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How do you identify non VS posi-traction equipped trucks? Especially 1958 but all in general?

Jack the rear-end up and turn one of the wheels. If the other wheel turns the same direction it is posi. If it turns the opposite direction or not at all it is non-posi.

There was no Positraction option in '58. Positraction was first offered in Chevrolet trucks in '59.

On a truck that old, it is probable parts have been swapped around, may not have the original year part installed. My '54 GMC has some kind of oddball rear end, I havent even been able to identify it yet, but it still works, just a bit of gear whine.

hey good question.I have posi in my 49 chevy 1/2 ton torque tube.Ive been told by old timers,48/49 was the first years as a factory option? so i was told.I dont have the #'s of the rear end handy, but I'll post them soon as I'll have more ????'s about changeing gear ratio's in a posi torque tube rear end. any way GMCCAMARO are we talking GMC or Chevrolet in your 58? are you sure you dont have a hibred.

What does the VS stand for in the original post?

Friedgreentomaters has the test.

I have a couple of posi pumpkins that fit in my standard half ton H033 rear end. I installed one at the same time as I did my Napco upfit. They are a clutch pack type, so limited slip is a better term. I can't find any information about their original applications, though, as they are obviously not the Spicer that became a posi option for these trucks in '59. That's a whole different rear end.

VS (usually in itallics) means versus or in comparison.

There was never a torque tube posi option. Chevrolet didn't offer Positraction on any vehicle until '57 (Passenger and Corvette). Chevrolet trucks got it in '59, and did not use the HO33 axle. They used the Spicer 45 from the GMC. That was a 1 year only axle for Chevrolet, '60-'62, possibly some '63s, have the Positraction HO33.
Just to clear up some confusion, there was a mention of the Positraction axle being a clutch pack type, and is more of a "limited slip" rather than a "positrac". Positraction is just GMs brand name for a limited slip differential, there is no difference. Chrysler called the almost identical design Sure-Grip, IH also used it as Twin Grip. All basically the same design.

I recall Twin Grip as an AMC trade name. Anyone else?

There's Limited Slip in the Frod line.

Eaton had Gov-Loc.

But the Oldsmobile Smart Track was the one I couldn't figure out. The only thing I knew for sure is my wife didn't have to worry or wonder if she should be in four wheel drive or not. I tried to get that Bravada stuck one time and gave up.

seems so

Bill

You're correct. Got my trademarks mixed up.

Smart Trac is an all wheel drive system. GM used it in the Astro vans, too. It's a type of full time transfer case with a fluid clutch for splitting the power. The Quadra Trak in Jeeps works similarly. GMs Auto Trac is a modification of that system that incorporats a 2wd mode for feul economy.
The Eaton Gov-Loc is a gear type timited slip, and works differently from a clutch pack style. Eaton was also the manufacturer of the Positraction in cars from '57, trucks after '60.

Bill...thanks for confirming that. The funny thing is I'm getting to the age where I can remember things like that but can't tell you about last week. Only reason I remember it is that I worked at an AMC dealership in HS and made several trip to Kenosha driving one and towing another. And the V8 cars would scoot.

There are three basic designs of traction-equalizing differentials. All of them work the same way- - - -when one wheel tries to spin, the relative motion between the axles applies a set of clutches that locks the two axles together. The torque transfers to the axle with the better traction. The lockup system is either a set of multi-disc clutches, cone clutches, or a positive locking system known as "Detriot Locker" that engages a set of steel teeth for zero slip. DL's are NOISY! The teeth ratchet over each other in a power-off turn, and most drivers really don't like the noise. They work great in off-road situations, but they're not too popular for street use. The cone-clutch type of limited slip axle requires a special additive to the lube to keep the cones from chattering and grabbinbg in a power-off turn.
Jerry

There's a fourth type,or actually third, cause the cone clutch and multi plate are similar function. Its what used to be called a Dual Drive.It's a differential with spiral gears,no clutches or ratchets or typical spider gears.The military used them and now they are sold by the aftermarket to retro fit popular car differentials.

MY COUSIN VINNY

Mona Lisa Vito: The car that made these two, equal-length tire marks had positraction. You can't make those marks without positraction, which was not available on the '64 Buick Skylark!
Vinny Gambini: And why not? What is positraction?
Mona Lisa Vito: It's a limited slip differential which distributes power equally to both the right and left tires. The '64 Skylark had a regular differential, which, anyone who's been stuck in the mud in Alabama knows, you step on the gas, one tire spins, the other tire does nothing.
[the jury members nod, with murmurs of "yes," "that's right," etc]
Vinny Gambini: Is that it?
Mona Lisa Vito: No, there's more! You see? When the left tire mark goes up on the curb and the right tire mark stays flat and even? Well, the '64 Skylark had a solid rear axle, so when the left tire would go up on the curb, the right tire would tilt out and ride along its edge. But that didn't happen here. The tire mark stayed flat and even. This car had an independent rear suspension. Now, in the '60's, there were only two other cars made in America that had positraction, and independent rear suspension, and enough power to make these marks. One was the Corvette, which could never be confused with the Buick Skylark. The other had the same body length, height, width, weight, wheel base, and wheel track as the '64 Skylark, and that was the 1963 Pontiac Tempest.
Vinny Gambini: And because both cars were made by GM, were both cars available in metallic mint green paint?
Mona Lisa Vito: They were!
Vinny Gambini: Thank you, Ms. Vito. No more questions. Thank you very, very much.

very good Jim bow !!!!

I associate Twin Grip with AMC.