Is my traction lock burned out?

Tony8470

Registered User
I was stuck on the side of the driveway the other day and one wheel wouldn't keep traction because of the wet grass. Is this normal? I don't know much about traction lock but I just want to know if I burned it out, or it has been burned out because it wouldn't stop spinning.
 
Tony, please describe your observations more specifically.

Are you saying one of the wheels was on the wet grass, the other on the driveway, and you observed the one in the grass moving faster than the one on your driveway?

Which wheel was in the grass?
 
Sorry, I thought it was a skimpy question but I thought it was gonna be just as skimpy of an answer.

The whole car was in the grass, got in the car at 7 in the morning with dew on the grass. The part where my car was on, was at a downhill slant from driver to passenger side. As I started driving and the car slipped further sideways down the hill. Then I really started trying to get the car out of the predicament. But only one wheel was spinning and not taking me anywhere. It was like this for the whole time till I got out. The other wheel would just move with the car but it wouldnt put any power to the wet grass. I ended up putting newspaper under the spinning tire to eventually get out.

Should I just do a sweet burnout to test if the traction lock is still there?
 
Ok, I understand now.

What you are experiencing is normal.

Although the name of our differential implies that it is similar to the locking units used on off road vehicles, it is actually just Ford's name for a common limited slip differential similar to the Eaton Posi units used by GM. If you are aware of how an LSD works, you know about how the design of the clutch mechanism inside means that the differential will transfer as much power to the non-drive wheel as is required to operate the drive wheel under its current traction level.

Hence, If the drive wheel is on a very slippery surface such as ice or wet grass, it is not being 'loaded' by friction and takes only a little engine power to make it move quickly/easily. The differential will then only transfer this little bit of power required to spin the drive wheel to the non drive wheel. If the non drive wheel has enough traction to move the car, it turns out that this little bit of power being transfered from the drive wheel isn't enough to turn the non drive wheel.

Sometimes the differential will switch off between wheels in this manner, resulting in the uneven patches seen when spinning wheels on pavement. It usually goes from one side, then the other then back, and so on.

Hope that helps, let me know if I have overcomplicated things as I have a tendency to do that :D

Clutch-Type Limited Slip @ howstuffworks
 
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So what your saying is that the one wheel that is moving more than the other one needs force applied against it for the clutches to work? Since the spinning wheel had very little force against it the clutches couldn't engage?
 
Exactly, because of the nature of the clutch type LSD.

I don't know the mechanism well enough to tell you exactly whats going on, but without a load on that spinning wheel, the clutches will not engauge with enough force to turn the other one. This type of LSD is dependent on input torque, and it doesn't take much torque to turn a slipping wheel. In addition, the LSD will only transfer as much as 70% of the torque to the other wheel even when everything is optimal.

I am researching this currently, and if I find an answer, I will tell you why it works this way.
 
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The whole point of LSD is when one wheel doesn't have traction the other wheel will still get power. Now it will never get all the power, but how much it does get depends on how strong the clutches are. If both your rear wheels were in wet grass then they should have both been spinning. However, both wheels spinning in wet grass still won't have a whole lot of traction. Try doing a burnout on the street and you should have 2 equal tire marks. If there's only one then your LSD is worn out.
 
Unfortunately I havent been able to locate more information yet, but if the speed difference from one wheel to another is too great, the LSD will not transfer enough power to the other wheel.
 
See updated article I wrote. I have added rebuild part numbers to help. If your clutches are worn your limited slip will not function. Proper operation of the limited slip is one tire spins the other starts.

Limited Slip Tech Info
 
Great info Rich! Just one question-not all SC's come with trac-loc?How can I find out if I have one other than a burnout :D -I cant,my car is ALL apart.
 
Door jamb has a ax code which lists the gear and if it has limited slip. All 1989-1995 SC except 1994-1995 Automatics came with limited slip from the factory.
 
To help DigitalChaos out I'll try and interpret the HowStuffWorks explination:

The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches.

What that means is that it takes a specific amount of torque to overcome the clutch pressure to allow one wheel to spin. That torque is applied to the non-spinning wheel up to, and during the spin of the other wheel.

Thus on wet grass, with one wheel spinning, it's likely that the clutch pack is very worn out in the original posters case. Since the torque necessary to spin both wheels should be less than the torque required to overcome the pressure of the clutch pack. Thus both wheels should have spun if the clutch pack was operating properly.
 
Excellent, thanks for the info Mike. I was having trouble with that statement and couldn't find anything elsewhere to clarify the LSD's operation.

I do know the LSDs seem to make the car very resistant to fishtail in low traction if the wheels do spin!
 
so, lets say for example. one wheel was in the air and one wheel was on the ground. Without the traction lock, the wheel in the air would keep spinning and you would not go anywhere. But from what I'm getting is the wheel in the air should lock up and the other wheel should grip, making the car move?
 
I'm not sure if the wheel in the air would lock up, but the LSD should make the other wheel move.

I just thought I found something indicating that if the speed difference between the wheels was too much, then the LSD would not work. I can't confirm this though so it should be disregarded.
 
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There are different types of limited slip systems so don't get taken off track by discussions of a different system.

The Eaton system, specifically, uses the friction between the clutch packs, enforced by springs, to ensure that power is spread between the two wheels.

On an open differential, if you have one wheel in the air and apply power, the one that is off the ground will spin. On our vehicle, power will be applied to both wheels up until the torque applied is greater than the amount of torque the clutch pack can resist.

Eaton's site explains it well. Of note is that Eaton's design relies on input torque to increase the friction of the clutch pack. So it is possible to be in a situation where only one wheel spins in slipery conditions if the surface is slippery enough to not allow sufficient torque from the engine to be applied, but with sufficient grip to allow the one wheel to over come the preload friction of the clutches.

http://www.traction.eaton.com/prod3.htm
 
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