Clutch LSD => Torsen LSD

[Hybrid]

Howdy,

I currently have a 4:3 Clutch LSD in my car (MA70 Supra) , which I want to remove and replace with a Torsen LSD.

I have the Torsen LSD which I purchased from forum sponsor Import Bitz (plug plug ). It is out of a JZA70 Supra. I purchased it complete in the original housing.

I have heard people say however that the Torsen's run longer side shafts than the Clutch LSD's. Can someone confirm this?

If this is the case I presume I will be unable to (as I had hoped) just drop the Clutch LSD housing off & bolt the Torsen LSD housing in?

Failing this I gather the alternative is to remove the guts of both Diff housings and place the torsen gear into the clutch LSD housing?

Any advice would be fantastic.

[07XTC]

You diff is a G series supra diff right? I just pre-fitted (test fitted) a G series Torsen LSD center into a G series turbo supra diff housing that used to have a clutch type LSD center in it. The splines, crown wheel and pinion all line up perfectly. So I am unsure if this is true or not? I know that the clutch type LSD was from an import car.

I also found that a hilux (live axle diff) center is interchangable too. Cause I just did a test fit of the same G series torsen into the hilux/hiace diff housing and everything lined up perfectly (this was after I was told that the diff center from a supra needed machining down first to be able to fit a hilux).

Hope this helps you out?

Did you end up getting your diff from John yet? Or are you still waiting on it? How much did you pay for the Torsen if you dont mind me asking? I just sold my torsen in perfect condition (almost new) for $500 inc.postage.

James

PS: Does he have anymore of them coming or in stock? If you know he does (dunno if he updates the website regularly) then let me know, cause there are two other people that missed out on my sale that are still chasing them. Thanks

[Sprinterboy]

what do you use the carf for? drag, track? daily?

I'm personaly not a fan or the torsen type

[kirk]

What's wrong with Torsen centers? (Sorry, researching wether or not to get one)

[07XTC]

Depends on what your after. For daily driving, drag racing and a good all round car nothing can beat a torsen. For drift a good clutch type is the answer. This is mainly because of how the torsen works. Do a search on the forum here under "Torsen Diff" and you will see many discussions (some of them heated in the decision of what to choose) and you should be able to find a LSD to suit your purpose.

[Norbie]

The only real problem with a torsen is you lose traction when you lift a wheel. For some circuit racers this can be a bad thing, but for 99% of street cars you'll never lift a wheel, and even if you do you won't be accelerating at the same time, so it doesn't matter.

I've heard of quite a few OEM Toyota torsen diffs exploding when used for drag racing, so they're probably not suitable for that application - I don't know if this applies to all torsens or just Toyota ones though.

[oldcorollas]

aiui, all torsens have a bit of a power limit... i can't remember if it was around 600hp or 600kw... second sounds a bit high...

basically due to mechanical strength of the internal gears themselves...and the housing holding them together... so yeah, they are a bit limited in that respect, but as for distribution of torque, it's hard to beat them...
clutch pack is just a sloppy locker... but does tighten up with force also. a bit..

[Cameron_Datto]

Torque Biasing Differentials Versus Limited Slip Differentials

So what is a Torque Biasing Differential and how does it differ from a Limited Slip?
First an understanding of what is meant by a torque sensing differential or torque bias differential. To help understand torque biasing differentials I'll define a few new terms:

Torque Handling Capacity - This is simply the amount of axle torque that a tire is able to transmit to forward acceleration without slipping.

Torque Handling Capacity Difference - When a car is going around a corner weight transfer will lighten the inside wheel, limiting the amount of axle torque that the tire is able to transfer to forward acceleration. In this state there is a torque capacity difference between the inside tire and the outside tire.

Torque Bias - This is the amount of torque across the differential required before it will allow differential action (one wheel to spin faster than the other).

Torque Biasing Differentials
There are two situations where the differential biasing differential will differentiate. The first is under low power going around a corner where torque bias is relatively low (almost no torque input) and there is enough traction on the inside tire (due to scrubing) compared to the outside to overcome the low torque bias. The second situation is usually under heavy throttle (or rain) and cornering where the inside tire will not be able to transfer the axle torque to the ground. In this situation the outside wheel has a higher torque handling capacity than the inside wheel. When the torque handling capacity difference is greater than the torque bias the differential will differentiate allowing the inside wheel to spin.

With a torque sensing differential the goal is pick a torque bias which prevents wheel spin but limits power on induced understeer.

Difference between Torque Bias and Limited Slip
A limited slip differential has a high initial torque bias (sometimes called preload) then VERY gradually increase (linear) as input torque is applied. On the other hand a Torsen or Tru Trac has almost no initial torque bias but the torque bias increases at a much faster rate (also linear) as input torque is increased.

As an example - A Dana 60 limited slip has an initial torque bias of about 400 ft lbs. Meaning that if you were to jack up both wheels and had one person hold one wheel and another try to spin the other. The person trying to spin the wheel would have to apply 400 ft lbs to make it spin. As input torque is applied (you step on the gas) the torque bias increases very gradually to about 900 ft lbs before one tire will slip.

Now a Torsen (and Tru Trac) has about a 0 torque bias with zero input. So if you were to jack up both wheels and try to spin one while holding the other it should be almost effortless. However if you increase the input torque to say 1000 ft lbs, with a Torsen with a 3.5:1 torque bias you now require 555 ft lbs across the differential before it will differentiate.



1000 ft lbs therefore:
3.5:1 ratio, there 4.5 total
1000/4.5 = 222 on one wheel, 777 on the other
777 - 222 = 555 torque bias.

Now increase the input to 3000 ft lbs and the torque bias is 1667 ft lbs.

Another advantage of the Torque Biasing differential is that when you lift off the throttle you have almost zero torque bias so less tendency to understeer. Drawback is that when you stomp on the gas it will be less stable (without preload).

The limited slips also wear and as they do the torque bias they can apply quickly drops away severely limiting their effectiveness.

The TracTech Tru Trac is another torque biasing diff, biasing ratios between 2.5:1 and 3.5:1. The Tru Trac is generally considered not strong enough for high horsepower race cars. Then there is the Gold Trac which is the only torque biasing differential that is available with preload. Preload is an initial torque bias. This allows the unit to bias with light throttle and makes for more stable corner exits. The preload is adjustable. The Gold Trac works the same as a Torsen or Tru Trac, the only difference being that it has adjustable preload (a good thing).

Below is an email exchange with a Torsen engineer to determine the best torque bias to choose for the test car. There is only one torque bias available for the Ford 9".


quote:


-----Original Message-----
From: Greg Carter
Sent: Wednesday, June 07, 2000 1:15 PM
To: '[email protected]'
Subject: Choosing TBR for race car

Hi,

I am trying to calculate the ideal torque biasing ratio for my
application:

Ford 9"
Watts link, approximately 12" from ground pivot point. No rear
sway bar.
Rear Track width 60".
Road Race car.

So assuming car mass over the rear as 1 unit, 1.0 u for
coefficient of friction, car going around a corner, I have come
up with the following
ratio:

1/2 + 1/5 for outside tire
1/2 - 1/5 for inside tire

1/2 comes for the fact that 1/2 the weight of unit 1 is applied
at each wheel, 1/5 is the torque at the wheels to counter the
moment about the c of g (the mass of unit 1, 1 foot off the
ground). Distance between the two
wheels is 5 feet, so need 1/5 the force.

So:
.7/.3 ~ 2.3:1 TBR. Would a 3.5:1 work best, to account for
less than ideal traction (bumps) etc?

I don't have the actual car weight as it is still being built. The
engine develops approximately 800 ft lbs of torque.

Thanks for any help.

Greg Carter


Zexel Torsen Engineer reply

quote:


-----Original Message-----
From: xxx
Sent: Wednesday, June 07, 2000 2:07 PM
To: 'Greg Carter'
Subject: RE: Choosing TBR for race car


We've found that normally a bias ratio between 2.8 and 4.0:1
to be best for most race cars. The key is keeping the inside
rear wheel firmly planted on the track. If it does so with out
any major traction loss from unloading (obviously, the weight
transfer will pick it up some), then the lower end of the range
will work. If, like a lot of Mustangs or Camaros, that wheel
gets
picked up quite a bit, then a higher bias is needed to
overcome the loss of traction on that lifted side. Also, a
higher bias will always send more torque to the high traction
side, so that maybe beneficial in and of itself.

If the bias is too high, however, the differential will tend to
act much like a locker, which induces understeer in turns. For
reference, by too high, I mean 5 or 6:1 or higher. Ultimately,
though, the bias ratio is already chosen for you (assuming
you intend to use a Torsen). The 9" differential we make is
about 3.5:1, and doesn't come in other ratios. This should
work quite well for most race cars.


My question on torque ratings

quote:


-----Original Message-----
From: Greg Carter
Sent: Wednesday, June 07, 2000 3:00 PM
To: xxx
Subject: RE: Choosing TBR for race car


Well that sure makes selection easy! One other thing, just
want to check on the torque limits for the unit.

Assume a CoF of 1.0 and almost 100% of the weight transfers
to the rear at max acceleration I would need it to handle:

3000 lbs x 1.0 x tire radius (26"/2) = 39000 in-lbs or 3250
ft-lbs of output torque to break the tires free in ideal traction
conditions.

Using a safety factor of 2 (dumping the clutch, shifting gears,
yahoo driving, etc.) I would like to have a unit that could
handle 6500 ft-lbs.

The engine produces 800+ ft-lbs of torque x 3.06 (1st gear) x
3.5 (rear end) = 8570 ft-lbs, so the max torque is definitely
limited by traction.

Will the unit withstand this amount of torque?

Thanks again.

Greg Carter
Entrust Technologies - http://www.entrust.com


His reply

quote:


-----Original Message-----
From: [email protected]]
Sent: Wednesday, June 07, 2000 3:54 PM
To: 'Greg Carter'
Subject: RE: Choosing TBR for race car


Actually, the way the differential is rated is short duration
torque (engine torque X gear ratios), plus impact torque,
which adds a "shock" factor for clutch dumps, etc. Impact
torque is an instantaneous torque spike that occurs from a
sudden loading. The factor used is something like 3 or 3.5
(depends on a number of things), although impact IS
ultimately limited by wheelspin. If you could prevent
wheelspin, the impact torque would be short duration X 3
(8570 X 3 = 25710 lbft). Eeek, that's high. Fortunately, its
limited by wheelspin. And, of course, your assumptions are
probably a worse case then actual. If 6500 lbft is what your
after (because of the wheelspin), your in luck. The diff can
withstand about 9000 lbft with no trouble. Our testing has
shown that the pinion shaft will fail before the
diff does (we've seen them fail around 8800 lbft). So, to make
a long story short, it should work, unless you manage to
dump all your torque into it with no wheelspin...

[oldcorollas]

The diff can
withstand about 9000 lbft with no trouble. Our testing has
shown that the pinion shaft will fail before the
diff does (we've seen them fail around 8800 lbft)...

right..... that should do it.. but that is a 9", and i guess not many toyotas will be 3000lb and be making 800ft-lbs of torque.....

so what are the F series tru-tracs rated at?

[Hybrid]

You diff is a G series supra diff right? I just pre-fitted (test fitted) a G series Torsen LSD center into a G series turbo supra diff housing that used to have a clutch type LSD center in it. The splines, crown wheel and pinion all line up perfectly. So I am unsure if this is true or not? I know that the clutch type LSD was from an import car.

I also found that a hilux (live axle diff) center is interchangable too. Cause I just did a test fit of the same G series torsen into the hilux/hiace diff housing and everything lined up perfectly (this was after I was told that the diff center from a supra needed machining down first to be able to fit a hilux).

Hope this helps you out?

Did you end up getting your diff from John yet? Or are you still waiting on it? How much did you pay for the Torsen if you dont mind me asking? I just sold my torsen in perfect condition (almost new) for $500 inc.postage.

James

PS: Does he have anymore of them coming or in stock? If you know he does (dunno if he updates the website regularly) then let me know, cause there are two other people that missed out on my sale that are still chasing them. Thanks

Yep the torsen is a g-series in a A70 Supra housing... I have an MA70 Supra that has a clutch LSD at the moment.

My question I guess is... is the Torsen housings and clutch lsd housings identical or are there slight differences that could cause me issues when I take the clutch lsd (including the housing) out of the car and whack the torsend lsd (including the housing) into the car.

I have the torsen yep, cost me about $600 + shipping.

[SillyCarS]

Hey mate,

ws this problem ever resolved? cos i have the same one

i have a torson lsd (centre only, no housing, no ratio) from a supra and i want to put it into a g series diff, but im told its ot as simple as just pulling apart an open centre and swapping the bits over.

PLEASE HELP ME!!!!!

craig

[Hybrid]

Hey mate,

ws this problem ever resolved? cos i have the same one

i have a torson lsd (centre only, no housing, no ratio) from a supra and i want to put it into a g series diff, but im told its ot as simple as just pulling apart an open centre and swapping the bits over.

PLEASE HELP ME!!!!!

craig

Hi Craig,

When I did the swap I just unbolted the complete clutch lsd (housing and all) and bolted up the Torsen (housing and all).

So unfortunately my situation was far less complicated than yours as it ended up to be just a straight swap out. Took about 1 hr from start to finish to complete.

[SillyCarS]

i was afraid you would say that, i might just have to buy the one in the classies and fix it up.

Thats if its the right one


cheers

craig

[Hybrid]

My 4:3 clutch LSD (complete with housing) is available for sale, and I am in SA. It is just in my shed as a spare incase I ever blew up the torsen.

I'd maybe ring a few dif places first though here in SA, and see what they say about getting the centre you have into the housing you have. You need to used the hilux housing don't you rather than a supra one?

[SillyCarS]

yeh id like to stick with a torson as its going to be primarily street use.

im not sure about the housing

im ringing around now, i'll let you know how i go

just in case PM about the housing you have and price and etc


thanks

craig