Differential gears limited slip to posi traction

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dms2871
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Differential gears limited slip to posi traction

#1 Post by dms2871 » Fri Sep 16, 2011 10:03 pm

i have a question for anybody who knows im building a street strip car its a 1972 pontiac ventura II has a straight 6 in it but going to a v8 hopefully 435hp. ok im using the original rear end finding this out its only limited slip i need posi and need th know the gear ratio on this rear end, and how to convert it to posi traction if possable. i was told to use 3:73 gears in it. as it will also be used on the street. also looking at the b&M transmission #113001 is this a good setup?

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Craig W.
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Re: Differential gears limited slip to posi traction

#2 Post by Craig W. » Sat Sep 17, 2011 8:52 am

Posi-Traction was just GM's name for the limited slip differential. So they are the same thing.

Most likely, you have an open differential, which does not apply power to both wheels and will let one wheel spin.

Converting to a limited slip isn't too complicated and if you're going to change gear ratios anyway, do them both at the same time.

3.73s are a good street/strip gear. It'll be a big improvement over whatever original gear is in the car (probably 2.73s or 3.08s), but also keep the rpms reasonably on the highway.

You can read up on changing gears and setting up posi units on my website. There are also quite a few other tech articles there. http://www.2quicknovas.com/tech.html

You can probably beat that B&M tranny on price and shipping by finding a good reputable local transmission shop. Talk to local racers and see who they recommend.
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Re: Differential gears limited slip to posi traction

#3 Post by dms2871 » Sat Sep 17, 2011 10:53 pm

wow thats a lot of info on your site! so im replacing the whole center stuff with 3:73 gears like a detroit trutrac? how do i find out witch brand i need to fit rear end?

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Re: Differential gears limited slip to posi traction

#4 Post by Craig W. » Sun Sep 18, 2011 7:55 am

A '72 Ventura should have the 8.5" 10-bolt. Nice and strong.

As for what brand of gears and what brand of posi unit to buy, it can boil down to how much strip use you think there will be and how much street driving.

The Detroit Locker is very strong but isn't super smooth on the street. The True Trac is smooth but not as strong. The Auburn is a good differential for the occasional racer. Same for any of the clutch style posi units. They tolerate some strip use but will eventually have problems due to uneven traction during the burnout.

I'd suggest upgrading to 30 spline axles while you're spending money on the posi. It'll keep you from having to spend it again later on.
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Re: Differential gears limited slip to posi traction

#5 Post by dms2871 » Sun Sep 18, 2011 10:21 am

I'm going to be primarily using it for street use but when I need to race it, I want it to be there

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Re: Differential gears limited slip to posi traction

#6 Post by Craig W. » Sun Sep 18, 2011 1:02 pm

I'd probably lean toward the Auburn or Tru Trac. Not sure what power level the Tru Trac is good for, so you'd want to read up on them first.
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Re: Differential gears limited slip to posi traction

#7 Post by chpcamaro » Sun Sep 18, 2011 10:48 pm

i would with out a doubt stay away from the detroit locker they are great for off road trucks but drag cars and street car no way jose unless you want nothing but problems ask wikd69(harry) ask him if he will ever use a locker again it cost him alot of suspension parts either go a posi or a spool. the eaton true trac or auburn is ok unless your putting alot of power through it well thats my 2 cents :smt003

also look at c clip eliminators also

oops i put the or in the wrong place but fixed now
Last edited by chpcamaro on Wed Sep 21, 2011 10:23 am, edited 2 times in total.
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Re: Differential gears limited slip to posi traction

#8 Post by dms2871 » Sun Sep 18, 2011 11:37 pm

so far my mind is set on a th350 and 435hp i know that has some factor in it too rear tires are 28x13.50x15 mickey thompson et street

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Re: Differential gears limited slip to posi traction

#9 Post by Craig W. » Mon Sep 19, 2011 6:06 pm

Maybe its the small slicks that let mine live, but I've had a detroit locker in my car for years. Its probably 8 years old, maybe older. Its never given a problem.
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Re: Differential gears limited slip to posi traction

#10 Post by Craig W. » Mon Sep 19, 2011 6:10 pm

Clutch style posi units haven't worked that well for me. Burned up two sets of clutches in the Nova before going to the Detroit Locker and after just a few trips to the track, the posi in my Firehawk isn't so positive anymore.

I hear the Pro version of the Auburn holds up pretty well.
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Re: Differential gears limited slip to posi traction

#11 Post by chpcamaro » Mon Sep 19, 2011 9:36 pm

do you use a trans brake craig ever one that i know using a transbrake has i fun ride befor the locker locks and then again maybe it is the small tire due to the less roll up it engages quicker i from what i have seen happen has been with no less then a 29.5 or bigger tire and that may be the factor
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Re: Differential gears limited slip to posi traction

#12 Post by Craig W. » Tue Sep 20, 2011 5:41 pm

Yes, I've had a transbrake in the car for 7-8 years. Almost as long as I've had the Detroit Locker.

Maybe its my habit of taking all the slack out of the entire car before going on the brake. I load it against the brakes just slightly as I'm staging. I don't want to use up any of the suspension travel but I think the car reacts quicker and its easier on parts if I go into the beams at about 2000 rpm.
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Re: Differential gears limited slip to posi traction

#13 Post by dms2871 » Tue Sep 20, 2011 7:41 pm

ok im confused now is the aburn a true track ??? or true track a difrent brand? i dont think they come with the gears allready installed

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Re: Differential gears limited slip to posi traction

#14 Post by dms2871 » Tue Sep 20, 2011 7:49 pm

what about this one?


Brand


Moser Engineering



Manufacturer's Part Number


542052



Part Type


Differential Carriers



Product Line


Moser Engineering Auburn Pro Series Limited Slip Differentials



Summit Racing Part Number


MSR-542052









Aftermarket Carrier Style


Limited slip



Cover Bolts


10



Axle Shaft Spline Quantity


30



Manufacturer of Axle


GM



Carrier Material


Steel



Quantity


Sold individually.



Notes


Includes bearings.








If you are looking for a stronger replacement for your standard differential, Moser Engineering Auburn Pro Series limited slip differentials are the answer. Available for most popular rear differentials, they are designed to provide more torque and faster engagement for controlled power transfer and quicker reaction to changing load conditions. Whether you're building a street vehicle or an all-out race vehicle, these Moser Engineering Auburn Pro Series limited slip differentials add reliability and consistency to your drivetrain.

Warranty

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Re: Differential gears limited slip to posi traction

#15 Post by Craig W. » Tue Sep 20, 2011 8:01 pm

True Trac is made by Eaton.

Auburn is a separate brand, which may have been bought out by Moser from the looks of the Summit ad you posted. The Pro Series Auburn should serve you well.

None of them come with gears installed.

You'll need a shim/installation kit as well. It'll come with shims, bearings, a new pinion nut, seal, gear marking compound, etc.
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