Oem torsen LSD test (Need volunteers)

Suspension and other discussion

Postby coyoteboy » Mon Apr 16, 2007 7:48 pm

I dont remember seeing it as a "dealer" option, but bear in mind that Toyota have been capable for many years of ordering a "custom spec" vehicle from the factory based on your order in the dealer - which is what happens today with many manufacturers.

Many toyota 4x4s came with option packs too, but all have their vin plate "axle" specification correct for the type of diff spec'd?
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Postby SowndWave » Thu May 03, 2007 4:10 am

I am currently doing my whole rear suspension, diff, and subframe bushings. So i'll take a peek in through the plug holes and test out the diff on the bench. I have a feeling its an open diff unfortunately...

Though I really wish it was torsen...
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Postby SowndWave » Sat May 05, 2007 8:49 am

Time for some enligtenment.

First, If you do not know and understand fully how an open aka conventional diff works. Go here and learn it: http://auto.howstuffworks.com/differential2.htm

I tend to go into too much detail, so if you have A.D.D. you might want to skip ahead to the summary at the bottom.

Torsen AND Open Diff's:
--Spin both rear wheels in opposite directions with the input shaft(pinion) stationary.
--If you try "test 2" and have the pinion spinning (jack up off the ground all four wheels and let idle in first gear), hold one wheel still, the other spins double speed of the pinion.
--If you resist the 2X spinning wheel, the stationary wheel you are holding will begin to have torque transfered to it and will start moving.


Now, the difference is indistinguishable. They both perform the EXACT same way in standard operating conditions. The difference lies in this; Open diff's supply torque to the wheel with the least traction, whereas Torsen diff's transfer torque over to the wheel with the most traction. However there is an exception, if on the Torsen set up a wheel has 0 traction, it is rendered useless and becomes a completely open diff unable to transer torque to the wheel with traction.

Test #2 tells you, you have a differential, it doesnt help with determining Torsen or Open. While doing the test, what WOULD indicate this however would be if you could actually measure the torque on each rear wheel at any given time and compare them side to side where you would see the torque split occur and which wheel it goes to.

Open diff's transfer the torque evenly, always. Straight line on perfect dry pavement each side of the rear wheels has 25% of the total engine torque, remember we are AWD and 25% to each wheel = 100% at the engine. If one wheel is on dry pavement, the other on wet the coefficient of friction is different. Now the wet wheel might spin a bit here and there, leaving the diff with 10% torque on the DRY wheel, and the remaining 40% on the wet wheel, because open diffs transmit power to the wheel with least traction.

Torsen diff's transer the torque depending on its gear ratio torque bias. Once again straight line with perfect traction both rear wheels have 25% traction. If we have the same scenario with one wheel dry, one wheel wet, and the wet one having a small ammount of wheel spin, the torque to each wheel changes. Torsen transfers the torque away from the wet, spinning wheel to the dry, grippy wheel depending on its torque bias. If it was a 5:1 torque bias, the dry wheel now gains 40% torque, and the wet spinning wheel gets 10% of the torque.


NOW, if thats explained properly (god I hope so and I hope you all gain something from that and I didnt totally waste my time) then I will summarize my results:

SUMMARY
--Test # 2 gives you no indication whatsoever of what diff you have.
--Pulling the drain plug on the bottom of the diff and shining a pen light up inside and being able to see the worm gear/wheel sets gives you an indisbutable result.
--Without being able to test the torque acting on each wheel, visual inspection is the best way to determine if you have a Torsen or not.


That said, I found out I do have a Torsen, and I'm quite happy with that. Questions? Comments? Concerns? Complaints?
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Postby mike325ci » Wed Jun 13, 2007 6:49 pm

Finally a resolution to this question! Thanks for the info. Visual inspection = only way to check, got it...!
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Postby BriinumsBo » Thu Mar 13, 2008 10:10 am

SowndWave, what is oyur transmission/diff code ?
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Postby Corey » Sun Dec 07, 2008 8:28 pm

According to this page:
http://www.geocities.jp/miz_rc/sisutemuzenn3.html Use google to translate, and it says Torsen LSD

All JDM ST185's of all years came with the Torsen standard.

I haven't tested my car yet. Also, my tranny code is E150/737....

So if Soundwave's is the same^^ and since he also has a jdm car, its likely mine has a torsen aswell, supporting the info on that site.

EDIT: more cool Torsen LSD info
http://www.geocities.jp/miz_rc/4wd.html
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Postby Gary ST165 » Mon Dec 08, 2008 12:20 am

fact: my friends jdm feb 1991 st185 narrow body does not have a rear LSD. It has been inspected with a boroscope.

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Postby Corey » Mon Dec 08, 2008 12:27 am

Now i just need to check mine - looks like the info on that site isn't entirely correct
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Postby smog7 » Mon Dec 22, 2008 7:26 am

since rear lsd has larger axle stubs, why doesnt someone with an lsd measure the stub width??
Last edited by smog7 on Mon Dec 22, 2008 6:54 pm, edited 1 time in total.
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Postby RedCelicaTRD » Mon Dec 22, 2008 8:11 am

If I remember right the stub portion that you can see will look the same. They are different where they enter the diff carrier itself, so you can't see it.
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Postby CMS-GT4 » Mon Dec 22, 2008 6:00 pm

You would have to pull the stubs as said below. There might be a slight difference right at the base of the housing on the shafts but I can not remember and I no longer have my old open dif.
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Postby timmey » Fri Feb 06, 2009 6:01 am

Dammit!

I have a E150F - 734 tranny in my 1991 GT-Four A. :shrug:

I noticed that no one else has listed 734, any idea what that one is? Plain-old LSD :(?

From what SoundWave is saying the test is inconclusive, and my diff was just filled with Royal Purple and I don't want to drain and fill it again just to visually inspect. If I have to wait then I'll wait, but shouldn't it be as easy as looking up the tranny code, or did they do Torsen and non-torsen using the same tranny codes? Like is there a list that Toyota has that can tell you?

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Postby timmey » Fri Feb 06, 2009 6:12 am

It turns out 734 is the JDM "Pre-facelift" tranny code seeing mine is a Pre-facelift, and I found this post. There is basically nothing else on the forum regarding that tranny code other than this post below and in Gary ST165's pic of his buddy's 91 engine tag:

eddie_gt4 wrote:SouthernViking, I guess that "E150F-734" is a tranny & diff code of some (all?) "pre-facelifted" JDM ST185's :oops:
but whether 734 = viscous LSC or Torsen, I don't know :shrug:

btw, other sources on i-net also mention such code...
jus go google with a "E150F-734"


Gary ST165 wrote:fact: my friends jdm feb 1991 st185 narrow body does not have a rear LSD. It has been inspected with a boroscope.

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Gary ST185: Your buddy's 91 narrowbody...is it open or torsen? I thought both are considered LSDs.

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Postby Razzo » Sat Feb 07, 2009 7:21 am

my 1990 narrow body jdm gt-four is open diff. Most gt-fours came with open diff, except a few rc models and 93+. i have a tranny code of e150
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Postby Corey » Sat Feb 07, 2009 8:55 am

Most gt-fours came with open diff, except a few rc models and 93+.


Except all RC's?
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