1967 Corvette posi-traction axle issue

[James C.]

Hello all,

I have just acquired a 67' Coupe that has option G81 (positraction - 3:08). I have noticed that on turns that it has a noise coming from the rear end/differential area, etc., etc. The local Chevrolet Dealer mechanical technicians I have spoke with so far say it is the clutches in the differential that are causing this problem and recommend changing the differential fluid. They also mentioned receiving recent Service Bulletins on current-model Camaros apparently having the same condition, etc.

My question is: has anyone having a 67' with this option have any knowledge and/or experience they can pass on regarding this condition?

[Joe L.]

Re: 1967 Corvette posi-traction axle issue

Hello all,

I have just acquired a 67' Coupe that has option G81 (positraction - 3:08). I have noticed that on turns that it has a noise coming from the rear end/differential area, etc., etc. The local Chevrolet Dealer mechanical technicians I have spoke with so far say it is the clutches in the differential that are causing this problem and recommend changing the differential fluid. They also mentioned receiving recent Service Bulletins on current-model Camaros apparently having the same condition, etc.

My question is: has anyone having a 67' with this option have any knowledge and/or experience they can pass on regarding this condition?

James------

Try adding two 4 ounce bottles of GM #88900330, aka Delco 10-4003, additive.

[Leif A.]

Re: 1967 Corvette posi-traction axle issue

James,

Fairly common issue with these early posi differentials. Do as Joe has advised and then take your car to a large, empty parking lot and drive the car slowly in figure 8 patterns. This allows the additive to work it's way into the clutches in the posi unit. 99 times out of 100 this solves the sound you're hearing. By the way, welcome to the '67 club.

[James C.]

Re: 1967 Corvette posi-traction axle issue

Thanks Joe, I'll do just that.... Although it's in very good condition, I have no idea how long this vehicle was sitting in between drives, etc.

[James C.]

Re: 1967 Corvette posi-traction axle issue

Thanks Leif!

Somewhat similar to yours this car has C60, M20 STD 327, G81, A01, Y60, U69. It's black with black (STD) trim.

It now has a set of the N89 bolt-on wheels and Coker redline radials and Power Steering (i.e., possibly dealer installed back in the day - but who knows).... However, in looking at the "Tank Sticker" it shows no wheel or tire option so I can only assume it was built originally with (standard) 775x15 BSW tires and (standard) rally wheels. It's also an A. O. Smith body car.

[Gary R.]

Re: 1967 Corvette posi-traction axle issue

You may need 2 bottles of the GM additive. I recommend 2 on all the rebuilt diff's I build. I don't have proof but I suspect this isn't the same chemistry as the previous additives.