Try looking at the 84 to 87 monte ss. most were ordered with 373s and lots had limited slip rear ends.
 

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83choochoo said:
Try looking at the 84 to 87 monte ss. most were ordered with 373s and lots had limited slip rear ends.
What tranny do you have? If your 81 has it's stock drive train you probably have a TH350. Doing 70 on the highway with a 3.73 rear will give you some pretty high RPM with the TH350 1:1 3rd gear. The MCSS had an OD tranny.

IMHO a 3.08 would be much better. A lot of G-body El Camino and Malibu wagon came with a 3.08 posi. That is the highest I would go for a daily driver with a TH350. Look for a G80 RPO (Regular Production Option) on the Service Parts Identification Label to tell if it's a posi, or the original metal "use limited slip diff lube only" tag on one of the cover bolts is a good indication of a posi too. And look for a 2BV or 2BC gear ratio code stamped into the front of the passenger side axle tube to tell if it's a 3.08

:mrgreen:
 

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Discussion Starter #4
One day I hope to understand what that all meant : )
I caught some of it. I am really a novice at this all. You might hate me for saying this but it is my new hobby.I still have so much to learn : )
 

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Best way to go, and make sure you get a posi?...Look in boneyards, "parts for sale" in newspapers etc etc, and find yourself a complete rear end out of a Buick Grand National, it came with a posi, 8.5" ring gear, and beefier axles, it's a bolt in swap also. Will take more of a beating than the stock rearend, I've seen a few for $500-$600. Also heard that Oldsmobile 442 has the same axle, make sure it's one made after 1978.

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The job itself is not difficult. I've done several rear end swaps all by myself. The latest was putting a 79 T/A disk brake posi rear end in my Camaro. Just make sure you get the pinon angle correct.
 

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theelcaminofactory,
Brings up an interesting story that happened to me a couple of years ago. My son allowed our mint 91 caprice to get Teeboned which ruined two good doors. We went the St Louis Police Tow auction looking for car since it cheaper than the $1500 local Junkyareds were asking for a pair of doors. Low behold I saw an 85 Cutllass 442 with my dream rear end! My brother-law said you'd better make sure we looked at a 79 Malibu parked next to it. DAMN it has to one too! Thinking I have lost sense in recognizing the 8.5" rear end covers I checked another Cultass and my sanity was confirmed. Now had two to choose so I had to figure out which one was best. The Cutlass turned our to be a 3.42 open and the Malibu a 4.10 posi. Also the Malibu had a stripped interior, high dollar mufflers and under the hood were were resting a pair of big block headers. I had indeed found stripped street racers car. When bidding I fought some fierce competion form local JY dealers who difinitely were in the know, so instead of paying my target price of $60 I ended up having to buy the car for $150 which I sold a week later for $100 minus the rear end of course. The Cutlass 442 went for $450.

on 7.5"'s look around. I have actually had good luck finding posi's in Chevy Monzas. You really only need the posi unit. I typcally look for the limited differatial lube only tag on the rear cover and if it's not there I move. Once found I pull the unit and remove the bolts holding the unit together so can inspect the cone clutches since they are not rebuildable. To reinstall you need to use the old ring gear and will need a mic to measure shim thickness and dial indicator to check backlash. You should not have to worry about pinion depth.
 

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Should mention that if you can't find exactly what you need in a donor car, US Gear and other manufacturers make posi carriers for most GM rears. Usually run about $400 for a new unit. Then you install it in your existing housing, or have a pro install it fo you and you have a new rear end. I've seen several "used" posi rearends that have been abused.
 

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I just pickup an Eaton posi from Tom's Differential for $314 a few weeks ago. A set of 3.42 gears cost me $154 (I think) from Tom's also.
 

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website for Tom's ?

I just pickup an Eaton posi from Tom's Differential for $314 a few weeks ago. A set of 3.42 gears cost me $154 (I think) from Tom's also.

i'd def like to get to know more about this- did u mean you bought posi kit for $300+ then a set of 3.42 gears for $154? did u have it done by a shop or something yet? what would the labor cost-wise be on this?

thanks for sharin the info
 
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