JBrady

Ok gang, no LS4xx came from the factory with a mechanical limited slip differential. Some (all?) LS430s come with an "electronic" LSD which uses the ABS system to create the effect.

ALL conventional differentials power both wheels EXCEPT when one tire looses traction and then ALL the torque transfers to that tire creating the one tire burnout or "stuck in mud" effect.

Clutch type LSDs use clutches to create friction between the spyder gears and the case which keeps both tires powered (usually) even if one tire looses traction. Cars with factory LSDs (and other types of differentials such as Torsen and lockers) will create two tire burnouts. The burnout is less important than the effect and that is MORE traction allowing MORE power/torque to be used before loosing traction. Important for many situations and actually potentially dangerous in some situations.

The stock LS400 differential (and many other Lexus Toyota vehicles) has a VERY interesting reaction when the miles climb above 80k-100k or so. The friction in the spyder gear to case area increases. This results in a FREE LSD!!! No money, no work

My 99 LS400 is past a buck fifty so I decided to check to see if my "LSD" had been "delivered"???

You bet.

Och

iTrader: (3)

Uh, no, thats not an LSD effect. An open differential will always send the same amount of torque to both wheels, and if both wheels have equal traction and theres enough torque to send them both spinning, they will both spin. Now put one of the wheels on patch of ice, and keep the other wheel on pavement and see what happens.

As far as "electronic LSD" effect, it is horrible on GS430. I don't know if it is any better on LS430. The VSC system along with throttle by wire completely shut off throttle during the suposed "LSD effect" so its absolutely useless. The simple "TRAC" system on 1st gen LS400 works much better, it alternates brakes and only partially shuts down throttle, and it will slowly but steadily get you unstuck from snow.

PureDrifter

iTrader: (10)

electronic and "friction worn" LSD effects are nothing more than cheap imitations. for true LSD the only way to go is clutch type, or Torsen/fluid coupling if you want something more suitable for every day. try doing a donut in your car, you'll be roasting the inside tire.

TJW98LS

iTrader: (1)

I roasted both tires doing a donut in my old LS400.

PureDrifter

iTrader: (10)

before or after you did the suspension on it? (did you ever?)

JBrady

Uh, yes, this is in fact limited slip. Regarding how a differential works please refer to my third sentence/second "paragraph" and you see that your statement is in agreement with mine.

Limited slip refers to the limited clutch slippage in a clutch type LSD. The internal friction created as miles acculate creates friction like a minimal clutch. As you and I state differentials power BOTH wheels/tires but as I state send all power to one tire if traction is compromised (stating this in agreement I am sure with yourself but for clarification for the board). The result is actual traction to both tires under spinning conditions UNLIKE the stock which will BLAZE one tire if traction is lost. Trust me, I have done this a BUNCH both on the street and at the track. Previously under hard accel and with the stability control turned off if one tire lost traction it would rev HARD and with the poor response of the throttle by wire it was not controlable other than letting off the throttle completly ruining the run. On most cars I can drive through the spin but not with my car at the track back under 50k miles. I just ran a couple quick 0-60s with my GTech Competition for comparison since I am doing headers and exhaust soon and was able to drive through the spin just fine and ran 6 flat.

I loose track a bit in my posting and cover this subject in the GS section where I state that this is in a STRAIGHT line only as the friction is not enough to work in turns and therefore does not give the benefit of a true clutch type LSD or a torque sensing type TORSEN or a viscosity type or any other engineered type.

I agree that the Lexus traction/stability control SUCKS and kills the engine power instead of providing enhancement AND power when needed such as pulling out into traffic only to loose traction loose power and start cussing.

Och

iTrader: (3)

Yes, but if both tires lose traction at the same time, they will both spin. From that pic it looks like you went in straight line, both wheels were on the same, fairly smooth pavement, so thats exactly what happened. Just think about how open differential works, thats exactly what's suposed to happen.

However if one tire lost traction first, it would spin without letting the other tire catch on. Try it with one wheel on a patch of ice or pour some oil under one of the wheels and see what happens.


It only sucks on the newer models equipped with VSC and throttle by wire. The old TRAC system with throttle cable works pretty well.

JBrady

Well, in a laboratory under strict testing and load balancing... that could happen. In real world driving it virtually never happens.

In my 35 years of driving I have driven mostly torquey rear drive V8 cars. ALL of them that had open differentials would spin only ONE tire... until now.

The reason is torque multiplication of the gears creating a difference in side to side traction. Torque multiplication in 1st gear (on 5 speed Lexus V8 models) is 3.357 and the diff is 3.266 giving total multiplication of 10.964.

This means that the engines torque, say roughly 250 lb/ft at 2500rpm or so (on my 300tq @ 4000rpm engine) places 840 pounds of force to rotate the cars differential and 2740 pounds of torque the tires must control.

The rotational force lifts the right side of the car while forcing the left side down. This substantially reduces the traction on the right side tire while increasing the left. This is why the right side will spin on a open differential car. (rear drive, clockwise engine rotation).

Why this is important for this discussion is when trying to accelerate from a stop in the quickest possible manner you do NOT want to loose traction at one tire on an open differential.

BUT, as I described, your Lexus / Toyota diff has enough wear and tear and has internal friction it will be ENOUGH to hold traction for BOTH tires. This is GREAT news for off the line traction.



Thats good to know but doesn't help those of us with 1998 and newer models. For us wanting performance the Lexus systems are terrible.

ghettolex1

just yesterday it rained and i floored it burning out both my tires.
i have a 91 ls400 bone stock with a brand new engine with about 25,00 miles on it

3UZFTE

Its because both wheels lost traction at the same time, and both tires had the same amount of traction.... Try doing a doughnut while holding the pedal to the floor, you will smoke the crap out of the inside tire....Or wait until snow flies, you will really be able to tell the different between LSD and non. Just the way that our open diff is made, it is impossible to get a "LSD" from out setup, as there is nothing to stop the spider gears from walking, as there would be in an LSD. I have an 01 GS430 with the VSC, still uses the open diff, but I can chirp both tires, but when traction is unequal, only one tire will spin.
Open or standard diff.

LSD


I just don't see how even wear... can cause the spider gears in the open differential to act like the LSD... Even if the gears kind of bind up, that is how the diff works, the spider gears will just walk and transfer the power to the other side... Also, if the spider gears were to wear and cause a little binding to spin both axles, you would notice this when your turning as one wheel will be skipping across the pavement, like the Detroit lockers. Basically your saying that by the years of wear, your gears are acting like if you had welded the spider gears, an old hotroding trick. Just trying to figure this out, cause an LSD works by allowing slipping around corners, obviously, and as one wheel starts to spin, the power is then sent to the other wheel to reduce one wheel from spinning.
The easiest way to identify an LSD is to jack up the rear end so the tires are off the ground, spin one tire forward, the opposite side tire will spin the opposite way if it is an open diff, if it is a LSD diff, the tire will travel the same direction your are turning it.

Kingsoup

Dry pavement is one thing, but I've been through 2 serious winters now, the Ls400 Celsior has an open Diff, if you get a semi lsd effect, it sure as hell doesn't happen on slippery surfaces like snow and Ice.

The only comfirmed LSD swap I've seen so far that fits is the Torsen LSD from the Mk4 Supra, but they are real pricey, I really need an LSD to improve winter traction in this car.

Schnitz

iTrader: (5)

No, you need winter tires and letting off the right pedal will get you all the traction you need.
I've driven 450whp cars in the winter with no problems. It's always the nut behind the wheel that needs repair.

SRV1

iTrader: (2)

When I got my car earlier this year, I did a burnout and both tires laid rubber. The car only had 97k on it. I own a Mustang and had various other cars and trucks with some kind of traction device in the rear and all the open diffs NEVER burned both tires on dry pavement. Now this question may have been asked before but has anyone ever physically taken apart a LS400 rear diff? Also in snow both my wheels spin so something is going on in the rear of our cars that is not supposed to.

James

3UZFTE

Yes, we have. The reason why your laying rubber on both tires is because the traction between the two wheels are equal. Even in snow, same thing, both wheels are being equally powered. Now, someone very well could have installed an LSD inert in your LS4 housing. Try doing donuts on dry pavement, you will find that only one wheel should spin because the traction between the inner and outer wheel are different when cornering, but not so much when your in a straight line. If you look above in some of my previous posts, you will see the innards of the LSD vs. open diffs.

I see that you have an SAS'd Pickup, a nice Runner, and a 2UZ swap... got some pics? I think part of the Mustang getting traction is those Foxbody's are a hell of a lot lighter than out LS4's, especially in the read end department.

sdls

My blown LS4 will lay two fat rubber marks for as far as I want them to go :