Clutch packs "popping".......

[Chas]

We had a new rear end installed in 2004 and it has been making a popping sound at slow speed , usually in a turn around or stiff curve.
I was told it should fade with time and it has gotten better but not enough.
Is there anything I can do to help lube them better or such? Any opinions gang?
Thanks in advance, Chas

 

[6 Shooter]

Chas - Did they say it would get better with age or with miles of smiles?

L8TR - D

 

[LLC5]

If the vehicle sits for a long time it is possible that the friction plates are not properly lubed. Do numerous figure eights in a safe place and see if it gets any better. A drain and refill with the proper fluid and additive (and numerous figure 8's after the fluid change) would also be a good idea.

 

[Hib Halverson]

I suspect your "new" rear end was either assembled improperly or has the wrong lubricant in it.

Is the axle new or rebuilt? If rebuilt, who rebulit it?

Also, what kind of lubricant is in it?

 

[Eddie 70]

I had a 79 at one time that did this. What I did was to pull all of the old fluid out of the diff that I could and filled it with some cheaper gear lube that I could find. I filled the diff with the cheap stuff and took my car out for a ride around the town making sure I turned a few corners and worked the lube in real good. I came home and pulled that fluid out and refilled with the cheap stuff again. I made the same loop a few more times with the cheap fluid. I came home and pulled that fluid out again. This time I filled the diff again with Mobil synthetic oil and a diff additive. I never had a problem with the chatter again from the rear of that vette. It was about a days work but I had plenty of time to play with the vette. You may not have to go to the extreme I did but just changing the fluid and adding a bottle of additive may take care of your problem and can be done with the car on jack stands. Be sure to get the car as level as you can when refilling the diff.

 

[Chas]

When it was disassembled I was told that one of the ring bolts had backed out and trashed the interior of the housing.
I purchased a rebuilt hog and mine was worthless for the core so it was a costly repair. The rear end I had was a 3:11 and I went up to a 3:55. I purchased it from a place in Indiana I think and had it sent to the shop to finish the job.
We did the figure 8 stuff and such that we were told to do at the time of the repair. It didn't make the sound right away, possibly a year later before hearing it. I guess I should have gone back to the shop but I became hesitant and just took advise from vette guys that it was rather common and would eventually work its way out.
I believe they did it right and used the right lube (sorry I don't know exactly what they used), I did some research into the shop, but not into the place I got it from.
It is just something I want to address if I can before the season gets rolling.
I do have a very good repair shop that opened 3 years ago and want to take it to him, he did a frame off on a "70 Vette and also did work for Carroll Shelby,showing me photos of them together and too boot he is also a registered Ferrari mechanic.
I have confidence in him to look at it, but I also respect the gang here for tech advice, I want to know what makes it do this and hope it can be remedied this spring.
Prior to that repair I had all of the U-joints replaced and last off season I overhauled my brake system including a new master cylinder.I also have a new rear leaf spring and all new shocks.
It rides like a dream and stops on a dime, it just makes that popping sound now and then.:bash

Dwayne, Its all about "smiles per gallon" buddy!

(Eddie, What kind of wheels are those? Very nice!)
Thanks guys, Chas

 

[TimAT]

Drain the rear end, refill with 2 bottles of GM's posi additive and top it off with Lucas 90w. Drive the figure 8's and I'll wager the noise will go away.

While it's in the air, check the side yokes for slop too.

 

[Eddie 70]

(Eddie, What kind of wheels are those? Very nice!)

Chas,
Those are the ever popular Torque Thrust II wheels. Mine just happen to be 15X8 version with the standard corvette offset.

Be sure to let us know how this turns out for you when you get it worked out.

 

[GTR1999]

I suspect your "new" rear end was either assembled improperly or has the wrong lubricant in it.

Is the axle new or rebuilt? If rebuilt, who rebulit it?

Also, what kind of lubricant is in it?

I believe Hib is correct. Corvette (eaton) posi hammer/chatter is common on production built and stock rebuild unit. It comes from the way the posi was setup. Yes the additive may solve the problem and I hope it does but the true cause is in the posi. The tolerance of 001-008 lash is too much and procedures used by a lot of places is sloppy at best. Today new loaded posi's have fiber clutches, heavy spring rates,and less clutches. They still hammer. Try 2 bottles of additive, that might work otherwise you either live with it or tune the posi.

I will say my tuned posi's do not hammer and out perform a stock setup. You can find the link to my threads on this here or on other forums. If not and you want it just PM me.

Good luck

 

[Hib Halverson]

GTR99 is right.

If the limited slip set-up is done right and the correct lube is used, they won't chatter. Problem is a lot of rebuilders are either unskilled or are too much in a hurry and, thus, don't get it right.

As for "additives", I think two bottles is too much.

Know the limited slip "additives" are "friction modifiers". They reduce noise and chatter by degrading limited slip clutch action...just what you don't want for best performance. With my own Vettes, I've never had a problem with limited slip chatter but I have experienced trouble with the limited slip clutches squealing...which is just a milder form of the problem that makes them chatter. My solution has always been to add only enough friction modifier to limit the noise to a subdued squeal when driving in tight circles. I believe that is the best compromise between a limited slip that has noise and chatter but really bites in a straight line when maximum torque is going to the tires and one which has it's limited slip action degraded quite a bit in the interest of no noise or chatter at all.

Also, I would not use "Lucas 90W" gear oil. It is questionable whether Lucas Oil makes a gear lube that is any better than other "premium" lubes and I think a 75W90 or an 80W90 makes more sense for a street driven vehicle.

I'd start with a lubricant change and, unless the facility which did your last rebuild added a drain plug, to acomplish that, you will have to siphon the existing lubricant out of the axle.

I'd refilll it with a premium brand of 75W90 or 80W90 GL5-rated gear lube, such as Valvoline. Then I'd road test the car by, first, driving it 10 miles to warm the axle lube, then driving in tight circles or figure 8s in a parking lot listening/feeling for noise or chatter. If you have loud squealing or chatter, add half a bottle of GM's limited slip additive and road test again. If the problem is still there, add the rest of the bottle and road test. If the noise/chatter still exists, then I'd take the rear end back to the guy who originally rebuilt it because a freshly rebuilt limited slip unit which exhibits no reduction in noise/chatter with a full bottle of additive was probably not rebuilt properly.

 

[KANE]

...Its all about "smiles per gallon"...

For sure, Chas! :cool