Bangkok Dean

Just wondering if my 63 vert has positraction from the factory?

Nowhere Man

No It was a option.

sshort67

The Corvette Black Book indicates 17,554 of 21,513 63's had positraction. I have at least two copies of the "Black Book", one at my favorite chair and another in the garage. It is my go to information source and is very reasonably priced. I do not care anything about the current year Corvette specifications but it is a cornucopia of knowledge.

DZAUTO

Beginning mid-year 1957 (late Dec 56), positraction became a regular production option all the way up through 1969. In 70, posi became standard.
There had been a tiny number of prototype/experimental posi units installed in 56 (such as the Sebring race cars) and VERY EARLY 57 cars, but they were NOT production posi rears.

bb62

Yes, it was an option, but it was required with certain powertrain combinations. Virtually all solid lifter engines required positraction as well as other engines such as the 350HP 327.

gbvette62

All 63-67 327's (even fuelies) came with an open rear as standard equipment.

The 65 350 horse came with an open 3.70:1, and Positraction was optional. In 66, the 327/350 came with an open 3.36:1 with the wide ratio trans, and an open 3.70:1 with the close ratio 4 speed. Both rears were available with Posi as an option.

The only engines that required Positraction were the 65 396, and the 66-67 427's.

Most 63-67 optional ratios required Positraction.

Patrick03

Just light them up and see if you leave two black streaks. Pretty simple to confirm if you have posi or not.

tfiorino

How can I tell if my 65 convertible with a 327/300 has positraction

Nowhere Man

welcome but instead of bringing this old thread back to life you should start a new one. One way to check is to raise the tires off the ground by the trailing arms and turn a tire. If both go it’s a posi. If you turn one and the other one does not move it’s a open. If you want to have fun drop the clutch after you rev the engine up and see how many tire tracks you leave. You can also check the suffix code stamped on the bottom of the rear end and check back.

tfiorino

Thank you so much Sir. I am new to this forum. How do I start a new post please? I had a 65 convertible back in the 70's but sold it regrettably. Just purchased another one. While I have you sir, please remind me what the 2 black pull ***** are for under the steering wheel. Thanks again !!!

jwindarwin

Sounds like the fresh air pulls,,,,,,left/right

Nowhere Man

on the top of the page there is a box that says new thread Click that use a relative thread title that pertains to your question and ask away. As said above those two ***** are for the kick panel fresh air vents. I would suggest you go to your local repro parts house like Paragon or Zip and buy a repro owners manual

L78

Jack the rear up, both tires off the ground and the car in gear ( or Park for an automatic) and the engine off. Parking brake off too.

With an open rear, if you rotate one tire one direction, the other tire will rotate in the opposite direction.

If you aren’t able to rotate the tires, the car has Positraction ( unless the posi unit is extremely worn).

Nowhere Man

you have to Jack it up the trailing arms if you leave them hang you will put the U joints in a bind where nothing will turn

L78

hmm.

I did not know this…

But…

I just checked my Corvette’s gear ratio and determined positraction around Thanksgiving. The car was in Jack stands under the frame only, And there was no bind. I actually turned the main driveshaft by hand while my daughter watched the tire ( chalk mark) to tell me when the tires made one full revolution…

there was no binding…

mine match the code and the tank sticker, but after 54+ years, you never know…





Hard to see, but the stands are under the frame and not the arms…

Easy Rhino

That's a nice looking '67.

Add these two things to whether or not one has a posi.

1 - Is the differential original to your 50 year old car?

2 - If so equipped originally, is it still working as a posi?