Testing limited slip differentials

Submitted: Sunday, Feb 26, 2006 at 14:35
ThreadID: 31175 Views:13452 Replies:5 FollowUps:7
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Greetings,

Discussion over a beer on the longevity of limited slip differentials led to the question how do you test if your LSD is working correctly. One suggestion was to jack up one rear wheel on a trolley jack and see if the other wheel would drive the vehicle forward or reverse. Did this and there was an attempt only to push the vehicle forward but the wheel off the ground spun.

Any suggestions

Redeye
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Reply By: Notso - Sunday, Feb 26, 2006 at 14:55

Sunday, Feb 26, 2006 at 14:55
Have a read of this article. From what he says yours seems to be "Working"

http://www.pps.net.au/4wdencounter/articles/difflocks.html
AnswerID: 157148

Reply By: Wayne (NSW) - Sunday, Feb 26, 2006 at 15:26

Sunday, Feb 26, 2006 at 15:26
Redeye,

I have heard about the drive of the jack method, not real keen on it.
The other way is to jack up both back wheels and turn just one. If the other back wheel turns in the opposite direction then it is a open diff or the LSD is not working. If the wheel turns in the same direction then there is some form of locking in the diff. If you get someone to try and hold the wheel while you try and turn the other it will give some indication on how well the LSD is working.

Wayne
AnswerID: 157153

Follow Up By: hl - Sunday, Feb 26, 2006 at 16:09

Sunday, Feb 26, 2006 at 16:09
Just jack up one rear wheel and leave the other on the ground. It should be very hard or impossible to turn the wheel by hand. LSD's do wear out and if you can turn the wheel fairly easily, then yours is.
Cheers
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FollowupID: 411384

Reply By: Exploder - Sunday, Feb 26, 2006 at 16:22

Sunday, Feb 26, 2006 at 16:22
1.Jack one rear wheel off the ground and grab a Torque wrench, you need to find out the Clutch load for the LSD (Call the manufacturer) for augments sake call it 20Ft/Lbs set the toque wrench and attach to a wheel nut and try to turn the wheel. If the wheel turns and the Toque wrench doesn’t click your LSD is worn or stuffed.

Or just try to turn the wheel that is jacked off the ground it should take a bit of effort to turn.

Alternately just pull a burnout on some gravel. LOL

AnswerID: 157161

Follow Up By: Exploder - Sunday, Feb 26, 2006 at 22:25

Sunday, Feb 26, 2006 at 22:25
Just thought I would practise what I preached, never having actually tested it my-self.

So I jacked the rear right tyre off the ground leaving the rear left tyre firmly on the pavement, put transmission in neutral with the handbrake off.

The Traction Loc LSD I have should need around 28 Ft/Lbs to overcome the Culches in the diff, So it was out with the Toque wrench set to 28Ft/Lbs and placed it on a wheel Lug nut on the right rear and tried to rotate the tyre sure enough the Toque wrench clicked at 28Ft/Lbs just before the right tyre over came the LSD clutch plates.


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FollowupID: 411467

Reply By: fisho64 - Sunday, Feb 26, 2006 at 16:27

Sunday, Feb 26, 2006 at 16:27
dont think that works with a LSD, only a locking one. LSD is just that-limited and needs torque to operate
AnswerID: 157163

Follow Up By: Member -Dodger - Sunday, Feb 26, 2006 at 16:55

Sunday, Feb 26, 2006 at 16:55
Fisho is correct, there has to be some torque on the lifted wheel to operate so put some friction on the spinning wheel and you will find that if the LSD is working then it will try to move fwd on the trolley jack.
In a situation in very slippery conditions it helps to have a notch or two on the hand brake to lock up the lsd so that some traction can be gained on both wheels, this only works when the handbrake is on the wheels not on the drive shaft as in a Nissan.
I used to have a handle on life, but it broke.

Cheers Dodg.

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FollowupID: 411391

Follow Up By: Exploder - Sunday, Feb 26, 2006 at 16:55

Sunday, Feb 26, 2006 at 16:55
I assume you were referring to my reply

A LSD is Limited in that it will allow limited slip between the wheels to a point.

A LSD will slip if one tire has no traction and the torque input coming down the driveshaft and the traction of the tires combined is more than the clutches can handle, it will go back to operating like an open differential and send the power to the wheel with the less traction.

This is essentially what you are testing by having one wheel off the ground and the other firmly on the ground and rotating the wheel that is in the air, the toque wrench set to the correct Factory Setting is measuring how much force is needed to overcome the culches in the LSD.
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Follow Up By: pjchris - Sunday, Feb 26, 2006 at 19:23

Sunday, Feb 26, 2006 at 19:23
Unless it's a Torsen Diff like the NM/NP Pajero where you must have some grip on both wheels for the diff to function. If one wheel has no grip at all it will, apparently, act like an open diff. Once the diff starts to bite, however, it will just keep gripping. There are NO clutches in a Torsen diff.

See Torsen diffs

Peter
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FollowupID: 411432

Follow Up By: dan01the01man01 - Sunday, Feb 26, 2006 at 20:28

Sunday, Feb 26, 2006 at 20:28
I have been told to ensure the LSD is working to drive it in 5 full left hand turns and then 5 right hand turns, this is to allow oil to get into the cluch system to check the LSD, also have tried the jack on one wheel, didn't move at all, stilll not sure if my LSD works.

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Follow Up By: fisho64 - Sunday, Feb 26, 2006 at 23:20

Sunday, Feb 26, 2006 at 23:20
exploder, dont know why but I actually hadnt read yours! But you are totally correct!
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FollowupID: 411487

Reply By: Utemad - Monday, Feb 27, 2006 at 17:51

Monday, Feb 27, 2006 at 17:51
I have used Exploders method many times. Not the techo one but the fun one.

Park on grass/gravel/sand, put the clutch in, rev it, let the clutch out. If you leave two lines then your LSD works.

The LSD in my Rodeo has never been worked on or replaced and it still works after 184k.
AnswerID: 157326

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