lsd operation

hi,

I've been looking for a difinitive way to test the LSD on my GQ, but have found conflicting information. My diff has the LSD sticker on and both wheels turn the same way when off the ground and 1 is rotated. I've tried jacking up 1 wheel and trying to drive it off the jack, but the wheel in the air just spins. I tried applying some brakes, but it still just spins. Yet, I tried it on the road with one wheel in some really slippy mud and the other on gravel, it locked up so well that the tyre on gravel actually span as well as the one in the mud. I got out of the mud easily with road slicks and 2WD. Any ideas what's going on?

I've also order some redline 75W/140 (with the friction modifier already in) as I'm not sure what's in the diff currently.

cheers

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Originally Posted by boggy2006

hi,

I've been looking for a difinitive way to test the LSD on my GQ, but have found conflicting information. My diff has the LSD sticker on and both wheels turn the same way when off the ground and 1 is rotated. I've tried jacking up 1 wheel and trying to drive it off the jack, but the wheel in the air just spins. I tried applying some brakes, but it still just spins. Yet, I tried it on the road with one wheel in some really slippy mud and the other on gravel, it locked up so well that the tyre on gravel actually span as well as the one in the mud. I got out of the mud easily with road slicks and 2WD. Any ideas what's going on?

I've also order some redline 75W/140 (with the friction modifier already in) as I'm not sure what's in the diff currently.

cheers

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Definitely change the oil first mate to ensure it is LSD oil. Sounds like it is grabbing under load though - when you had it in the mud. Happy to be wrong (generally am) but I thought the LSD needed load to engage and hence the concept of just jacking it up and spinning the wheels is not an absolute failsafe test.

thanks, that's what I was thinking, but when off-roading under full articulation with a rear wheel off the ground, wouldn't you want it to lock up to transfer power to the wheel on the ground?

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Originally Posted by boggy2006

thanks, that's what I was thinking, but when off-roading under full articulation with a rear wheel off the ground, wouldn't you want it to lock up to transfer power to the wheel on the ground?

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It only does that partially though - hence the words "limited slip" - it's not a locker, and will only attempt to grab for a short period without traction. My meaning was I thought you have to test it under load, being load coming from the drive shaft - power/torque as such. Again, could be wrong, but not sure jacking it up gives it any "load" as such and it may just act as a fully open diff. Something to do with how the diff alters the torque being delivered to the wheels under load to ensure the wheel with traction can still keep spinning - but again, is limited so will eventually release and act like an open diff.

Tony, how did I go? Have I failed? Am I relegated to the back of the class again? LOL!!!

As a rule a good tight LSD would perform better than you described so im thinking it may need a freshen up & I have also been told that getting one wheel only spinning up can cause damage to the LSD as well & you should lift out when this is the case to prevent damage but Tony is more up to speed on these thing so I'd wait for him to post up some info for you before righting it off on what I've said.

found this;

To appreciate just how ‘limited’ the slip is, try the following test. With a vehicle fitted with a rear LSD, place an axle stand to lift one of its rear wheels off the ground and then chock both front wheels with a brick. The LSD will not provide enough torque to drive the vehicle over the brick (vehicle obviously in 2WD). If a diff lock was fitted then the vehicle would drive forward easily.

In many offroad circumstances the traction avaliable to the rear wheels is similair and the LSD can control any wheelspin. However as soon as there is a large difference in traction ie. one wheel off the ground, there is no way a LSD will have any beneficial effect

from here http://www.pps.net.au/4wdencounter/a...difflocks.html

so A++ for Bigrig and Patch!

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Originally Posted by boggy2006

so A++ for Bigrig and Patch!

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well that's a first!! Staying on topic as well!!!! LOL

Till now anyway ....

mine had has that problem now i know how to fix it thanks guys

From memory a nissan lsd requires about 17Nm to engage and it hold to a couple of hundred Nm. If you are having a problem with it disengaging you can also use the left foot break trick

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Originally Posted by Bigrig

Definitely change the oil first mate to ensure it is LSD oil. Sounds like it is grabbing under load though - when you had it in the mud. Happy to be wrong (generally am) but I thought the LSD needed load to engage and hence the concept of just jacking it up and spinning the wheels is not an absolute failsafe test.

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Ok off topic, have seen straight 140w recommended, what's the feeling here.

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Originally Posted by Robo

Ok off topic, have seen straight 140w recommended, what's the feeling here.

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Mines 75w145 Penrite LimSlip I think.

hummm I run 90w lsd oil for the GU - thort most ppl run 75w-140 if a lokka is fitted ?

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Originally Posted by Bigrig

Mines 75w145 Penrite LimSlip I think.

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I've looked at penrite cat some time back , think I recall penrite recommend straight 140w limslip.
that why I asked the ?

I run 85-140w in both ends front has an auto locker, rear lsd. I originally put the thicker oil in the rear to get rid of clutch chatter.

thats good to know that the LSD doesnt work if one tyre off the ground as i had this happen to me an thought my LSD was stuffed. so thanks guys.

Has anyone tried the engine oil flush trick in there LSD?

also, can someone explain why clutch packs would need load to function?