so is it normal? shouldn't the inside rotate just as much as the outside?

 

[QUOTE=Steven2k,Nov 2 2006, 10:36 PM] so is it normal?

 

The Torsen LSD was designed to allow limited slip between the rear wheels, but enough to go around corners.
When one wheel looses grip during accelerating the Torsen "locks" the two axles together with gears, using the rotational speed difference of the two axles as a locking force, so you still have drive pushing you forward.
Driving around tight corners, the rotational difference is "telling" the Torsen diff one wheel (the outside wheel) is slipping, because it is making relativly more revolutions, so it starts to "lock" the inside axle to the oustside axle to keep accelerating, but in reality the outside wheel isnt slipping.
Going around a corner the axles can't be locked otherwise you wouldn't be able to go around the corner at all (on a grippy road surface).

So what is the Torsen diff to do?
Lock because there is rotational speed difference?
Or not lock because you are going around a corner?

This "thinking-what-to-do" can be heared as "moaning and groaning"

 

What happens in the LSD when driving backwards? Once I had to back-up on a hill with one rear wheel on asphalt and the other on a sandy surface. When one wheel lost traction the sound from the LSD resembled more gearteeth grinding than 'moaning', not a very comforting sound

 

mbvt Posted on Nov 3 2006, 12:50 PM
It makes no difference.
The gears inside the Torsen turn the other way but the principle remains the same. That is the way I understand it.

On the final drive gears it does make a slight difference.
The nature of the hypoid gears makes the pinion gear push the ring gear away when driving forward (that is why Comptech adds an extra bearing cap ) and pushues itself in the main pinion bearing.
Driving backwards the ring gear want to pull the pinion towards itself, towards the centre and (if possible) pull the pinion gear a little out of the bearings.
In a really bad worn out diff with worn out bearings and not enough pre-load on the pinion bearings that could result in the ring gear damaging the pinion (and vice versa).
I'm not saying that happend in your case, but it is possible.


More likely this happened:
There (most likely) was a lot of rotational speed difference between the wheels.
The Torsen was locking the axles together and the friction plates, inside the Torsen housing, covered in oil, were working hard to make that happen and were making a "grinding" noise IMO.

When was the last time you changed the diff oil.. and what oil is in there now?

 

dunno really

Car is completely stock, 7 years and 5 days old. Is changing diff-oil part of the 'major' maintenance service? In that case it will be changed in about two weeks (90k km service).

Thanks

 

Just for my understanding, in the s2k there's the Torsen T-2 LSD, right? Does that have friction plates too? I though it was transferring torque from one side to the other using gears? I'm having a look in Torsens' T2 leaflet PDF but I haven't figured it all out yet

 

spitfire, thanks very much for a well explained diff/lsd operation!!

would also like to add, that the sounds only tend to occur when the diff is warmed up. not very noticeable when its cold(atleast 10 hours of not driving, very cold here in chicago).

 

I had the same sound at around 500 miles with my 05 AP2 (never noticed it on my older AP1). I heard it while I was very carefully observing the breakin period. It seemed to go away and I have not noticed it in the last 4k miles.

 

yeah, i would have to say it was more noticeable in its earlier miles, say 100-500 miles. i'm sitting at about 750 miles, and its definitley there, but not as loud.