8.5" rear end question

[fonz3482]

hello everyone,
A distant friend recently pulled a 8.5" rear end out of a car. He said it is posi, he is unsure on the gear ratio, and it worked fine when he pulled it. Whelp, the rearend ended up outside all summer,fall, and winter, in tall grass. Sooooo, It needs brake work, backing plates, possible gear change, a good clean up, paint job, and spring perches. My question is: he told me to make him a offer on the rearend and I'm unsure on what to offer him in its current condition??? He seems to think its a very rare rearend, so it scares me to offer him a lower price and insult him. Another option I have is my dad has a 12 bolt with 4.11 gears, and posi out of a pontiac gto. It will also need most of the repairs that the 8.5" needs, but he will give it to me for nothing. Problem with the 12 bolt is, it doesn't bolt in like the 8.5 will and the control arm kit will cost around $350 I believe. So What should I do?? I guess the 12 bolt is supposed to be stronger, The gear ratio is alittle high for street use, but I can live with it, They sell a nice disc brake kit for the 12 bolt for a decent price, and the control arm kit appears to be a good upgrade to my cars stock suspension. Now the 8.5" im not sure on, I beleive they are somewhat strong, and bolt right in, which is easier in the long run, but im not sure if its cheaper after I pay for it and do all the work to it that it needs. So, what would everyone do, and How much do I offer?? Or do I even bother with the 8.5" at all?? Any input would be great,
Thanks

 

[stubnosebrock]

It will depend on what he pulled the rear from as to if it will be a bolt in installation for your car. If it is indeed from a G Body( Grand national/442 etc.), than yes it will bolt right in, and yes it is a bit rare, but since its been sitting probably isnt worth much more than $500.00. If its from anything else, it isnt rare at all and since its not a bolt in deal its worth considerably less for you. Being able to bolt it right in is gonna make all the difference. If both need to be made to fit, then whatever one you can get cheaper is probably the way to go.

 

[fonz3482]

All I know is it came out of a cutlass g-body car. Im thinking of offering about $200. If he wouldnt take that then I think Im better off with the stronger 12 bolt.

 

[stubnosebrock]

If its from a G body thats an easy bolt in deal. What kind of power are you planning on making and what are you doing with it? The 8.5 10 bolt is very strong, and I think when built right will hold up close to as good as a 12 bolt.

 

[Kris_84elky]

In case you didn't know BOP 12 bolts have a 10 bolt ring gear in them but I believe they are the same 8.5. Chevy 12 bolts have 8.875 ring gears.

 

[robhowardiii]

Rember a g body 8.5 needs a 1" shorter driveshaft. 12 bolt swap arms are less than $200 check iceman racing on eBay (search 12 bolt swap arms) or umi makes them. It's only the uppers you need and a conversion ujoint (i got mine at autozone for $10)

 

[fonz3482]

Well I talked to my dad and the 12 bolt came out of a chevelle and he put it into a 1970 gto judge. When he sold the judge he pulled it out and stored it away. It eventually ended up in my incles storage shed where its been burried for years. He says it worked awesome and was very strong and reliable. I guess his gto had a pretty nasty 455 big block in it and the rear end never gave him a problem. I plan to run a sbc with hopefully around 450hp of output. Im going to check out the 8.5" this weekend. If the gearing isn't right I'd probably just pass and stick with the 12 bolt.

 

[Bweavy]

If you pass on the 8.5 let me know I would be interested in it.

 

[79malibubbctt]

Id say 100. Youre going to have at least another 200 by the time you do all the other stuff. Do you have a upullit or salvage yard around. Sometimes you can find good stuff in there. My upullit gets 125 per yearend. Either or uts going to cost about the same but the other should bolt in.

 

[dogsht]

The gearing if factory will either be 3.42 ie out of a GN/Ttype or 3.73 out of a 442. Factory posi is probably less than a 50/50 deal. If the driveshaft is still with it or around and even the better factory 200-4R that is the ideal platform for a hot street car that is a real driver ie more than just stop light to stop light. I used for a while a 3.73 with a big block Caddy 509 because the .67 overdrive from the 200-4R made a final drive ratio 2.49 subtract out another 200 rpms from the lock up converter and it pulled off 17.0 mpg on a hwy interstate trip once. It also had a mild cam and Q-jet to help but still not bad from big cube motor car that also ran 12.5 at 110 in the quarter.

If you go the custom 12 bolt route and it has low gears like 4.10s and no easy way to overdrive without also doing a driveshaft etc it won't make as nice of a driver but if you have some welding fabricating skills you can probably get it in and up and running cheaper. Comes down to goals and money or goals and equipment / ability as to whats the best route.

BTW you can always get good money back out of the 8.5 on here or CL and quick. I listed one in good shape for $700 and had cash in hand in less than 24 hours.