I posted in the LS section how my (and many other) Lexus LS, GS and SCs seem to have Limited Slip Differentials (LSD's) even though none of these cars had one installed from the factory.

In answering the responses and reviewing our Open Differentials (OD's) in the factory repair manuals I can make the controversial although ACCURATE statement that over time the 1990-2004 stock OD's will slowly become actual LSD's. This is due to the internal parts slowly wearing into each other and creating more and more internal friction.

Further, in reading the manual it appears that it is likely that we could actually build the stock unit to be an LSD using stock parts. This seems hard to believe but the evidence is overwhelming.

When new the mentioned cars would spin ONLY one tire when doing a burnout. This is normal OD operation. An OD provides equal torque to both tires UNTIL one tire looses traction and then transfers up to 100% of the engine torque to the tire without traction. This is why one tire smokes.

LSD's are designed just like OD's except they have friction increasing parts that restrict the torque from overpowering one tire. This keeps equal torque going to each tire and is why LSD equipped cars smoke both tires when doing a burnout.

The LSD's friction increasing parts are designed to SLIP when cornering because the outside tire needs to rotate faster than the inside tire. So this SLIP allows the differential to do its work and allow a differential tire speed. This is the reason for the name Limited Slip.

Torsen differentials such as installed on Supra Turbos are not limited slip. They keep torque applied to both tires by an ingenius gearing system. They will also spin both tires in a burnout and will allow differential action but there is no slipping of friction materials so they are not limited slip even though they are commonly called LSD's.

My dragstrip times in my sig were done around 50k miles. At that time my car would easily smoke just the passenger side tire.

Also, the OD in my car is identical to the GS400 and GS430 through 2004. It would be interesting to have members test their cars traction and report back if they smoke one or both tires and how many miles they have on their car.

Here is my STOCK OD 1999 LS400 showing my LSD function due to increased internal friction with 170k miles. I am guessing somewhere around 100k this will become the norm for the cars mentioned. It is probably helpful NOT to change the diff fluid as specified.

 

Interesting information... I can say that, this is not the case for me around turns. In a straight line I'll have to report back.

 

I left the same tire streaks with mine. Lil brake torque, 285's in the back, it was pretty. But in no way do I think I have an LSD-equivalent with 110k on the clock. It was just a lucky launch.

My driveway is curvy, and on a hill. Occasionally, if one tire goes off the pavement and into the grass, I'm stuck. It directs 100% of the power to the wheel free-spinning in the grass. Freakin' worthless

I think leaving tracks like that is just more of an "even loss of traction" instead of peg-legging. Kinda luck of the draw or something, when you have just the right launch

 

I take it WET grass? Yes, it requires a reasonable amount of traction to both tires and going around corners has the OD moving internally so that is not likely to work in turns.

I am certainly NOT claiming this makes for an equivilant of a factory engineered LSD or Torsen. I AM saying that this improves traction, in a straight line, from a standing start in drag racing type efforts.

 

I'd like to say you didn't, but you did in this case say that it does, nor do I recall you mentioning a "drag type effort". What I can tell you though is that I have seen what you describe on many vehicles in a straight line application.

 

Not sure what you'd like to say I didn't (say)?

The more I think about this curious effect another possibility comes to mind.
Instead of the parts "wearing together" and creating more friction it is also possible that as the thrust washers wear more clearance is created.
When torque is applied from the differential housing through the spider gear shaft the bevel on the spider/side gear interface forces these gears apart more and that creates the increased friction. That and or combination of both conditions.

 

100,000 mi. peg leg gs 400..... always.

 

Interesting. Tested recently on a flat dry even surface?

 

No offense, but the entire premise of this thread is a bit silly.

No...neglecting to perform routine maintenance on your factory equipped open differential will not magically transform it into, and I quote, an "actual LSD" over time. It will, however, cause you to eventually replace your broken factory differential. If you choose to replace it with an "actual" LSD, then I guess in some weird way the OP was right.

I wager that if that same burnout picture in the original post was done with about 1/2 turn in either direction on the steering wheel we would have seen a very different stripe on the pavement. (Note....not "stripes")

I've owned a few high-performance RWD cars with open differentials and I could get all of them to lay nice 11's on the pavement if I wanted to. Where a LSD **really** comes into its own is when you're powering out of a corner. That's when you really notice how crappy an open diff can be.

 

surface had no effect.
and yep, coming out of a corner hard with an open diff. the car just smolders the light tire. propelling me nowhere fast, and if you pedal it to control spin, your still a snail.

 

Specifically WHICH H/P RWD cars with open diffs have you been able to burn both tires with? I have been driving and building powerful RWD cars for 35 years and find this to be the exception. Please add whatever you can of value to the discussion. If you review almost any of my nearly 3000 postings you will find mostly factual and technical data so I practice what I preach.

If you have read my posts here you will notice that I REPORT that my car originally spun just one tire in a straight line on flat dry surfaces. In my quest for improved launches "drag race type" I purchased what was supposed to be a TORSEN diff from a Supra Turbo. It was not. So I did not install it. Over time my car went from spinning one tire on launch to spinning both with MUCH better traction off the line. This to me is valuable and probably is to other readers.

Nowhere am I claiming that this constitutes a full function limited slip or torsen. Nowhere did I claim that this works in cornering.

What is your statement based on?
"No...neglecting to perform routine maintenance on your factory equipped open differential will not magically transform it into, and I quote, an "actual LSD" over time. It will, however, cause you to eventually replace your broken factory differential."

Can you offer another explanation on WHY my car when from spinning one tire to spinning BOTH? Can you back up your claim that not doing routine maintenance will result in breaking the differential (in some drastically accelerated way)?

If you want to challenge any of my statements... fine. You are free to do so. I would only ask that you take the time to explain, as I have, why you disagree.

 

Thanks for your civil and thoughtful reply. I welcome this open discourse.

My main contention with your original post is based on 2 statements that you made and how they will likely be interpreted by the majority of readers.

1) The thread title is "Differential Facts". This implies that the contents of the thread are based on scientifically proven data and will hold true for all owners of cars that meet the same criteria as yours. However, the contents of your post are all conjecture based on assumptions and very limited observations of a single car with a single driver.

2) You make a bold statement, "I can make the controversial although ACCURATE statement that over time the 1990-2004 stock OD's will slowly become actual LSD's." (Did you add "controversial" later? I may have missed it the first time but I don't remember it being there.) The idea that a poorly maintained open differential will become an "actual LSD" over time is a stretch of the imagination that defies practical logic and common sense. To add fuel to the fire, it's framed up in the context, while not explicitly stated, that this is somehow a rational way to upgrade your car's performance. I would contend otherwise.

To list a few:
Toyota MR2 Turbo (x2)
Toyota MR-S
Mercedes C32 ///AMG
Mazda Miata
Chevrolet Camaro (3rd gen)
Lexus GS300

The list above represents a vast diversity in drivetrain configuration, horsepower, suspension designs and tire compounds. Some brake torqued, some clutch dumped, all left dual skid marks on demand.

I have no doubt that what you experienced is true for you. I have no intentions of making you out to be a liar. So please forgive me if that's how I was interpreted. I have a feeling some other factors, other than differential wear, may have contributed. Something as simple as tire pressure could make the difference between a one-tire-fire and a full burn out.

Actually - that's exactly what you did and one of my main points of contention.

My statement is based on common sense. I can safely assume someone needs a LSD in the first place is driving their car hard. I've tracked enough cars to know that hard-driven cars need to be maintained at a level above and beyond a normal street-driven car. If you need a LSD (drive your car hard) and instead decide to just never change the fluid in your rear diff because someone on the innernetz said that it will give you LSD, you're likely to find yourself with a busted pumpkin.

• tire pressure
• tire compound/wear
• tire/air/surface temperature
• you got braver with the gas pedal than previously (driving variance)

Do I really need to explain why allowing the oil to degrade to the point where your differential is ceasing to function normally is a bad idea?

I admit that your premise has some theoretical value to it. However, I wouldn't label it as a "differential fact" and I wouldn't recommend anyone consider this a viable performance enhancement.

 

I'm with mk2tmr2 on this one. But I definitely appreciate the knowledge yall bring to the table, on both sides. This is the healthiest discourse I've seen on any interwebz forum in a while, lol. WHEN DO WE GET TO PUFF OUT OUR CHESTS AND TALK SMACK THOUGH?!?!?!

 

Again.... Sigh.
I feel like we have this discussion weekly. Facts and theory don't always go in the same sentence. An open diff will never turn into a LSD, it just isn't built into operation of the part. Trust me, after a few years driving in my GS over the winters, mine doesn't operate remotely close to an LSD. Although I think I am going to weld up my GS300 3.92 diff and try that this summer.

On a slightly different note, has anybody looked into an Aussie Locker, also known as a lunch box locker, for our diff housings?

 

Your reply reminds me of how I usually reply with effort and thought. This is always welcome. Let me address each of your points as to move this forward. This by nature is labor intensive and creates a long post but is needed to address each point.

Thank you. Your respect is welcomed and I will endeavor to respond in kind.

The scientific method is one of observation, theorizing and testing of the theories with adjustment as necessary. My observation is not limited to my own car, far from it. Search by my name and LSD and 90 responses are returned dating back 10 years and my experience goes much further back than this. However as recently as 2003, based on my relatively long history of testing and observation, I did not believe that an open diff gave the consistent ability to spin both tires.
Both in threads, PM conversations, purchases and actual time at the drag strip my theories and testing involve roughly 20 Lexus LS, GS and SC vehicles that had open diffs.
A couple Lexus examples:
https://www.clublexus.com/forums/sto...ut-pics-3.html
https://www.clublexus.com/forums/sto...nout-pics.html




No, check the post, no editing has been done. Yes, the statement is bold and meant to start the conversation.

I guess we differ on what constitutes “poorly maintained”. My factory LS400 owners manual has NO differential oil change interval unless driven in “special operating conditions”. Even so I changed mine at apx 70k miles. Most of us “old” guys grew up NEVER changing fluid unless to repair a leak.
The FACT is that the way an LSD is designed uses clutches to increase the resistance of the spider gears rotating. This makes it much more difficult for one tire to lose traction (but not impossible). When new most Lexus open diffs will spin one tire. Most that have tried it find older Lexus vehicles spinning both tires. Observation indicates a change. I have described a valid theory that testing has not disproven. Increased internal resistance is increasing traction in the SAME manner that an engineered LSD increases friction and traction. It functions the same just not as robustly as if internal clutches were present.

Interesting list and I must say I am surprised. I have a lifetime of driving V8 RWD vehicles and the Lexus examples I first noticed in 2002 were the first examples of open diff cars spinning both tires. I was truly in disbelief and not until I observed multiple examples did I begin to formulate my above theory to explain it. Do you have any pictures of your cars doing so? Possibly the independent suspensions reduce engine torque unloading one tire. In the MR2 it is transverse so that would eliminate that variable. I assume the Camaro you list is not a Z28 which usually had factory LSD.

As noted I was a disbeliever until forced to drop one theory and develop the current.

Where did I do so? I specifically stated otherwise. Re-read my post #4 above. Also unedited.
I challenge you to show me a differential that “busted” because of old fluid. Not some other reason. Specifically old fluid. Differential fluid changes are more for dealer profits than failure prevention.

I used my vehicle because I can make specific statements without relying on anothers reports. That said this condition has been reported to me with multiple vehicles, drivers, conditions with the common denominator of higher mileage.
Your list is viable but is not the case for my car and the evidence as I see it supports my theory.

As stated above differential fluid changes are normally not required to maintain safe operation.

Thank you for that consideration. The fact is this appears to happen regardless and increases traction which is a viable performance enhancement. Actually, since I changed my fluid it may happen with or without service. IMO it is a GOOD thing that costs nothing and does not noticeably reduce reliability. Obviously "the harder you run the sooner you'll break" applies to ALL vehicles of any make and is "relative".