Hey Guy's I am in the Market for a Posi rear to replace the Peg leg in my 85 El Camino. I have been told that my rear is a 7.5 and the 80's And G body HO car's had 7.5/8 rears which were a little heavier than mine and they were posi. I would like this rear to have come from a tuned Port 350 car but will also consider a Monte SS. posi. I am hoping that I can combine one of these posi unit's with a set of beefier aftermarket axles and with any luck it will live on the street as long as I don't put drag radials or a train break in it. LMK what ya got or shoot me an E-mail at shuspeed@hotmail.com.........

 

Ralph,

You don't want the third gen rear for a couple of reasons. First, it's no stronger than your rear in the 'Camino. In fact the internals are exactly the same as yours. Secondly and most important is it will not bolt up to your 'Camino. 3rd and 4th generation F cars use a three link suspension. Your's is a four link.
Now you can replace the "guts" from a ten bolt third gen into your's if you are looking for a cheap posi replacement. Check the link below for your options:

http://www.maliburacing.com/tech_rearend_swaps.html

 

Hmm I have seen this already and I know that the rear is not a real top performer. What someone has told me is there are two verieties of this rear. First is the 7.5 diff peg leg that I have and secound there is the F-body 7.5/8 which is a Posi on the HO cars. A couple of people have told me that it is possible to pull the peg leg out of the Elco and pop the posi of the slightly stonger F-body. I was thinking that I would pop in some good axles to top it off. This is not a drag race car just a street runner that will be in the 400 hp range. If I break it I will have to go to a 12 bolt or a Ford nine. My Firebird has a nine inch and makes a whole lot more torque than a small block Chevy.

 

Ok...I get what your after now. Your use of the period in 7.5/8 threw me. You want to swap in a 7.625 or 7 5/8" guts into your Elky rear. Totally doable but you must match the Series of carrier with the series of gear. For instance, if you have a series 2 gear in your Elky, you have to find a series two posi carrier. This thread should clear things up.

https://www.thirdgen.org/forums/tran...-10-bolts.html

 

Exdactly and I am aware of the carrier gear match up Thanks. What gear would you run with a 700r4?

 

I'm doing exactly what you going to do on my 1979 El Camino. I found a good used Auburn posi and 3:73 gear on this site and am installing them in my El Camino rear. Another area of concern is making sure when you purchase axles, you get the right spline. My '79 Camino had a 26 spline axle and the Auburn is for a 28. I wasn't planning on buying new axles yet but I guess I am now.

My 66 Camino has a 200R4 with the stock stall speed. It does really well with the 3:73 gear. I personally wouldn't go lower than 3:73. I had a 4:10 gear in my 1985 IROC with a T5 and that 1st gear was near useless. Your 700R4 has a deeper first gear than my 200R4 so going lower than 3:73 on the street wouldn't get you much in performance, in my opinion. If this were a strip car, I would have a different opinion because of the grip you get with slicks.

 

Will you doing yours very soon? Let me know how things go because I have been debating on what way to go and to be honest this has to be a budget build because all of my real dough is in a complete restoration of a 69 Firebird. As far as racing it goes I do not think I would do this with this rear end period. It is a very week option IMHO and I wouldn't think that it would hold up that well with slicks or Drag radials. I was thinking about buying an eaton posi and using a set of Moser axles with a T/a cover. I would think this would be good to 400 or so hp provided that you don't hit it with slicks and or a trans brake? Another thing I will have an issue with is doing the job itself I have never done this and from what I understand a weak rear to begin with if not set up perfectly will be that much weaker if all is not perfect? Have you done this before? If so I'm all ears. I would love to learn how to do it but I think unless it looks real easy i will send it on down to a bud of mines shop and have him do it... Let me know how things go.
Thanks

 

I built my 85 IROC rear as you described. Auburn posi, moser axles, Richmond 4:10 gears, TA cover and ARP wheel studs. I worked it over very hard with no complaints. If you can find the article from Chevy High Performance called, 7 1/2 Is Enough, it describes the best way to build one up. It's the blue print I used. My motor put out 375 at the wheels and with the T5/Spohn upgrades, there was no take up. The rearend took all the shock.

 

So you have been there and done this was it a difficult job to do? What was needed for tool's? How long do you think a posi from an 80's F-body with some good aftermarket axles would last Can this set up handle some strip action??

 

I didn't do the build up. I have a friend who does the assembly for me. His labor rate is so cheap, it didn't seem worth the trouble gathering the proper tooling. He gets the job done is a few hours but it's his job.

I never put slick on the rear. I bet it wouldn't take that kind of abuse. My IROC did see some strip action but only street radials.