85 ss monte carlo rear end suggestions

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the nitro man

85 ss monte carlo rear end suggestions

Post by the nitro man » Mon May 02, 2016 4:47 pm

i have an 85 ss monte carlo & i'm building around a 400 horse 357. the car has a 7.5 3.73 gear, open carrier rear end in it from the factory. would one of those powertrax lockers be ok for it & it live, or should i get one for a 4.625 (7 5/8" if it will even fit in the 7.5 carrier) & get a set of 28 spline axles out of a 86 up g body rear.

this car isn't going to be on the drag stripe every weekend, it will just be a street car that i might take to the track a couple times a year.

i have found a after market nodular iron 9" ford center section, my choice of 3.70, 3.75, 3.80, 3.89 or 400 gears, 31 spline Detroit locker & a Daytona pinion support for $500.00 bucks shipped. seems like a steal, but then i would have to get the rear end housing & axles & then i'm in it for around $1,300 bucks. not to bad i know but i'm on a budget.

damn i hate being poor

77cruiser
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Re: 85 ss monte carlo rear end suggestions

Post by 77cruiser » Tue May 03, 2016 11:44 am

If you are lucky you might be able to find one from a GN, that would a 8.5.
Jim

the nitro man

Re: 85 ss monte carlo rear end suggestions

Post by the nitro man » Tue May 03, 2016 3:38 pm

you're right, it will fit, but it would be about $1,000 bucks.

ChevyEFI
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Re: 85 ss monte carlo rear end suggestions

Post by ChevyEFI » Wed May 04, 2016 8:46 pm

Most importantly, do you plan on running slicks?
And do you pan on running a zero offset 8" wheel at best?

The stock rear is narrow and isn't ideal for adding more wheel width.

Most any upgrade from 8.5" GM 10 bolt to GM 12 bolt to Ford 9" will be fine to replace your 7 & 5/8" 3.73 rear.

28 spline axles were used in the 8.5" Buick/Olds rear. Never factory installed in a G-body 7.5 / 7.625.

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Re: 85 ss monte carlo rear end suggestions

Post by F-BIRD'88 » Wed May 04, 2016 9:01 pm

Replace the open diff with a Aftermarket Auburn posi or Eaton Posi.

The stock 7.5" 26 spline rear is fine. It will take a lot of power but not repeated SHOCK.
(Wheel Hop) (manual trans clutch dumps)

Eliminate wheel hop with correct lower control arm reloaction brackets, new control arm bushings
and rear air bags.
The OEM diff and limit slips (dana) are weak. The weak link.

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Re: 85 ss monte carlo rear end suggestions

Post by crazyman » Thu May 05, 2016 4:34 am

77cruiser wrote:If you are lucky you might be able to find one from a GN, that would a 8.5.
I agree. Second to finding a still weak unicorn (GN), Currie makes drop in 9" units.

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Re: 85 ss monte carlo rear end suggestions

Post by peejay » Fri May 06, 2016 1:44 pm

The GN rears would hold up fine at that power level.

I think the 9" would be a better bet. No more C-clips.

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