Need a posi-traction expert in St. Louis

[wes edwards]

Hello,

I need a referal for a local expert. My 1978 Corvette has developed a "posi-hammer" problem. I'm in West County St. Louis and would like to find someone to take a look at the car.

Thanks in advance for your replies.

[Joe C.]

Re: Need a posi-traction expert in St. Louis

Wayne,

Don't jump the gun! Have you changed the diff lube, and if so did you add 4-8 oz. of friction modifyer to the 80W-90? Have you driven the car in "figure-8's" to distribute the new lube between the clutch packs?

Joe

[Bernard M.]

Re: Need a posi-traction expert in St. Louis

Doug Johnson, Maryland Heights (314) 469-7223 (near Creve Coeur Park).

[wes edwards]

Re: Need a posi-traction expert in St. Louis

Joe,

Yes, changing the fluid and adding the posi-additive helped a little.
Did the figure 8 step as well.
Still has the problem when the mixture warms up after about 10 minutes of driving.

Thanks for your comments.

Wes

[Michael H.]

Re: Need a posi-traction expert in St. Louis

Wes,

There have been quite a few posts on this issue lately and several folks have stated that more than one bottle of the GM additive was required to correct the problem. I'm in the middle of the same exact problem with my 66. I've added one 4oz bottle and the condition did improve slightly but it definitely didn't go away. I'll be adding the 2nd bottle later this evening and will report tomorrow on the results.

[wes edwards]

Re: Need a posi-traction expert in St. Louis

Thanks Michael,

I've heard the "second bottle" theory too and am anxious to hear the results. Good luck!

Wes

[Joe C.]

Re: Need a posi-traction expert in St. Louis

Wes,

Sorry for calling you "Wayne" but one cannot edit posts here.......not important really, right.
Here is a case in point:

My 1965 Corvette, after I set up the clutch packs, displays nominal limited-slip clutch action after adding only one 4 ounce bottle of Castrol Friction Modifyer. It takes about 90 ft-lbs to break the clutches loose, with a breaker bar, with no chatter. Car lays down two distinct stripes on a holeshot. Diff is quiet, with no whine, chatter, or thump.

I do not know the history of your car. What is the mileage? Did you recently acquire it? Was it abused before you bought it?

THE BOTTOM LINE IS: If you have added at least 4 oz, but less than 8 oz of friction modifyer, and you still experience clutch chatter, then you should look into the possibility of damaged clutch discs in yout posi unit.

Joe

[wes edwards]

Re: Need a posi-traction expert in St. Louis

Joe,

The car was totally neglected for at least three and probably 5 years.
Sat without ever being started or moved.
It shows 59,500 miles. I've had two mechanics inform me they think it's accurate.
Bought it cheap and started the restoration in June 2005.
After ten minutes of the first "test drive" there was a significant and jolting noise coming from the rear end. Literally sounded like a sledgehammer was pounding on the rear wheels.

Had a mechanic drain and refill the lubrication adding one 4 ounce bottle of limited slip additive. The car was significantly better but I still noticed a slight noise. It's now 9 months later. The noise is back at probably 50% of the original problem.

It certainly wouldn't be a problem to add another 4 ounce bottle. Just looking for expertise and advice right now.

Thanks for reading.

Wes