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factory 8.5 30 spline posi?

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81rustabu
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factory 8.5 30 spline posi?

Post by 81rustabu » Tue Mar 20, 2018 9:18 am

Did GM ever make a good factory 30 spline 8.5 posi. i think my factory auburn has finally went.
IM ALL JACKED UP ON MOUNTAIN DEW!!!

81 malibu 2dr 350 with vortec heads .40 over, th350 3500 stall, gn 8.5 posi 3.42
12.97@101.67 on motor and 11.80@112.27 on a 150hp shot of nitrous
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prairiehotrodder
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Re: factory 8.5 30 spline posi?

Post by prairiehotrodder » Tue Mar 20, 2018 2:08 pm

are you sure yours is 30 and not 28 ? I don't know the answer to your question because I've only seen 30 spline in 4x4 trucks and they usually have a govloc. If you indeed need a 30 spline posi I would go aftermarket. Eaton, Auburn or a powertrax lockrite in an open carrier are some options.
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81rustabu
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Re: factory 8.5 30 spline posi?

Post by 81rustabu » Wed Mar 21, 2018 11:58 am

I do have a 30 spline posi with aftermarket moser axles. My posi came out of a mid 90s caprice witch do have 30 spline axles. I'm just wondering if they made any better posi units that are factory?
IM ALL JACKED UP ON MOUNTAIN DEW!!!

81 malibu 2dr 350 with vortec heads .40 over, th350 3500 stall, gn 8.5 posi 3.42
12.97@101.67 on motor and 11.80@112.27 on a 150hp shot of nitrous
street beater

Rusty but Trusty

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DOUG213XRJ
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Re: factory 8.5 30 spline posi?

Post by DOUG213XRJ » Wed Mar 21, 2018 2:47 pm

I would bet the aftermarket limited slips are stronger then GM.


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Re: factory 8.5 30 spline posi?

Post by Doober » Wed May 15, 2019 9:43 pm

I'm planning on a Detroit Truetrac whenever I build the 8.5 I have. No clutches and should hold up fine for the street, if I raced I would probably get the Detroit Locker, to my understanding it's stronger than the Truetrac.

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Re: factory 8.5 30 spline posi?

Post by LS6 Tommy » Sun May 26, 2019 10:02 am

Truetracs are kind of weird. Most gear style limited slip diffs are. They sometimes growl or make funny noises, they sometimes make the car feel loose or move around when you lift off the gas in a corner. My new STi has a gear diff in the back and it does the same things as all lthe other gear diffs I've driven.

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Last edited by LS6 Tommy on Tue Jun 04, 2019 9:02 pm, edited 1 time in total.
20k mile '80 Malibu, currently undergoing long term (aka no money) factory style install LS6 454, Cowl Induction, Legend LGT 700 5 speed. Full Global West suspension, 17" N90 wheels, 12" front/11" rear disc brakes, 9" 3.70 Auburn Pro posi.

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Re: factory 8.5 30 spline posi?

Post by malibu795 » Mon May 27, 2019 6:35 pm

The true track is definitely "different" in feel from regular clutch/cone posi..
Dodge uses the torsion diff design in there 2500/3500 trucks exclusively.

Never had one make noise... Had a ratchet diff make noise but that's not a torsion doff
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Re: factory 8.5 30 spline posi?

Post by prairiehotrodder » Wed May 29, 2019 7:39 pm

Auburn has a cheaper one and a better one. Not sure what differences there are besides price.
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Re: factory 8.5 30 spline posi?

Post by LS6 Tommy » Tue Jun 04, 2019 9:03 pm

prairiehotrodder wrote:Auburn has a cheaper one and a better one. Not sure what differences there are besides price.

X2. Everybody goes for the Eaton, but the Auburn Pro series has much higher torque biasing.

Tommy
20k mile '80 Malibu, currently undergoing long term (aka no money) factory style install LS6 454, Cowl Induction, Legend LGT 700 5 speed. Full Global West suspension, 17" N90 wheels, 12" front/11" rear disc brakes, 9" 3.70 Auburn Pro posi.

"The older I get, the faster I was"

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