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Is my LSD normal?

3K views 20 replies 8 participants last post by  Rollin 
#1 ·
Hello,

A few question to show my ignorance :) When I do semi-hard U-turns in my XR6 the back tyres squeek (you know, slower version of doing a set), is this normal for a LSD.

And second, whenever I take off fast and I go to second gear (5spd manual of course).. no matter if I trying and slip the clutch a bit or do a snap shift, it always does a chirpy.

Is that normal? I just don't want to stuff my diff thats all :)

Thanks!!!
 
#2 ·
yep, thats normal
the idea of the LSD is to give positive traction to both wheels, so when you are turning "fast" the diff thinks that one wheel is spinning(due to the turning circles of each wheel being a different size), and it locks up, giving you the slight wheel spin on the inside wheel
you only need to worry if the inside wheel locks up on slow cornering
 
#3 ·
I showed a mechanic (apprentice) and he got me to hold one wheel while he turned the other and declared the diff is locked (?) and said the oil needs changing to.

I'll be annoyed if thats the case, I'm not sure what it all means when the diffs locked.. does that mean its stuffed? :(
 
#4 ·
Dunno about having an LSD lock on you, more likely it would stop locking and slip more.

Mine shudders when you give it light throttle round a u turn, intead of spinning it goes ch ch ch ch ch and gets faster as the speed rises, alternately it just spins along with the other wheel and you know what happens then :driver:
 
#5 ·
it should be hard to turn the rear wheels independent of one another, ie hold one and try to turn the other with your hands, thats the whole point of them.

if its not possible at all (it should be pretty damn hard but) then its possible that bad things have happened in your diff.

if you can do a very slow full lock U turn and the tyres do not skip then its all good.
 
#6 ·
Well, I did two slow U-turn tests. One the wheel chirped and the other it didn't.

I should just take it to a proper diff place and ask them to have a quick look.

On a side note (I may start a new thread asking this) but what diff oil should I use in the EL XR LSD diffs?

I checked the manual and I can't find the ones it mentions anywhere.
 
#11 ·
85/140 sounds like a normal diff oil, not LSD oil. If you put normal oil in it, you will stuff it up.
 
#12 ·
Diff

From the sounds of things you diff sounds fine anyway so why bother changing the oil in it, unless its done a lot of km's. The LSD's used in these cars is a cone style, very similar to a Locker and it basically does that, it locks. You shouldn't be able to turn one wheel and hold the other, as someone has previously stated they are not supposed to turn free of each other. My EA Fairmont Ghia does exactly the same thing, you do a u turn and it skips one tyre, i changed the oil in it and it stayed exactly the same, the only thing i have found that makes a difference is too put on different tyres.

Another thing you can do is go in a big parking lot and do figure 8's, which will lossen up the diff, just nice and slow so that the wheels grip and turn the clutches. Althou i don't recommend doing this as it does where out your diff centre. but a little won't hurt it, and it might be enough to stop it.
 
#14 ·
The oil is normally pretty gluggy and is a very dark colour, it smells really bad too, it is like this straight out of the container. Being LSD it should be a dark green nearly black colour. normal engine oil is 20w-50 diff oil is in the 90w up. which is why it is so thick, 4.5times thicker than engine oil.
 
#16 ·
You shouldn't be able to turn one wheel and hold the other, as someone has previously stated they are not supposed to turn free of each other.
LSD means "Limited Slip Diff" not "No Slip Diff" if its not possible to spin one wheel independant of the other with an LSD then why bother having it? its a hell of a lot easier and cheaper to make a spool than an LSD setup.

the correct diff oil is LS 90 as per the book, i have LSX 90 in mine and it quietened it down a lot and it grabs less, the diff guy put 85/140 in it which is no good.

get them to change the oil at the 100k service, its good preventative maintenence.
 
#17 ·
Yes but an LSD will turn but it takes a lot more than two people holding each wheel. You should not be able to hold one wheel and turn the other unless your LSD centre is stuffed. When the car is on the road it is a lot different, an engine has an enourmous amount more touque than any person has and the road grips a lot more than any person can hold a tyre, which the grip will equal enough power to be able to turn the LSD centre.

You can test an LSD with a touque wrench by lifting one wheel off the ground, putting transmission in neutral, attaching the touque wrench at 3 o'clock on the wheel nut closests to 3o'clock position, move the touque wrench back and forth in each direction until a consistent reading in the 3 o'clock position is obtained, if it is below 27ft lb, or 36Nm then you need to reco your diff centre. If it is above then the diff centre is ok!
 
#18 ·
i think you might be a little off in your specs there - everywhere i have read is between 90 and 110Nm, which is well within the capabilities of even one human being of small stature, and 36Nm can be applied easily through a 1/2" drive ratchet!

also, if you lift one wheel off the ground and put the car in neutral when you apply torque to move the wheel the car will try and drive off the stands...

the correct procedure is to raise both rear wheels off the ground and put the vehicle in park/1st with engine off, then check the torque required to 'break' the friction of the LSD and keep the wheel moving independant of the other, as i said above it should be about 90 to 110Nm (for a falcon LSD) if i recall correctly.
 
#20 ·
The figures i quoted where direct from the book, with the method of how to do it. I believe to break the lock you are actually looking up to 400nm of touque initially and then you should measure it, but anyway as i said the 36nm measurement was only stating that the diff would need to be reco'd if it was below this, not what it should actually read which would be far higher like the 110nm your talking about.
 
#21 ·
Nicko - how hard were you pressing the brakes? are both your rear callipers nice and free? how many people were in the car? was it the RHS wheel that went up in smoke or the left?

if you were really pressing the brakes and/or one of the callipers on the rear of your car are sticking, its possible that one side was grabbing the disc that hard it was negating the LSD action of the diff.

also, if you have passengers in the back of the car, its best to have them sit on the RHS, this will reduce the load on the slip limiting mechanism of your diff*

how many kays has the diff done, and how often do you smoke them up? if you do burnouts a lot, it puts massive stress on the LS mechanism and it wears out a lot quicker.

if you are going to bag em up on the spot, dont do it for long, and have the passengers sit on the RHS as i said.

*due to the direction the engine rotates (anti-clockwise when viewed from the drives seat) when you accelerate hard the torque-reaction tends to unload the RHS tyre, so it spins up first in an open diff. if you put more weight on the RHS it helps the diff to spin both wheels by giving the rear tyres more equal traction.
 
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