Limited Slip Differentials

[duncan]

My understanding is that the Limited Slip Differential changed on manual transmission cars in 1995.
It went from a Torque Control Differential to a Torque Reactive Differential.

So as Question 1, how do each of the set ups work?

Both comprise a set of wet stacked clutch plates that can lock together to lock the axles:
- the 1991-1994 cars have a straight tooth inner gear in the differential whilst,
- the 1995+ have a helical inner gear

Help me here but I’m assuming
- with the earlier & auto cars one axle spins up, the clutch plates heat up with the spinning until they expand and then lock up, if both axles rotate at the same speed their is no lock up.
- on the later manuals, the helical nature of the gear induces an axial loading and this pulls the plates together thus locking the pack, again if both axles rotate at the same speed their is no lock up. In addition, on over-run or slipping backwards (see below) the diff unlocks.


And as Question 2, and I appreciate that their may be a clue from the Limited in LSD, but, in either case can the axle be induced or tricked into locking?


I ask because when trying to drive my car (manual, 1995) in Sunday night’s snow I had great difficultly in getting and maintaining traction. Trying to move off on hills; low revs, trickle away and I stalled, more revs and I was spinning without traction, if I caught traction the car had a really heavy, dead throttle response (no increase in RPM with significant throttle depression but slowing and stalling without) and when moving I was getting some form of cycling / pulsing from the drive train.
No doubt those behind on the hill watching me saw tooth at 45 degrees across two lanes were amused but I wasn’t.
Admittedly the Advan AD08 tyres may have been sub-optimal for the situation.

[NSX 2000]

This may or may not answer either of your questions.
Do you have a TCS button near the instrument cluster? I know I do, and this may (I'm guessing) activate how much spinning one wheel is allowed to do before they both turn (spin). I know in some cases car manuals tell you turn TCS off when driving in snow or mud so that both wheels turn (spin) at the same time.

[duncan]

That’s a thought, pity I didn’t think of it at the time - but - I won’t go out to try it now.
I’ll have a read up.
Thanks.

[britlude]

if I caught traction the car had a really heavy, dead throttle response

sounds like TCS kicking in... it should be accompanied by a flashing TCS lamp on the dash, (in the rev counter i think)...

giving it more beans won't make any difference it'll still try to kill the engine power, it only 'ticks off' if you momentarily lift off the throttle and reapply....

(found this out when an abs sensor failed, i was turning tight out of a garage forecourt , the TCS was convinced the rear wheels were spinning and killed the power... as i was trying to pull away up a hill!... pretty awkward to lift off completely and re apply with someone close behind that accelerated better than me!)

[duncan]

I’ve had a read, page 146 and 147 of the handbook: there it notes
- that the TCS will brake a spinning wheel and will also reduce engine power. (I certain felt the reduced power, i.e the car would barely go uphill)
- that it can be switched off but only suggests that when the folding spare is used. (Logical as the spare is a different diameter to both the front and rear wheels)
I can’t see any suggestion for disabling it’s use in mud or snow. (Though I used to do that very thing with my AWD Audi TT and had forgotten)

SO THANKS Paul and Jonathan, yes, I should have tried switching the traction off: thinking it through, with one wheel spinning it should then provoke the LSD into locking, I’m not about to go out and try,
ANYWAY, as lesson learned, even after 18 years ownership, read the b****y instruction.

Any thoughts from anyone else?

[NZNick]

My car doesn’t have TCS, so I don’t know what I’m missing. Also, not had need to use the car in snow so far, so nothing to add, sorry.
Kaz has driven his car in snow previously, shod with AD08’s - braver man than me!

[Nick Graves]

AD08Rs hate being cold and have minimal tread - kudos that man!

At least it's a trad LSD - the Torsen one in the S2000 and 86 don't function if there is that big a difference in mu and it's fully open. With the engine at the wrong end, they're a bit hopeless.

The Leg End has a snow button that converts SH-AWD into boring AWD - just as well as its Yokos also dislike cold. You can imagine which one I choose to smoke around in...

[britlude]

at mot time when jacked up, and the man turns the back wheel, the other wheel has always turned the same way, regardless of speed... obviously this is with the turning input coming from a wheel, rather than the engine, so guessing i have a tight LSD then...

tho, in the recent snow and ice, i've had to knock mine out of drive (yes, auto, no, i don't care) in order for slow speed maneuverability as the LSD axle wants to push the car on in a straight line, regardless of steering lock....

in addition the TCS stops unexpected wheels spin by killing engine power. (i dont think it has the ability to talk to the abs and brake individual wheels accordingly, but i may be mistaken, mines is an early one, so maybe later ones got more sophisticated!)