8.5 10 bolt posi rear end build or new options?

[tbal]

Hey guys,

Have a 383 pushing about 550hp through a built th400, and now the rear end is doing some fantastic stuff, and on its way to take a dump. (It was a matter of time).

Now the question is do I swap out the axles, and add new posi etc etc and call it a day? OR do you have any suggestions of a complete overhaul to possibly a 9" etc with all new housing and so forth?

BTW I Have a ridetech 4 link currently installed... which is going to be a bitch to swap if I don't stick with the current housing... This looks like an interesting starting point... http://www.hotrod.com/articles/build-bulletproof-gm-10-bolt-axle-built-c-clip-eliminator/

Cost... not too concerned, but lets say under $4000....

Thoughts?

[AU Doc]

For $4k, you can put together a super strong and extremely light 9" in a fabb'ed housing. But if you're wanting to spend that money elsewhere, I'd build the 8.5. According to the internet and the articles (similar to the one you've linked), it should be more than adequate.

[Canon_Mutant]

What I am doing . . . for behind a custom BBO in my 442. Only 400HP at the moment but over 500 lb.ft.

Eaton Truetrac
Moser 30s
Strange 30 Yoke
Auburn 3.42s [from the factory 3.73s]
LPWracing Standard Depth Brace and Cover [support for the tiny tubes]
Also moving to a Strange 1350 joint shaft while I'm at it

then bolting it up with

UMI Boxed Lowers w/ poly front roto rear
UMI Adustable Uppers w/ poly rear roto front
UMI Lower to Upper Reinforcement
UMI Protouring Antisway design
UMI Shock Tower Brace
Bilstein AKs
Eibach Pro SS Springs
1 1/4" box brace between the rear rails [effectively a hitch bar without the hitch but pretty effective for what it is]

Unlike my 8.5 factory internals that I found out were apparently made from cheap soft crap junk when I "fortunately" tried to just put on a decorative cover, I am confident this will hold up. I say fortunately because the car is only at 28K miles and less than 4K miles behind the big block so I thought it would be fine. You should have seen the metal that came out with the fluid . . . pretty scary.

Good luck to you!

[Interceptor5588]

Buick guys have run the 8.5 down to the 8's

[csouth]

I'd build the 8.5 and put the money elsewhere. You can get axles, new RP and posi in for half that and it will handle the power you're making. Its not the HP you need be concerned with so much its the torque that breaks things.

Like what Canon Mutant listed in his specs. People will look at his and say "oh that's only 400hp..." Yeah, but 500lb ft of torque is behind it.

[Decline]

8.5's should be plenty strong. I'd build that and save the dough
My camaro had the crappy small 10" so it was not worth building. (Sold it complete with drum brakes for $150):rotfl::rotfl:
That hot rod article was cool but if your gonna pay someone to do all that it prbly be cheaper to just buy a 9".
If you want to go all in....
I used motive gear ring and pinion with a tru track in speedway engineering floating 9"
My floater was $1800 complete and they welded on the brackets for my torque arm. My third member is an aluminum strange hd that I got from quick time assembled with the aforementioned gears and diff for $1500.
The only catch with this is you need a specific brake kit from wilwood for this setup that was another $1500
Jdman built a moser circle track 9" floater for considerably less using z06 rear calipers and custom brackets. I think that housing/axles is around $900
If your gonna go all out 9" floater is the way to go. Bullet proof, No pad knock back no leaks and no risk of loosing a wheel if you break an axle

[hifi875]

nothing weak at all about a 8.5 10bolt at all

[TheJDMan]

I would never even consider building a 10 bolt, but what ever.

[csouth]

8.5's should be plenty strong. I'd build that and save the dough
My camaro had the crappy small 10" so it was not worth building. (Sold it complete with drum brakes for $150):rotfl::rotfl:
That hot rod article was cool but if your gonna pay someone to do all that it prbly be cheaper to just buy a 9".
If you want to go all in....
I used motive gear ring and pinion with a tru track in speedway engineering floating 9"
My floater was $1800 complete and they welded on the brackets for my torque arm. My third member is an aluminum strange hd that I got from quick time assembled with the aforementioned gears and diff for $1500.
The only catch with this is you need a specific brake kit from wilwood for this setup that was another $1500
Jdman built a moser circle track 9" floater for considerably less using z06 rear calipers and custom brackets. I think that housing/axles is around $900
If your gonna go all out 9" floater is the way to go. Bullet proof, No pad knock back no leaks and no risk of loosing a wheel if you break an axle

The Speedway floater is probably top dog, I'm sure you're smiling. ... Moser floaters are great and mine is built similar to Steve's (TheJDman). The biggest issue with them is the lack of parking brake(for guys with manual) and finding a caliper bracket if you can't design your own. I was able to get some from GMR for mine, but they have since closed shop.


I would never even consider building a 10 bolt, but what ever.

Hey Steve, I sent you a PM about the parking brake brackets recently, didn't know if you saw it?...

[sam 74]

i had a 8.5 behind my 470 inch BBO, in my Cutlass. it held up for a few years with an Auburn Posi, 3.90 richmond gear, and Timkin bearings, but it still had 28 spline axles, and a support cover. i started using slicks and i twisted the axle splines into the carrier and that was the end of that rear end, nothing else broke or looked bad so if you upgrade to say 31 or 33 spline axles and build it right it will last, i put just north of 550 ft lbs of torque to it.

[Skip Fix]

I've been running my 78 TA with stock 28 spline axles and an Eaton posi in the high 10s with slicks. It is getting a new 30 spline Eaton and axles. Seen guys in the low 9s with tehm and a 30 or 33 spline spool.

If you are going to use rear discs and a hubcentric wheel the Mosers won't grab the wheel pilot is too short-and they say "just switch to lugcentrics". Dutchman can make them custom pilot length. 0.700 -.0750 will get it and the length of the 79-81 Trans Am 4c WD pilots.