3UZFTE

I would agree, no differential ever "busted" because of old/dirty fluid. However, the bearings are another story. I can show you a few owners on here that have had differential reasons for one reason or another. Your going to lay two treads if your in a situation with traction being equal, if your off-roading, racing, driving in snow, corner, the traction will differ, which will cause the spider gears to walk around, which is limited the amount of power being transfered to the other wheel. I feel like I'm beating a dead horse as you've even mentioned you understand how the open diff works, but the theory being that the spider gears have become harder to turn, causing a limited slip action... I just am not a believer in that, like he said, a poorly maintained diff will turn into a semi-LSD.

Can you do me a favor.... and take a picture of you doing a donut, instead of doing a burnout in a straight line, create a scenario where traction is unequal, which would be a controlled test. You mention you build theories on your experiences, which is no different from the rest of us, but with your theory is that you don't have a control as all of your LSD test seem to be in a straight line, again providing equal traction to both wheels.

mk2tmr2

iTrader: (1)

Just to clarify something. When i say a "busted pumpkin" I don't mean to imply that it exploded or the gears shattered. I mean that its function degraded to the point where it needs repair. For example, it's so worn that it howls as you're driving down the road. That's an example of what I meant.

With regards to the diff being a no-maintainence item: Did Lexus put a drain and fill plug on it? If so then I beg to differ. Perhaps my kid's grandparents would never need to change the oil in the diff on their LS - but they also have never done burnouts or drag-type launches. For the tiny percentage of us Lexus owners who drive very aggressively, most of the maintainence suggestions in the owner's manual don't apply.

JBrady

Quite honestly I rarely do burnouts. When I first got this car in 2003 I took it drag racing roughly 10 times. The best 60ft I was able to get was 2.18 seconds. The problem was the right rear tire would loose traction and spin hard ruining my run. With the drive by wire throttle and programming, with VSC turned off, loss of traction meant uncontrolled tire spin requiring complete throttle off. It definitely did not have the same traction the car has now. I can now spin both tires some while driving through the run something I could not do before. I have not been back to the track in years as higher mileage means higher probability of breakage. I did the test photo shown out of personal curiousity based on others pictures and reports. BTW, I had been drag racing for many years prior to the above and my times on my car should indicate I have a clue about driving.

The second picture posted was a twin turbo LS400 with the stock diff. It curves one way and then another. That would certainly change the tire load side to side. As I said I am not claiming this creates the equivilant of a clutch type lsd or a torsen unit. Interestingly I had an 87 Ford TBird Turbocoupe that I did a 5.0 HO engine swap. It had a factory 8.8" 3.55 LSD clutch type that like the Mustang would become an open diff as the clutch packs wore out. I personally rebuilt mine to regain function and was able to get 1.9 second 60fts on 245/55-16 normal radials. Car was a manual 5 speed and ran 13.7 @ 104mph.

I may try a "donut" out of curiosity but have fresh Michelins and it is against my nature to beat on new tires. Maybe. If I do I will post. I am not expecting dual marks but if that does for some reason happen it is most likely due to once the tires are spinning the friction drops and they may continue to spin even in a circle.

The nature of a clutch type LSD distributes torque equally. This can allow loss of traction of both tires in a turn which can catch an inexperienced driver by surprise and cause loss of control. The torsen is better as it meters torque between the tires and is less likely to spin both tires. Arguably an open diff is least likely to cause loss of control as the inside tire will spin but not the outside so there is less traction loss. Of course all the above assumes enough torque is applied for the conditions to create spin.

JBrady

The manual has diff oil changes, as well as trans fluid and filters, listed for "Special Operating Conditions" which are:
Towing a trailer
Repeated short trips in freezing conditions
Extensive idling such as delivery or patrol car use
Use on rough, muddy, unpaved, dusty or salt covered roads

Not that I am against changing diff oil as I did change mine. In fact this may NOT stop the condition I am reporting from happening.

A howling diff is generally due to the ring and pinion gear not meshing properly. This is usually the result of improper set up during installation. Bearings can wear out and begin howling. It doesn't appear that this is a common issue on these vehicles but the increased traction does appear to be the norm.

Most of the RWD over the last 50 years have a solid rear axle design. When the engine applies torque the axle "tries" to rotate and this applies downforce to the driver side tire and lifts up on the passenger side. On independent rear suspension RWD cars this effect is reduced BUT the rotation of the car from torque is still present and explains why my car use to spin just one tire at the drag strip and on the road on flat dry surfaces. My car now spins both tires on dry flat surfaces in a straight line. Many others report and post pictures of the same. Draw your own conclusions.

For those that choose to believe that this is normal and not due to age and wear... that is fine. I have made the case with solid evidence. I stand behind my points.

98Gs4001UZ

I spun both tires in my 98 gs400 with 71k miles on with the stock diff. Then I switch the stock diff with the diff out of a gs300 with about the same miles and got the same effect the other day.

3UZFTE

The operation of an LSD is to limited slip of one wheel, and transfer it to the other, it doesn't meter any power. As one wheel starts to slip, it causes the spider gears to walk around the diff, an LSD starts to spins, and depending how it's built, torsen/clutch type, it basically shifts the power from the free spinning wheel to the slower moving wheel, thus limiting the slip of the differential. Just because the vehicle is doing a burnout and manages to wiggle sideways, it doesn't mean that it's changing the amount of the friction between the two, more than likely the power from the drivetrain makes more power to overcome the friction that other wheel can stop.

I'm not arguing that you can't spin both wheels, if traction is equal, your going to spin both wheels. If your stuck on ice, in mud, or off-roading, I can promise you that you'll find out what an open diff drives like. On dry pavement, it has very little use. Going from the GS4 to the GS3 is going to increase your low end torque, but decrease your overall speed and horsepower. the 3.26 isn't bad, but the 3.92 will definitely spin the tires a lot easier than the GS4 diff, but you've got 300hp, you should be able to spin the tires.

I think at this point, we can agree to disagree, an open diff will leave two tire tracks EVERY TIME that the friction is equal between both rear tires. If your creating a scenario where the friction is different, I can promise you, you will spin one tire, hence why my Lexus RWD cars don't leave the driveway in the winter. FYI the only Lexus that left the factory with an LSD is the IS, which uses the older G-series diff.

JBrady

Actually, that is not what a limited slip is refering to or doing. A limited slip is a differential that uses clutches (friction plates) to STOP the differential action. When differential wheel speed is REQUIRED for cornering these cutch plates SLIP and allow the differential action. This is the SLIP in LIMITED slip. It does not refer to tire slip.

Actually we AGREE. If each tire has equal traction an open differential will spin both tires. The point I make is that is USUALLY not the case with a high torque RWD car. I expained why this is the case in previous posts above.

What you HAVEN'T explained is what I HAVE explained... why these cars when new spin one tire on a full torque launch but when older spin both under the SAME conditions. This is a documented situation. My theory is a solid explanation for why.

98Gs4001UZ

Even though I can spin both tire in a straight line. Yesterday I noticed that when I pulled out of a driveway onto a wet road. *I gave it alot more gas than I should of trying to get side ways and it felt as if the wheel on the pass side was just spinning, my drivers side wheel had no power at all. Preventing my from getting as sideways as I'm used to in my corvette which has a limited slip diff.

JBrady

As designed the clutch pack in an LSD resists the differential action (one tire spinning) while slipping and allowing it for turns. This increases traction by keeping torque applied to both tires even if one loses traction. However by design the clutch pack can only hold so much torque and if conditions are right it can be overpowered by engine torque and one tire can spin.

This is actually somewhat common on solid axle cars with enough traction when the LSD clutch pack becomes worn and less effective. This happened on my old 5.0 Ford LSD (happens on most Ford 8.8 trak lock axles) and would spin just one tire. Kind of the reverse of what seems to be happening here. In that case wear reduced internal frinction of the clutch packs where our cars seem to gain internal friction with wear.

In your example by putting one tire on a slippery surface the internal friction was not sufficient to prevent the differential effect. As you noted an open differential can actually be safer for an average driver in slipperly conditions.

jrowedem

i find this thread quite hilarious. and Obviously Misleading, Jbrady what does driving experiences have to do with anythings about the operational differences between a LSD and and OD...

Also, if you agree with 3UZ then i would retract your first statement if i were you... but i'm the type of person who admits when i'm wrong.

JBrady

I find it "hilarious" when a person with 7 posts on a forum decides to insult someone who has been a long time contributor to the forum.

It is unfortunate that people feel free to be rude online when they probably... even hopefully... would not be rude in person.

Respectful disagreement is reasonable and acceptable. Direct and or implied insults are rude and unacceptable. Maybe you are the type of person that apologizes after realizing they have insulted someone... we shall see.

jrowedem

Well I'll apologize for being as coming of as rude. I have had to develop a brusque attitude. So my words may have to be taken with a few grains of salt.

I simply don't believe in ignorance, or tolerating it. especially for someone claiming experience, and seniority to say some this wrong this and spread to a distortion which could lead to someone less experienced damaging their vehicle. that to me is unacceptable, even the moderators couldn't educate you on your misconception. but to each is own

this isn't a disagreement, just an understanding.. I understand what your thinking, i also, can understand your perception. but that doesn't mean your right. but thank you for being so observant and eloquent and this makes post #11

JBrady

Well, you start with an "apology" for coming off as rude. So I can assume your next paragraph is an intentional insult. You may or may not do that face to face. I would rather hope you would not.

Your second paragraph is condescending but finishes with a "thank you".
I do not know you and you have limited posts for one to draw a more balanced perspective on your motives. From your limited effort I can only guess that by taking a self rightous attitude and calling me out without explaining your differences you are not interested in the discussion but rather in self aggrandizement.

So, even though it may fall on deaf ears... care to explain how my statements may lead to "someone less experienced damaging their vehicle" ???

mitsuguy

iTrader: (2)

This is the first time I've read this thread, and, I gotta be honest, lack of changing differential fluid can and will lead to differential failures. Diffs in the Toyota/Lexus group hold up pretty well regardless of maintenance, it seems, but, by not changing the fluid, you allow dirty fluid to keep circulating. Fluid, over time, wears out, period. It breaks down and becomes thinner and the actual protection is degraded over time. The dirt (in this case, small metal particles) that circulates around, does nothing but wear out the ring and pinion gears that much faster. If you had seen what I've seen come out of rear differentials, you might be singing a different song here.

I don't know what your background is, but it doesn't seem like you have much background in vehicle mechanics. Have you ever taken a differential apart? It is physically impossible for what you propose is happening, to happen. Inside a differential, you have a ring gear, pinion gear and the spider gear assembly. There really isn't anywhere for friction to "increase." Aside from the gear mesh, there are no parts that slide over one another, so adding friction inside the unit does nothing to increase the likeliness of it acting more like a LSD...

As have other posters in this thread noticed, I have too, that cars without LSD's, on hard flat dry clean ground, spin both tires and leave an equal burnout... I have also taken the same car that was capable of that, gone and done the same thing, but doing a donut (this was a 180k mile SC400), and found when I was done, a single burnout track...

Lets examine why cars with open differentials spin one tire more than the other... pretty simple -
neither axle is directly linked to the driveshaft but they are both connected to the spider assembly in the carrier. The carrier is driven by the driveshaft through the pinion/ring gear. When the spider assembly rotates forward, the axles can both rotate forward, or, one can stay stationary or even spin slower, making the other axle spin faster. In ideal situations, both tires provide traction to accelerate the vehicle. In situations where one wheel has less traction than the other, the one with traction may not spin at all and the other without traction (its easier to spin just one wheel/tire vs pushing the entire car forwards) will just spin and spin (actually twice as fast as the speedometer indicates if one wheel is not spinning). The only way in a standard open differential to get both axles to spin the same way all the time would be to prevent the planet gear from moving (http://en.wikipedia.org/wiki/Differe...hanical_device)). Dirty/worn fluid will simply not do this. If, perhaps, that planet gear was wearing, causing it to not spin freely, that is one thing, but it has nothing to do with the fluid, and, if the planet gear is wearing, the other gears are as well, which is a bad thing.

Let me propose one other possible reason that the "peg legging" is more apparent when a Lexus is new as opposed to old... Stiff suspension. When a car is new, all of the suspension bushings, shocks, etc are nice and tight. The springs are as stiff as they will ever be. As a car ages, the rubber bushings become more pliable and move easier. The springs don't have quite as much "spring" in them anymore and shocks tend to wear internally (and the fluid thins), essentially making it seem like you have a softer shock/spring combo as the vehicle ages. More like solid axle cars that may have a higher tendency to peg leg in a burnout, a newer Lexus may have more weight transfer when doing a burnout than an older Lexus simply due to the tightness of everything when new...

Last but not least - this phenomenon that you speak of - may help drag strip performance some uber small amount, but, come drive down my street with a RWD, open diff car (I don't care how many miles it has and how much it acts like it has an LSD) when it snows, and we'll see who is making it around just fine in their factory equipped LSD car (IS300, w/ LSD), and who can't even get into my driveway...

edit: Just to clarify about that whole planet gear and wear thing... it is likely, if the planet gear is actually messed up bad enough that it doesn't spin, that will also be apparent when making tight turns and you should hear and feel the rear end of the car and tires making all sorts of noise and even shuddering as you turn...

BayAreaLex

Interesting read and debate. Been tinkering with cars for about 14yrs and have done plenty rearend work and have never heard of anything that the original thread starter points out.

Can anyone recommend a rebuildable LSD from another car that is compatible with the GS400/430 Gen2?