Limite Slip Problems?

[LarryBible]

Well, I put an odd tire on the right rear. I used chalk marks to measure the rolling diameter of both tires, and they differed by about 3/8".

After driving about 800 miles on this Jerry Rig, it has gotten to a point that sometimes after making a turn, it seems to have drag like a brake is on, then it breaks loose and kind of shoots to the right.

I suppose a brake could be hanging, but I am suspicious that the limited slip is causing this.

I was not far from home last night and it really did it bad. You could really feel the loss of power. That tells me this is a lot of drag because there is so much power, that it would have to be a lot of drag to feel the engine tugging against it. This was after making a left hand turn at a stop sign onto a wide open two lane. Once it let loose the car darted to the right a little. When it has done this, it always darted to the right when it turned loose.

Questions:

Is 3/8" rolling diameter difference too much from side to side for the health of the limited slip diff?

Does this sound limited slip related?

Does it sound like it is the diff rather than ABS, or otherwise having a brake hanging?


I will check the brakes on the left side this weekend to see if there is a pad or two that have a lot of extra wear. And I went ahead and ordered another tire for the rear so that they will more exactly match. I don't know if 3/8" rolling dia. difference is too much, but I don't want to take a chance on ruining the differential. Then again, if I do, maybe I can gear it a little more aggressively at the same time.

Thanks for sharing your experiences with this,

 

[Mikebmab]

Doc
try moving front tires to the back, if they are identical and go for a drive... Steering will be a little touchy I would imagine but should tell the tale for rear end/ diff/ brake problems...
Keep us informed.

Mike

 

[Vettelt193]

Does it happen after the same kind of turn... ie right or left? or does it not matter which way? If it is the limited slip rear having troubles with the difference then it should only do it when turing right or left, not both.

 

[LarryBible]

I think it happens turning either direction. The time I remember for sure was last night and it was after a hard left turn.

I'm not going to drive it again until I get the matching tire on the left rear. I ordered it this morning and it should come in Friday. I will put it on Friday night or Saturday morning and drive it to town for annual inspection. I should know more then.

Thanks for the responses,

 

[jstkrsn]

The one time I had trouble with limited slip, the car would shudder when I backed up and turned at the same time. I changed the gear oil and added the shark oil or what ever it is for the limited slip and it went away. Easy fix, but it drove me nuts until I figured out what it was.

 

[Rowdy1]

Tire Size

I don't know if I still have the magazine, but a couple years ago there was an article about a guy that smoked his posi by running two different size tires. It's the same theory with a 4X4 vehicle, I wouldn't drive it until you match them up again.

 

[Mad-Mic]

Larry,

i had a rr caliber lock up on my rr disc in my camaro once or twice was after i braked and held my foot on the braked at a stop light so they can stick. what usually does this is the o-ring around the piston leaks and gums up. check your brake fluid level. the night it did it i pulled it into a store parking lot and looked at it and it was glowing! not good! but i can imagine if your tire diameter is larger on one side than the other it will spin that axle faster than the other also like when you go around turns but on straightaways. i hope its just something simple and not the rear going up.

hope this helps,
Mic

 

[LarryBible]

The more I think about it, the more I suspect this as a brake problem. The tire should be here today, so I might as well mount and balance it. While the wheel is off I will check the pads closely, if they look okay, I will pull the left front and check those pads.

The brake parts on these cars are way too expensive to take chances with. I have flushed the brakes about every two years since I've had the car, but things can still happen.

Thanks for the respones,

 

[LarryBible]

Mad-Mic,

When you experienced your brake problem, would it drag on one side and then SUDDENLY turn loose?

Everyone,

Thanks for the responses regarding different tire diameters. In the factory manual, they go into detail including equal treadwear and tire pressure on the rear tires. I've always known not to run different size tires, even on a standard differential, but GM is particularly cautionary in the manual.

I got my matching tire in today and mounted and balanced it tonight. I am really pleased that I got an old tire machine and poured a pad behind my shop to mount it. I also bought a used Coats 1001 computer balancer so that I can always see that my wheels are Dynamically Balanced. I got tired of fighting the tire stores to get them done right.

Now I get to drive it in the morning I will report back.

Thanks for all the responses,

 

[rrubel]

Larry, what's "dynamic balancing" and how does it differ from regular balancing?

Thanks...
[RICHR]

 

[Mad-Mic]

Mad-Mic,

When you experienced your brake problem, would it drag on one side and then SUDDENLY turn loose?

yeah it did let loose i didn't notice any leakage and it only did it once or twice i noticed it at night it was glowing red i've replaced both front calipers on the cammy not the backs yet i'm actually gonna replace all 4 with new lines and new mastercylinder and brake booster wilth upgrades.

 

[LarryBible]

rrubel,

Dynamic balancing describes balancing the wheel from side to side as well as static balance. Static balance can be done on a bubble balancer, it only balances the wheel such that it does not bounce up and down. When you allow them to balance your wheels with weights only on the inside, they are static balancing and the wheel will indeed not hop up and down.

By static balancing, however, the dynamic balance is aggravated because all weight is added on the inside which almost always ruins the side to side balance. If a wheel is dynamically imbalanced it will "wobble." The Vette tires being as wide as they are, are really susceptible to this wobbling, and the Vette suspension, as most modern car suspensions, are susceptible to this wobble.

The best solution if you don't want a weight on the outer lip is to use tape weights just behind the spokes of the wheel. To clear the caliper, you need to use thin tape weights. You can buy them that are .100" thick, they will clear on the C4.

To learn much more about wheel balancing, go to www.gsp9700.com Click around in there and read the technical informatiion. They have diagrams to make it easier to understand than are my words.


It rained yesterday, which is quite uncommon in Texas, in mid August so I didn't drive the Vette. I will be out of town all week, so I hope to check it next weekend, for those interested.

Have a great day,

 

[rrubel]

Thanks for the explanation, Larry. I've been taking the Vette to NTW (though I may stop, for various reasons) after having Sears really foul up a balancing. NTW appears to use the thin tape weights and they're fairly close to the spokes, though not right against it. NTW is one of the places listed by Hunter as using the 9700 (I checked after another recent thread) though I've never looked to see if my local one does have that unit.

Sears, btw, used tape AND lip weights, and used lip weights to counterbalance OTHER lip weights. While I realize they're the same parent company as NTW, so far I've been less than impressed with their personnel.
[RICHR]

 

[LarryBible]

I mounted and balanced the new tire on the left rear a little over a week ago and finally got to drive it yesterday. I only drove it about 40 miles and everything was well.

When I was having the problem before it was during 90 mile runs in the Texas afternoon heat. I will not feel that all's well until I've driven it again under these conditions.

I still worry that there are brake problems to be dealt with.

Thanks for all the suggestions and comments.

Have a great day,

 

[vigman]

Larry just for giggles

You might want to drain the rear end out and replace the Posi fluid....


ONLY USE THE GM OIL & ADDITIVE..... It couldn't hurt... and your rear end will thank you for it.


Vig!

 

[LarryBible]

Well, good news is that I drove the Vette to the office yesterday. This would probably be no big deal for most of you, but my office is an 89 mile drive one way. About twenty miles of that one way trip is winding, hilly famr roads on which I literally know every bump and poorly banked turn. It's an absolute ball to drive on this section of road.

Bad news is, even with the exact same tires on eac rear wheel, the problem I described earlier in the thread still remains, among a few others.

It happened once after running straight on the wide two lane portion of my drive, in the afternoon after a thorough warm up in 97 degree weather. I immediately pulled over and felt the wheels and looked at the rotors to see if there was one that was hotter than the others. I could not find one, they were all very warm to the touch, as you would expect.

Vigman,

I looked to change the rear axle lube awhile back and if I remember correctly, I had a tough time figuring out how to drain it. There is no drain plug, and if I remember correctly the mounting makes it difficult to remove the cover. Any suggestions? I have the additive and top quality rear axle grease and a pump on the bucket to get it in.

Have a great day,

PS, I had repaired an A/C leak, pumped down and recharged. I converted to r134 last year. I evacuated, charged and I had already adjusted the pressure cycling switch to cut off at about 21.5 on the low side for use with r134a. Even in near 100 degree weather yesterday I could've made ice cubes. The vent temp got to 41 degrees. The later C4's convert quite well to r134a. I would not convert an earlier R4 compressor system to 134, but the Nippon compressor works out very well when properly converted. LB

 

[vigman]

Da Rear

So .. they have a boat sump hand pump they use to drain the oil..

They meaning Jiffy Lube & such places...

On the side of the Diff there IS a fill hole.
( pass side )

You stick the hose in there.. and pump all the ICK out... now you cant get it all, but you do get 90%.

And pour the new lube in

PUT THE GM ADDITIVE IN FIRST!


Vig!