# posi traction



## Chris-Austria (Dec 23, 2010)

Hi!

I was asked how much my posi traciton "locks" (1-100%) but I cannot find any good Information. Are there different kinds of posi tractions for the GTO? And how does it work? With a clutch inside?
Only thing I know is that it's a stock unit and that both wheels burn rubber 

Chris


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## PontiacJim (Dec 29, 2012)

I am responding to this post, even tho a bit after the fact. There are an assortment of "posi traction" differentials based on the factory auto manufacturer and then the all the aftermarket offerings of which there are quite a number. To begin with, a posi that would offer 100% all the time would most likely be some type of an aftermarket "spool". It locks the 2 axles directly to the differential/ring gear. Used mostly in drag racing, but some guys do use them on the street. Very dangerous in the rain or poor roads, and hard on the drivetrain in corners as both wheels rotate at the same time when one needs to rotate faster than the other.

Pontiac, and GM cars had a "limited slip" posi differential in that the posi has several clutches and heavy springs. Limited Slip and positraction (posi) differentials are designed to "limit" the tendency of open differential to send power to a wheel that lacks traction and redirect the power to a degree to the other wheel of the axle. The Limited Slip and Positraction differential will send power to both wheels equally when traveling straight, however when one wheel spins due to a lack of traction, the differential will automatically provide torque to the other wheel with traction. Limited Slip and Positraction (posi) differentials limit the loss of torque to a slipping wheel through various mechanisms such as clutches, gears cones, and other methods dependant on the unit. The limited slip and positraction will not provide 100% lock up of the differential in extreme situations such as when a wheel completely looses traction. Limited Slip and Positraction (posi) differentials are recommended for daily driven vehicles. Eventually the clutches will wear out and need replacing.

A "Locker", as in the well known "Detroit Locker" is a locking differential that uses a mechanism that allows left and right wheels to "lock" relative to each other and turn at the same speed regardless of which axle has traction and regardless of how little traction a slipping wheel has. In this state, the axle acts more as a "Spool". This means traction can be sent to a wheel that may be planted firmly on the ground while the other wheel of the axle is completely off the ground. Lockers tend to create odd handling characteristics on the street as they lock and unlock and take some getting used to.

I did some researching into the various types of posi and locker differentials. I am building a high HP and torque Pontiac engine. I opted for an aftermarket 9" Ford fitted with the correct GM brackets so it would bolt in. Got the aftermarket 31 spline axles and large sized bearings. I am now putting together the differential rather than buy one already assembled - I like to do my own specs. The "posi/limited" style seemed to me like it would not hold up to my build and the "locker" was going to be too aggressive for a street car. So, I ran across the aftermarket Richmond PowerTrax "locker". I emailed the company to make sure the unit would hold up to the power I anticipate and the wide biting tires I will be using. I did not want something to blow up on a real hard burnout, nor did I want to throw my money away. They have 2 versions and I also wanted streetabilty versus the bad manners of a "locker". They advised that I purchase the Power-Traxx No-Slip locker as it would be no problem handling my engine/power combo and would give me the streetability I was looking for. I have purchased the unit, which is on a back order as of now, but think it will fit the bill. I am not endorsing this unit as I have no experience with it, just seems like a good choice all said and done. You can go to their website for more details. It is a simple bolt in unit that anyone with mechanical skills can do. I will be using a simple open carrier from a Ford 9" rear and slipping it in place. Don't need to buy a high dollar Ford posi rear section as you will be replacing it. As I recall, they do offer these for the GM products as well, but won't swear to it. Hope this helps a few of you.


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## Chris-Austria (Dec 23, 2010)

Thanks for the response.
So there are limited slip and locker differentials? Does my posi have a specified amount of lock-up like let's say 30% or is that something that only locker differentials offer?


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## Indetrucks (Apr 2, 2013)

What do these cars come with from the factory?
A GTO for example (66 -67)

If I recalls, the chevy supersport cars of the muscle era had posi if it was a 12-bolt rear end. And the 10 bolt rear ends had the old one-tire-fire.

Did most or all GTO's come with posi?


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## 68greengoat (Sep 15, 2005)

Open diffs were standard, Safe-T-Tracks were optional.


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## 68GTO4004Spd (Jun 19, 2008)

64 thru 69 had only the 8.2" 10 bolt available, and yes the "posi" was called Saf-T-Track by Pontiac. Here is a pic of the pumpkin cover.


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## BearGFR (Aug 25, 2008)

There's another option. Wavetrac - which is what I'm running in my Moser 9". Love it.
Wavetrac® Differential - A torque biasing differential with a difference

Bear


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## Rukee (Feb 8, 2007)

BearGFR said:


> There's another option. Wavetrac - which is what I'm running in my Moser 9". Love it.
> Wavetrac® Differential - A torque biasing differential with a difference
> 
> Bear


Very interesting.


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## Indetrucks (Apr 2, 2013)

68greengoat said:


> Open diffs were standard, Safe-T-Tracks were optional.


When I go look at a 67 GTO on Sat. what's the best way to tell if it's a Safe-T-track rear end?

Other than doing a burn out or jacking up the rear to spin the wheels.


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## 68greengoat (Sep 15, 2005)

Those are the best ways. Of course, lighting them up being the most fun. The owner may not think so, however..... There are codes on the axle tubes, however, you don't know if the carrier/gears were changed. May have an LSD in a non LSD housing too.


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