New source of Torsen T2 LSD's

Jeff Lange

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#1
I know some people have used the IS300 Torsen T2 in their MA70, and I just thought I'd share that there will likely be a more plentiful and potentially more common (though expensive at first probably) source for them in the new Scion FR-S and Subaru BRZ. Both of these are going to be equipped with the same LSD. :)

Jeff
 

nightrider760

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#2
some Is300 guys actually find to be an upgrade to use a MK3 lsd´s . All they do is ,swap out the internals... and they proceed to swap in the mk3 internals....
 

te72

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#5
I was always under the impression that Torsen diffs behave great, UNTIL you approach the limit of the inside tire, then you have a 1-way diff. Am I mistaken there? If not, why would one want to switch from a clutch-type to a Torsen? Better response perhaps?
 

3p141592654

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#6
I think you a re referring to the problem where the inner tire is airborne, then you have a problem because the TBR is usually only around 3 or so, and 3 x ~0 = ~0....

[wikipedia]
When a Torsen differential is employed, the slower-moving wheel always receives more torque than the faster-moving wheel. The Torsen T-2R RaceMaster is the only Torsen to have a preload clutch. So, even if a wheel is airborne, torque is applied to the other side. If one wheel were raised in the air, the regular Torsen units would act like an open differential, and no torque would be transferred to the other wheel. This is where the parking brake "trick" can help out. If the parking brake is applied, assuming that the parking brake applies even resistance to each side, then the drag to the airborne side is 'multiplied' through the differential, and TBR times the drag torque is applied to the other side. So, the ground side would see (TBR X drag torque) minus drag torque, and hopefully that can help restore progress either forward/backwards. In Hummer/HMMWV applications, there are both front and rear Torsen differentials, so the use of the main brakes will operate this "trick" on both axles simultaneously.
 

Poodles

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#7
Yeah, it makes the torsen a bit odd when driven past the limit. They're amazing up until that point though :)
 

PureDrifter

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#8
(very) generally speaking:

torsen=better for circuit driving/mild autocross/mild drag
clutch type (1.5 or 1way, ala turbo stock lsd)= better for drag, good for autocross/gym/beginner drifting
clutch type (2-way)= best for drifting (arguably), not well suited for circuit driving.
spool/welded diff= good for drifting, sometimes good for drag.

I'll probably be looking for an IS300 torsen at some point.
 

1StTurbo

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#9
Does anyone have a picture of the inside of a Torsen? I am trying to see if that's what i really have or another stock LSD
 

Zazzn

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#10
Hrm, sorry to bring this up from the dead, I'm about to have the Wier Max performance kit added to my LSD, but now seeing this I'd MUCH rather a torsen, as I do very limited drag racing in my mk3 and more less I love LOVE LOVE the way torsens drive day to day. Does the FRS Torsen unit work in the mk3 and is it a fairly simple swap? Does it hold up to power?
 

shipkiller

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#11
Hrm, sorry to bring this up from the dead, I'm about to have the Wier Max performance kit added to my LSD, but now seeing this I'd MUCH rather a torsen, as I do very limited drag racing in my mk3 and more less I love LOVE LOVE the way torsens drive day to day. Does the FRS Torsen unit work in the mk3 and is it a fairly simple swap? Does it hold up to power?
weren't you the one who convinced my cousin to buy that IS200 pumpkin for my mk3 diff?
 

Jeff Lange

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#13
Hrm, sorry to bring this up from the dead, I'm about to have the Wier Max performance kit added to my LSD, but now seeing this I'd MUCH rather a torsen, as I do very limited drag racing in my mk3 and more less I love LOVE LOVE the way torsens drive day to day. Does the FRS Torsen unit work in the mk3 and is it a fairly simple swap? Does it hold up to power?
I know this is an older post, but yes the IS300/FR-S/86/BRZ internals will all work in the A70 differential. Additionally, the ring and pinion sets are also compatible (though the pinion bearings are different).

Is it safe to assume that any aftermarket diff for the IS300 can be swapped out for the internals from the MK3 supra?

I'm asking since I was thinking about getting an mfactory helical LSD. They make one for the IS300.

http://www.tegiwaimports.com/mfactory-helical-lsd-lexus-is300.html
Yes, aftermarket diffs for those cars should work in an A70 as well.

Jeff
 

Kristian_Wraae

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#14
I got an answer from mfactory with the cryptic message: "the dimensions are different" when I asked the same question.

Now I'm thinking that they probably don't know what they are talking about and that they are most likely to say it won't work in order to avoid any issues.

But are there any theoretical senarios where the aftermarket LSD wouldn't work?
 

Jeff Lange

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#15
Highly unlikely, unless they have some sort of weird thing sticking off of it that will interfere with an A70 housing but not the JCE/GSE/ZN6 housing (they don't).

I would bet good money that it will fit and function just fine.

Jeff
 

Piratetip

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#16
Are the stub axles identical?
Circlip groove depth, spline count, spline dia?
I did look up the carrier bearings for both vehicles and they are the same, so the bearings should be a non issue.

Position of the face to bolt the ring to the same between both?
 

Kristian_Wraae

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#17
Highly unlikely, unless they have some sort of weird thing sticking off of it that will interfere with an A70 housing but not the JCE/GSE/ZN6 housing (they don't).

I would bet good money that it will fit and function just fine.

Jeff
Well we will find out - have ordered one..

Btw they also told me the diff was rated at 500 bhp. I would think that 500 bhp is less than the stock T2 will hold.
 
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Jeff Lange

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#18
Are the stub axles identical?
Circlip groove depth, spline count, spline dia?
I did look up the carrier bearings for both vehicles and they are the same, so the bearings should be a non issue.

Position of the face to bolt the ring to the same between both?
Spline count and spline diameter yes. The bolt face position is the same.

Circlip groove depth should also be the same, but I haven't personally verified it.

Jeff
 

Kristian_Wraae

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#19
Got the diff

DSCN0202.JPG

DSCN0203.JPG

Mfactory also confirmed that it would fit. They gave the wrong answer at first because they had looked up the JZA80 and not the MA70.

This ended up costing me $50 more than the used Lexus IS300 diff that is currently on ebay shipped to Denmark. So hopefully it will be as strong.
 

Kristian_Wraae

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#21
Finished the differential. All went in without any hassle.

DSCN0298r.jpg DSCN0307r.jpg DSCN0310r.jpg

Housing powder coated in HRE mat bronze and rear cover in steel grey.
 

GC89

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#26
is the cooler aftermarket? I believe you are correct, all the diffs I have do not have the horizontal cooling wings.

Very Nice
 

Piratetip

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#27
That cover was only available in EU region.
Toyota factory part, not aftermarket.
I have been trying to get an OEM one shipped over here to me in the states for some time.
I heard the extra cooling was supposed to be for extended high speed runs on the Autobahn, but can't confirm that.

Rear Cover
PN: 41181-14060
 
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Kristian_Wraae

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#28
is the cooler aftermarket? I believe you are correct, all the diffs I have do not have the horizontal cooling wings.

Very Nice
No it is stock Toyota. If I search on Toyodiy.com using my vin# I can find the part number. It is of course discontinued by now.

41607-14010 PIPE SUB-ASSY, DIFFERENTIAL HEAT

MCG258B.png

Also the 1991 version had a tighter diff than the 1992. I was told you could feel it on the 1991 when cornering with a very small radius.
 

Kristian_Wraae

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#29
That cover was only available in EU region.

I heard the extra cooling was supposed to be for extended high speed runs on the Autobahn, but can't confirm that.
Yes, I think you are right. My car was imported from Germany. I don't think all 1991 and 1992 had this.

I have a spare diff. But it is not as nice as this one. It has some damage to the cooling fins underneath the differential due to people jacking up the car using the diff to support the jack.
 

Piratetip

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#30
How bad is the damage on the rear cover?
You willing to sell me just that part?
I can weld aluminum so could repair it back to stock depending on how bad it is.
 

Jeff Lange

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#33
An air guide was mounted to the top of 86.5-92 European-spec cars.
A rear cover with the larger cooling fins was used added on some 89-92 European-spec Turbo cars.
An oil cooling pipe was used on some 90-92 European-spec Turbo cars.

For the rear cover and cooling pipe, specifically Euro-spec cars that came with catalytic converters (excluding Australia).

41191-14010 - Differential Upper Air Guide
90201-12020 - Differential Upper Air Guide Washers (Qty: 2)
41181-14060 - Differential Cover with Larger Cooling Fins
41101-14030 - Differential Case with Provision for Cooling Pipe
41607-14010 - Differential Cooling Pipe
41672-14010 - Differential Cooling Pipe Bracket
91651-61018 - Differential Cooling Pipe Bracket Bolt
41679-14010 - Differential Cooling Air Duct
90119-06380 - Differential Cooling Air Duct Bolt

The differential clutch packs and spring were changed as was stated, later differentials (90'ish) are sprung lighter to reduce noise.

Jeff
 

Piratetip

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#34
I have also seen late model LSD's change the friction / steel / friction order of the LSD clutch packs to Friction / Friction / Steel order. (Among other random combinations. Which reduces the effectiveness of the lockup. I heard at one point it was due to TSB's or customer concerns of chattering around corners.

Reminds me of what i saw on the MKII diff rebuild I performed. That clutch pack had zero steel plates, only friction plates. Essentially a useless LSD until it's modified.
Wonder what the midset was on that vehicle launch, since the LSD is built to accept alternating steel plates.
 

Jeff Lange

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#35
I'll post up the TSB when I remember if you're interested.

I wonder what the COF for friction plate on friction plate is vs. friction plate to steel plate.

Jeff
 

Piratetip

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#36
Yeah post it up.

COF won't be a factor. Steel plate is splined to side gear, friction plate is splined to case.
If they aren't alternating steel / friction they won't be sliding past each other. Just sitting stationary as one. (The side by side identical plates)

If they aren't alternating every plate, it's just a matter of a reduced number of friction surfaces doing work.
Reduces the breakaway and dynamic torque holding ability.
 

Jeff Lange

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#37
Right, of course. Brainfart.

Here's the TSB, it really feels like they neutered the LSD when they did this. (Though they did increase the number, total stack height increased by 2.4 mm per side, the spring rate reduction is huge).

I'd like to know the comparison between the torque between the two (breakaway and dynamic).

The change happened in midlate 1990 model year production (May, 1990), so all 91-92's have the updated LSD clutch arrangement.


Jeff
 

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Piratetip

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#38
Ah interesting.

I will have to measure the different stackups the next time I rebuild one.
Will let you know.
 

Piratetip

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#39
For those interested I had a look at all the MFactory products that would fit our application:

Helical LSD
PN: MF-TRS-05GT86

This is the LSD that the OP installed in this thread.

They also have 3 different styles of clutch pack LSD's.
Metal Plate LSD
1.0 Way

PN: MF-TRS-10GT86

1.0 / 1.5 Way
PN: MF-TRS-10GT86A

1.5 / 2.0 Way
PN: MF-TRS-10GT86B

For those not familiar with these terms its the shape of the cross shaft and corresponding pressure rings that interact with each other.
Can change the behavior of the lockup on decel and accel separately depending how the components are setup.
Essentially a wedge shape forces the pressure rings apart for more lockup or a flat face does not.
Multiple combinations of this are available.

Not sure if Mfactory LSD's are like CUSCO where you can just take them apart and rotate the cross shaft to change the behavior.

Image explaining 1.0 / 1.5 / 2.0 attached to post.
 

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suprarx7nut

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#40
Right, of course. Brainfart.

Here's the TSB, it really feels like they neutered the LSD when they did this. (Though they did increase the number, total stack height increased by 2.4 mm per side, the spring rate reduction is huge).

I'd like to know the comparison between the torque between the two (breakaway and dynamic).

The change happened in midlate 1990 model year production (May, 1990), so all 91-92's have the updated LSD clutch arrangement.


Jeff
Super cool to see this, Jeff. Do you have other TSBs that apply to the MK3 you could share? I'd LOVE to catalog all of them and post them up on my site (If that's ok). I work in manufacturing and seeing this sort of bulletin in a topic I actually care about is soooo much more fun than what I usually work with.

Piratetip: as always, awesome info, thanks.