VetteGoVroom82

What year was posi-traction on the C3s, and how exactly does it work?

-Paul
huskerpaulie@yahoo.com

fauxrs

To the best of my knowledge positraction has been available or standard on every C3 made.

A positraction unit is basicly the same as an open differential with the added difference of spring and clutch packs. These spring press the spiders against clutches which cause both wheels to spin at the same rate. The clutches only come into play when there is enough torque to overcome their friction.

A better explantation can be found at http://www.howstuffworks.com/differential6.htm

Allan71

As far as C3's go, only the 1968 and 1969 came standard with a non-posi Open rear end.

These are the only combinations that did not require you to order Posi, although you could if you wanted. Any other engine, tranny or axle ratio required that you order Posi. For 1970 and up, all Corvettes had Posi as standard equipment.


300hp.................3.36.............. 3-spd Manual
300hp.................3.36.............. 4-spd Wide Ratio
350hp.................3.36.............. 4-spd Wide Ratio
350hp.................3.70.............. 4-spd Close Ratio

bence13_33

Sorry if I seem to be getting off track, but when was positraction first available (as an option or standard) on the Corvette?

Allan71

Generally first available in 1957, but a few late 56's did have the new Posi units....

3.70, 4.11 or 4.56 ratios

Rockn-Roll

I had thought that the posi-traction standard in C3's was first available for the 1963...I don't have my book here to check it. From my point of view the posi-trac works by applying power to the wheels that grip, which is the opposite from a standard rear end which applies power to the wheels that slip. Which means it's much harder to get a corvette to burn rubber. One example is the movie Inner Space where Martin Short is driving a mustang and he peels out in it...the tell tale sign of a standard rear end is the single line of rubber while a corvette leaves two equally thick lines of rubber.

Jvette73

Allan71, when you think about it that would be cool in its own way. A 4spd vette with an open rear. That would be more ability to show off chirping gears. I saw a ***tang pull out of a street show one time and he musta squeeled "wheel" for 200feet. No way he had a posi. But it was cool for the show factor.

Jester69Stingray

Yea but its much cooler for the guy with the Vette with posi who gets 3 car lenghts on the mustang while hes spinning the tires. :chevy
:cool:

Jvette73

Jester, yur definatly right there, and I get the picture good. :cheers:

VetteGoVroom82

So, the positraction waits until you let off the gas (or does it just take away power from the rear wheels) and the wheels slow down and then grip the road, and then the posi-traction adds the power back to those wheels? Is that why there's two strips of rubber on the ground behind a 'Vette, rather than one? (One for the 1st spin, the space between the strips of rubber from when either the power was reduced, and the 2nd strip from when the wheels re-grip the road, and the hammer is dropped?) Please let me know if I'm misunderstanding exactly how the posi-traction works. Thanks!

-Paul

Jester69Stingray

Theres two strips because theres one from each tire. You can still smoke the tires with posi but its harder becuse you have to spin both wheels instead of just one. Im not sure exactly how the internals work though. :confused:

rainman69

The simple definition of what the posi clutching system does:

It transfers power to the wheel with more traction. It is called "limited slip" as opposed to "full locking." The reason for the limited slip definition is that as one wheel starts to slip, the clutching mechanism on that side disengages that side and that disengagement forces the power over to the wheel that still has traction. If that wheel starts to slip due to the increased power, its clutch lets go and the power transfers back and forth in this manner.

This is why you get the two stripes versus the one. Whereas one wheel spins the whole way with an open rear, both wheels are spinning some of the time with the limited slip "posi."

This is also why if you're in the car when I sidestep it at 2500, the car's rear end slides right, then left, then right...hooks up nice and GOES like a bat outta ... (And it makes a nice screeee sound, as you hear both wheels break loose). :smash:

(And both wheels break loose in the 1-2, 2-3, and 3-4 upshifts...) :lol:

Jvette73

On an open diff the power is delivered evenly to both rear wheels untill the momment that one of the wheels, (usually the right one) breaks loose. At that point, if you continue to deliver power with your foot, all of that power will be delivered to the spinning wheel. On a posi, the side gears in the diff, which are the ones splined onto the axels, are loaded with pressure against one another creating a locking effect of the two axels togeather. This delivers power to both wheels, even if one of them begins to spin. On a good posi, the clutches are tight enough to hold the axels togeatger as one on a straight hard launch, hence two patches, while providing just enough slip to allow the rear wheels to travel at different distances when cornering moderatly.

Limited slip or posi rear cars can be more dangerous in rainy conditions since the back of the car can come around when both rear wheels are spinning. Accelerating too much through a turn in slick conditions will spin you around real quick with a posi. Be careful and know what you have and how it will react.