Diff chat: mech LSDs

[mist]

Jay - stock item is a viscous LSD. Aftermarket ones (CUSCO, NISMO, KaaZ, etc) are also LSDs, but they are mechanical and utilise clutch plates. I don't think anyone seriously wants to drive around with a fully locked diff...

I think 2-way LSDs will provide the most consistent reaction when the tail steps out of line as the locking action remains the same off or on throttle. 1.5-way can be a bit more snappy, as the locking action when off-throttle is half of what it was on-throttle. I run a 2-way LSD in my car for circuit / drift use. It was quieter when I had a heavy duty clutch, but bites a lot harder now and is noiser with my button clutch. Usually get confused onlookers wondering what is wrong with my car when the LSD does it thing @ parking speeds, but that's all.

[Steve]

Duncan, you ask why anyone would want anything but a 1 way - well I definately prefer a 1.5 or 2way. With a 1 way, if you get oversteer and back off, your back end can whip around really hard, throwing the rear in the opposite direction. A 2 way will not do this, and a 1.5 wont either.

2 way (according to sydneykid) has an advantage if trail braking into corners. I dont do this often, but if you do get a corner come up unexpectedly (it has happened to me) and you are hard on the brakes into the corner, the weight can lift off the inside rear tyre resulting in sudden hard oversteer (the rear wheels are not working together, power goes to the wheel with the least resistance) - which can be pretty hard to catch. So there is a benefit in that it keeps power to both wheels.

Stock nissan skyline diff is a LSD, which stands for limited slip diff. There are many types of LSD, the stock one is viscous - it has oil in it. This will allow one wheel to spin before the diff locks, when both wheels will spin. Viscous diffs can be a little unpredictable, esp when they get older. Open wheeling, then if the wheels lock sometimes kicking the back end out unpredictably and wider/quicker than a mechanical LSD.

Mechanical LSD uses plates like clutches. when the plates are pushed together, the rears lock. 1 way will lock only under accelleration, not under decelleration. 1.5 will lock under accelleration, but only 50% (or there abouts) of the locking pressure on decelleration. 2 way locks fully on accelleration and decelleration. (this isnt 100% accurate, but you get the idea).

a mechanical diff makes a huge difference to how the car handles, I would rate it nearly as much difference as fitting decent coilovers (on my R33, with 63,000kms on it). It puts power down better (car is quicker, esp off the line), the predictability is perfectly consistant. The rear doesnt step anywhere near as wide as with the stock diff in a straight line. In corners, you can feel the rear coming around, not just jumping wide (as with the stock unit) when traction starts to brake. I find the car seems to sit flatter in corners too.

If the rear does get too wide (with 1.5 and esp 2 way) taking your foot off the accellerator will result in it coming back in a very controller manner, not snapping around in the opposite direction. This is of couse unless you have left it too long, beyond the point of no return.

To give you an idea of the improvement in traction, previously in a straight line, I couldnt even drive the car off the line without chirping, and first and second were useles - not traction, wild sideways and just dangerous on the street if I tried to give the car too much - Just recently, I lined up another member off this forum, him with RE540s, me with crappy revspecs, but I was actually pulling ahead of him slightly (he is running 12s), we were both spinning the rears, but I wasnt just sitting there making noise and swaying across the lanes.

2 way a disadvantage? depends on what you are after. much better for drift, and a little more predictable if you are coming off the power during oversteer (esp heavy oversteer) - but a little more understeer. Well, I can also add, that after fitting the 2 way, I fitted adjustable castor rods, where previously I had castor bushes (that gave me 7 1/2 deg castor). The rods are adjusted about 1 cm shorter from the bushes, and turn in is just amazing - the car handles like it is much smaller. (and besides, as $350 for a 2 way, there is no way I was going to pass it up:p)

A mechanical diff can be a bit clunky, and chirp the inner wheel when turning in a tight circle - another downside is the back end gets out alot quicker in the wet than with a viscous diff, but once again it is predictable, and if you drive suitably, not unstreetable at all (unlike an old GT falcon I owned, couldnt corner in the wet, esp if braking into traffic, bloody thing used to do 360s all the time)

Anybody who is thinking of doing this - do it NOW. Not only is it a great handling mod, you get the power down much better, and the car is alot quicker to drive, straight line and corners. I actually thought I had a 4.3:1 ratio (vice R33 4.1:1) at first, the difference is that much.

As mentioned there are different types of LSD, mechanical and viscous are but two.

[Steve]

Another thing to think about, if the stocker gets re-shimmed too tight, it will die - Joel and Enrico, I would recommend you take the car to a diff specialist. If eigher of you need to go for a spin in my car, to see how the 2 way feels, give me a hoy.

[Jay95R33]

Great post Steve - you summed it up perfectly

[fatz]

if your lsd is shagged a good mechniacl is the way to go

pete

[EnricoPalazzo]

ill take u up on that offer steve

[Duncan]

"2 way (according to sydneykid) has an advantage if trail braking into corners. I dont do this often, but if you do get a corner come up unexpectedly (it has happened to me) and you are hard on the brakes into the corner, the weight can lift off the inside rear tyre resulting in sudden hard oversteer (the rear wheels are not working together, power goes to the wheel with the least resistance) - which can be pretty hard to catch. So there is a benefit in that it keeps power to both wheels."

Yeah, I should clarify that I'm talking purely for track handling, where corners shouldn't come up unexpectedly . As for trail braking, I regularly use that into long corners, even better when you left foot brake as well.

Of course, the main reason to trail brake is to stop understeer (dont allow the weight to shift back to the rear, keep it on the front, maximise traction), so yes, it does cause the rear to go light....and if you have calculated wrong you end up spinning in the corner (been there done that). And...thats exactly why I can't see the benefit of a 2 way diff, assuming it encourages understeer thats - why you were trail braking in the first place. Hope that made sense.

I'm happy to accept that 2 way may help for dorifto, I don't know anything about it....but I can't see a benefit for a circuit car?

Great thread here, anyone else using a mech diff?

[Cubes]

Steve,

HOY!.

[Steve]

Enrico, Joel, go pm. Weekends are best for me.

[Kinks]

Only just noticed this thread... my input is that mini-spools drift hard

(the last drift day - pfft. i've been practicing for the next one! mmm skidpan)

[FATGTS-R]

So whats the difference between a LSD and a locker? Not locker as in a spool or welded being locked 100% of the time but as in a detroit style locker? The previous owner said it had a detroit style locker diff. Its not locked full time as doing a full lock u turn there is no wheel skip at all. How do I tell if its a locker style or just a normal mech LSD? One thing that does happen is sometimes on take off, whether driving normal or trying to launch is that the rear wheels will " chatter ". Like when a wheel skips but its both of them and I am trying to drive straight. Someone told me its the diff locking/unlocking repeatably. I am not so sure though. As I have 265 rubber and I reckon its just struggling to spin up. Anybody know the workings of a detroit locker?

[B-Man]

Steve, where can I get a 2 way mechanical diff for $350 ??

[EnricoPalazzo]

by being lucky and the seller not knowing its real worth. try some wreakers or dismantlers.

[mist]

good answer Enrico lol...

[aKTiVE]

In my series of cars, its something i make sure of, when the clutch is dumped, both wheels are spinning.... nothing sh1ts me more than a vn v6 or something like that, with one stocky on the right rear doing a donut with the circumference the same as a trucks turning circle.

i had borg warner LSDs in my first 2 cars, they were great but over time with harsh treatment they started single wheeling more and more often... then i got a minispool, a lot of people were against that saying they were unpredictable etc etc... I thought it was great, it wasnt overly harsh when cornering at low speeds (city driving) and currently i have a Cusco locker.

The locker is VERY harsh and its so weird how something that sounds so harsh and bad is so good. I find having the locker the car is much more predictable when the rear wheels are losing traction, mechanical 2 way diffs seem a LOT similar to me, but the locker is definitely more harsh when cornering at low speed.

The bad thing is, it is a DEFINITE tyre f**ker. So if you have large wheels on the back, tires with even normal driving dont last long = Remoulds are a great thing =)

[Steve]

B-man, I got mine from Powerplay imports in sydney. The guy thought it was a 1 way, and was quite keen to unload it. First thing he said was 'I dont want much for it'.

I got lucky, he offered it for $350 fitted, I asked him if he could send it here for that price - he seemed glad to be rid of it.

When I unpacked it, and checked it against a couple of parts catalogues - found it was a Nismo 2 Way.

I agree with Dean, check wreckers and car dealers. Most dealers wont put a car on the lot with a 2 way diff - frightens the punters off:)

[lwells]

Is it worthwhile upgrading the stockers on a R32 GT-R? Say a 1-way at the front, and a 1.5 at the rear, inline with SK's comments?

LW.

[Steve]

yes, or a 2 way rear and 1.5 front

[B-Man]

Been speaking to a few fellas bout this

The Dorifto folks swear by the 2 way

For Track - 1 or 1.5 prolly 1.5

So I think I'll go for a 1.5. If anyone sees one going let me know as I'm on the hunt now.

I priced the 1.5 way Cusco locker and it was like $1500 from Greenline and that's not delivered. Ouch !

[Morgs]

Is it worthwhile upgrading the stockers on a R32 GT-R? Say a 1-way at the front, and a 1.5 at the rear, inline with SK's comments?

LW.

I wouldn't think its worth it unless you're planning big modifications?

Cheers,

Rick