Earlier today I did a burnout and found that instead of 2 strips of rubber down the road, I was left with one dorky strip. I thought that the limiter slip dif. took care of that to make sure the tire with the least traction would not just spin.

So what did I do...tried again and still only one strip of rubber.

What concerns me is about a month ago both tires would spin.

My question:
Is there something wrong my dif. or something or is it normal for it to do this sometimes?

 

Well, it could be a few things, how many miles do you have on your truck? rear Limited slips do wear out due to clutches being the means of locking the two tires from spinning independently. They also have their limits, and can be "overpowered" making them slip. Was the road crowned? If the road was crowned or you weren't straight then the limited slip will disengage causing one tire to spin. I'd change your rear diff fluid, add the friction modifier, drive it around for a few days, and then try it again. If that doesn't work then your limited slip unit is probably just worn out. You can also jack up the truck and have someone hold one tire while you spin the other, it should be difficult to turn or wont turn at all, just make sure you're in neutral at the trans. It depends on how the unit works, too. Some of them free-wheel until torque is applied. Hmm, hope I helped some. Let me know what you found out. Posi-units are such a mystery sometimes.

 

A LS Dif, is just that, it is not a Posi Lock. I guess with the right amount of HP aplied in the right way, you could peg leg it. I have a '95 8.8, it does not have a LS Dif, but it will break em both loss under more power, but if I were just to brake tourq, I just one wheel wonder a peg leg all the way. I think a LS dif woulb be oposite. I would get to some gravel and just giv it a bit of throtle, if both tires brake, I would not imagine you have any dmg to the diff. But if it is under warenty, take it in, you may have some clutch plates going bad for some reason. Buy a locker!

 

Change your fluidin the rear end and you'll be good to go.

Unless the rear end is making noise, typically a fluid change will solve your problem.

 

Sounds like your limited slip is toasted. In general the factor ford units are a weak link in the rearend. In theroy the more power you put to the LS the tighter is should lock forcing both tires to spin. a dry burnout is the worst thing you can do for a LS. The ford units have a funny way of dying, one day they will work and the next they won't and never will again. I replaced two on my truck, 'until I got smart' I bough an EATON POSI. Buy an eaton.

 

The Eaton posi is GARBAGE. You're better off with a stock unit. There are several people on here that will concure. Sal is one of them.

 

HI!... I can't beleive someone suggest the EATON posi for the 9.75 rearend. The EATON unit for the 9.75 is the biggest piece of JUNK out there. Read around, just about everyone breaks it. It's half the size of the factory unit. EATON = CRAPOLA!!!!!!

 

I've got almost 80k miles on the truck. NO Warrenty

First burnout was on a relativly rough worn road the second was on a flat smooth road.

I am the second owner and have no idea if the dif. fluid has ever been changed. So, I'm going to go ahead and change the dif. fluid tomorrow and see how that goes. Any recomendations on what fluid to use or is it all the same stuff?

Also, not sure if this is a dumb question but what is a locker?

Thanks for the help guys.

 

HI!... I'm running REDLINE synthetic rearend fluid. It has friction modifier already in it, but my rearend builder suggested to also add the FORD friction modifier to it anyway. Been 2 years now since the rebuild and works great. I change my rear fluid once a year no matter what the milage is.

 

Do auto stores carry the ford stuff too? Everything from ford seems to be over priced.

 

Changing the fluid will solve your problem.

Add the oil and the friction modifier!

I only use FORD modifier with synthetic fluid.

 

Alright thanks for all you guys help. Glad to see this is most likely nothing major.

 

I havent tried an Eaton in a 9.75,but the Eaton for the 8.8 works great.

Change the dif. fluid and go from there,if that dont work....

 

The Key with the eaton is to set the preload right on the spider gears and select the correct springs for the clutch pack.

The eaton is the strongest 'posi' on the market and the most reliable. I run one in a Ford f-350, after trashing 2 ford units. I alson run one in a 95 Impaala SS with over 700 rwhp and I have never had any rpoblem with the eaton. It all comes down to the setup.