Torque Biasing Diffs

[Roverworks Canberra]

Limited Slip Diffs are quite a common fixture for Rovers, but there's a much better option!

Torque Biasing Diffs behave like normal open diffs around town, with no difference to driveability. They also do not drag wheels and wear tyres out. If a wheel slips, they automatically shift torque away from the slipping wheel to the one that is not slipping, without you even knowing it has happened. It’s all in the construction of the diff; there is no electronic wizardry or anything extra to gum up full of mud and fail on you. They still leave about 25% of the torque going to the slipping wheel, so that when it grabs it is ready to grip and move straight away. As soon as the slipping wheel grips, it has 100% of the torque back to pull you out of the situation. These are great for what most people experience in their four-wheel driving adventures – a bit of mud, sand, snow and some loose surfaces on hills etc.

Read more here:
Torque Biasing Differentials (http://roverworks.com.au/news/torque-biasing-diffs-land-rover-discovery-12-defender/)

Agree?

[Gerokent]

It would be nice if they explained how they work as there is a million different designs of "torque biasing" diffs out there.
As for their description of LSDs "The technology uses a slightly different philosophy to limited slip diffs, which allow a wheel to slip so far before stopping"
which is false. An LSD does not allow a wheel to slip then stop, it stops a wheel from slipping, then allows it to spin.
I would be wary of those who spin you a yarn ;)

[workingonit]

Ashcroft Transmissions (http://www.ashcroft-transmissions.co.uk/limited-slip-differentials.html)

[djam1]

I have never found Limited Slip Diffs common for Rovers!

I have an Ashcroft ATB and consider it a good thing but a locker its not.


Limited Slip Diffs are quite a common fixture for Rovers, but there's a much better option!



Agree?

[Drover]

With a Torque Baising diff it all "beer n skittle's" until you lift a wheel.....and then it's all over red rover ! :o

[PAT303]

With a Torque Baising diff it all "beer n skittle's" until you lift a wheel.....and then it's all over red rover ! :o

Well if thats the case how does the traction control work?,I could cross axle the L322 and the TDCi and both kept truckin',the ATB should make the TC better shouldn't it?. Pat

[TonyC]

Well if thats the case how does the traction control work?,I could cross axle the L322 and the TDCi and both kept truckin',the ATB should make the TC better shouldn't it?. Pat

Yep and that's why folks say ATBs and TC is a match made in heaven.

Not that I have ether :angel:

The other way is left foot braking, but that would require driver input and skill, and that's just not the modern way :D

Tony

[Drover]

Braking !

mmmmm.....That will help with traction & momentum.

The point is that anything other than lockers is a compromise.

If TC is such a terrific thing....then why is there even a market for lockers/TB's/LS centres.........

[TonyC]

Braking !

mmmmm.....That will help with traction & momentum.

A ATB needs some resistance to work. If there is no traction on one wheel then they make no difference. That's why they work very well with ETC, or if you don't have ECT then some braking can provide that resistance.


The point is that anything other than lockers is a compromise.

Every thing is a compromise, full manual lockers included, it just depends on the compromise your prepared to put up with.
For me it's open diffs, take away the money issue and it would be a pair of full manual lockers.

That doesn't mean that's best for everyone.


If TC is such a terrific thing....then why is there even a market for lockers/TB's/LS centres.........

ECT is free once you have ABS, the others all have there up and down sides.

Tony

[joel0407]

The point is that anything other than lockers is a compromise.


What a total load of rubbish. I proved that wrong just the other weekend.

With Locked diffs, it's hard to steer. With traction control you maintain full steering which is handy on a technical climb with wheels lifting. A Prado with a rear locked had 5, 6 maybe more goes and failed to get up the easy hill but I made it up without too much trouble in the Disco. Then a 4 inch lifted, front and rear locked Patrol had a go at the steeper and harder hill. The first time he spun all 4, then he near lifted the front and the front started to slide sideways at the same time. We thought he was goes to spin around and roll it down the hill. Third time he snapped the tail shaft. Again the Disco went up with little drama.

The only time I have had trouble is in very deep mud when I have already started to spin before the traction control kicks in and then it's too late. ATB diffs would fix this.

The only down side to Traction control is it's reactive. It doesn't work until you have lost traction and from my experience when a wheel starts to lift then all the weight has to be on the opposite wheel and that means it's not usually struggling for traction. It's when all wheels are still on the ground and the surface is slippery that traction control fails but then that's exactly the situation that a ATB needs to work.

Happy Days.

[Disco Muppet]

Uhm, there's a market for lockers because a) some people want them and b) some people don't have traction control.
Modern LR traction control systems don't just brake the spinning wheel, the redirect the power to the other wheels.
ATBs plus CDL plus TC = great guns.
Sure, full lockers have their benefits, but so does the above.
All in all it comes down to a) where you want to go, b) how much you want to spend and c) how you personally like to do things.
TBH I don't understand why we're having this argument again, each side has its pros and cons and has been done to death not just here but all over teh interwebz.
I'm going for ATBs because they suit my budget, my driving style, and where I'm likely to take the vehicle.
Simples :)

[isuzutoo-eh]

Limited Slip Diffs are quite a common fixture for Rovers, but there's a much better option!

Torque Biasing Diffs behave like normal open diffs around town, with no difference to driveability. They also do not drag wheels and wear tyres out. If a wheel slips, they automatically shift torque away from the slipping wheel to the one that is not slipping, without you even knowing it has happened. It’s all in the construction of the diff; there is no electronic wizardry or anything extra to gum up full of mud and fail on you. They still leave about 25% of the torque going to the slipping wheel, so that when it grabs it is ready to grip and move straight away. As soon as the slipping wheel grips, it has 100% of the torque back to pull you out of the situation. These are great for what most people experience in their four-wheel driving adventures – a bit of mud, sand, snow and some loose surfaces on hills etc.

Read more here:
Torque Biasing Differentials (http://roverworks.com.au/news/torque-biasing-diffs-land-rover-discovery-12-defender/)

Agree?



Disagree. Something doesn't sound right.
Shouldn't it be 25% of the torque goes to the axle with traction and 75% lost to the slipping wheel? Happy to be corrected...

As has been said by others, LSDs of the friction plate type aren't common in Landies-you might be thinking of Patrols. ATB diffs from Eaton (Trutrac) and Ashcroft have been around for years. I have had two Ashcroft ATBs now, though one now sits forlorn in a box in my parts stash. I'm very happy with the one in my County, when mixed with the Detroit in the rear gives a lot of traction and controllability.
What brand are you installing?

[Tusker]

Disagree. Something doesn't sound right.
Shouldn't it be 25% of the torque goes to the axle with traction and 75% lost to the slipping wheel? Happy to be corrected...

snip



Mark I think you're on the money. When I looked into these, those sourced via Truetrac were 3:1, and those from Quaife were 4:1. Again I'm happy to be corrected if my hazy memory proves wrong.

And as has been pointed out in an earlier post, lift a wheel and 3 or 4x 0 = 0.

Regards
Max P

[Dorian]

Disagree. Something doesn't sound right.
Shouldn't it be 25% of the torque goes to the axle with traction and 75% lost to the slipping wheel? Happy to be corrected...

snip


Well it's time to smile.:) As long as the slipping wheel has some traction, then the slower moving wheel gets biased with more torque.

Have a look at the truetrac video, my understanding of it's operating principle, is that the wheel that's moving faster will push the "idler" shaft ( these are equivalent to the bevel gears mounted on the cross pins of a standard diff) over to the slower turning wheel. It does this because the helical design of the gear sets on the "idler" and sun gears (end of axles) causes a side force when the two axles spin at different rates.
As this happens the idler gear binds up on the side of the "hemisphere" (it's really a cylinder) over on the slower moving wheel. When the idler shaft binds on the side of the hemisphere then torque is biased onto this wheel . The idler shaft stops turning in it's pocket and creates a sort of lock.

"So if it locks then why doesn't it send all of the torque over to that wheel?"
It can only bias a portion of the torque cause it needs the pressure of the faster wheel to keep the idler shaft against the side of the hemisphere, the ratio will depend upon the angle of the helical cut of the sun gears and idler gears.
So if the wheel starts spinning in free air rather than slipping there is not enough pressure on the helical gears of the idler shaft to keep it over on the slower moving wheel and hence form the lock against the side of the hemisphere
That's why ATB's and traction control work so well together. While both wheels are on the ground , the ATB will prevent the wheel with less traction from spinning, yes it will slip but not spin wildly, this will delay TC coming on, and TC will divert power away from the car. When one wheel lifts and starts spinning then TC will kick in but the ATB will start working, this in turn will reduce the torque going to the wheel that the TC is holding meaning that the TC drains less power.

There may be some finer points I have missed but I'm pretty sure that the gutz of it.

Cheers Glen

[voltron]

Ok, Im a newbie and have been wandering if I should go lockers, or ATB. So because I have TC on my TDci the ATB is the best option to compliment my TC??

I thought i read somewhere all you guys were saying TC is bad for the axles or something I can't remember. But TC was BAAAAD!

Cheers.

[inside]

I thought i read somewhere all you guys were saying TC is bad for the axles or something I can't remember. But TC was BAAAAD!
You'll read a lot of things on this site and a lot can be rubbish. Make an effort to sift through all the information and make your own decision.

[chook73]

Ok, Im a newbie and have been wandering if I should go lockers, or ATB. So because I have TC on my TDci the ATB is the best option to compliment my TC??

I thought i read somewhere all you guys were saying TC is bad for the axles or something I can't remember. But TC was BAAAAD!

Cheers.

Frankly nothing "compliments" TC if you can afford them and are deciding between ATB and Lockers for me its lockers every time.

This video shows and explains the difference between open diffs, TC and lockers well worth a look.

Air Locker vs LSD vs Traction Control Part 1 - YouTube

[joel0407]

Frankly nothing "compliments" TC if you can afford them and are deciding between ATB and Lockers for me its lockers every time.

This video shows and explains the difference between open diffs, TC and lockers well worth a look.

Air Locker vs LSD vs Traction Control Part 1 - YouTube (http://youtu.be/C2wkW05Pc6c)

Video shows Toyota traction control which is probably the worst out there. The D2 traction control is a little better even thought it's about 10 15 years old but that also makes it a bit less reliable (3 amigos). Video is also sponsored by ARB who are selling, what do you know ARB air lockers.

I drive a 200 series, that is less than 12 months old, at work with Toyota TC and it's rubbish. The brakes grab too hard and lock the spinning wheel, that drives all the power/torque to the opposite wheel which immediately spins because the power transfer isn't smooth. Then as the lifted wheel has just been locked because it has been braked by the TC, TC releases the brakes because the wheel isn't turning then the vehicle lurches backward.

My D2 has none of these traits. One thing it will do, if you go dead slow, there is a pause as the lifting wheel spins maybe a 1/8th of a turn while the TC brakes that wheel. As long as you are going walking pace, the pause isn't enough to loose too much momentum.

What's your experience with TC, Chook 73?

[joel0407]

This gnarly hill a lifted 80 series and a lifted Prado with a rear locker couldn't get up.

https://vimeo.com/105476118

Then this hill a 4 inch lifted Patrol with front and rear lockers couldn't get up.

Past the Nissan on Vimeo

Happy Days

[Blknight.aus]

The very early traction control was bad, and was known to break the front axle.

Landrovr softened it up a bit and all's good.

A torque biasing diff transmits extra torque away from the wheel that is spinning at a given ratio. If the wheel that is spinning has 20nm of reaction torque on it then with a 3:1 ratio torque biasing diff the wheel that has the most grip gets 60nm of drovi g torque.

This is different to an lsd in that an lad will allow a certain slip ratio before it begins to hook up the torque to the other wheel but there is no requirement for the wheel that spins to have any reaction torque.

With a torque biasing diff traction control becomes fantastic imho better than lockers because you can still steer and you don't break the traction of the wheels still on the ground like you can with a locker or an Lsd.

While a locker and a Lsd force drive by limiting the amount of difference in rotational speed the don't provide any method of torque release which means if you try to stick more torque down than you have traction to support then the wheels will still break free and that means loss of traction. Loss of traction = stuck or sliding.

With a torque biasing diff you can still cross axle and hang up with diagonal opposite wheels in the air, your just a lot less likely to and with traction control doing it's bit then you e always got some reaction torque on the wheels.


Just. my two cents.

[Sitec]

It would be nice if they explained how they work as there is a million different designs of "torque biasing" diffs out there.
As for their description of LSDs "The technology uses a slightly different philosophy to limited slip diffs, which allow a wheel to slip so far before stopping"
which is false. An LSD does not allow a wheel to slip then stop, it stops a wheel from slipping, then allows it to spin.
I would be wary of those who spin you a yarn ;)

Here you go....... http://m.youtube.com/watch?v=lZmsY2YvVsc


And IMO a Detroit in the rear and a Trutrac Torque Biasing Diff in the front makes for the best 'fit and forget' but very capable off road setup. Ran it in my competition off roader, the last defender, and when I find a way I'll b fitting a Trutrac in the front of the 101!!

[Blknight.aus]

Here you go....... http://m.youtube.com/watch?v=lZmsY2YvVsc


And IMO a Detroit in the rear and a Trutrac Torque Biasing Diff in the front makes for the best 'fit and forget' but very capable off road setup. Ran it in my competition off roader, the last defender, and when I find a way I'll b fitting a Trutrac in the front of the 101!!

You need the imperial 8ha unit to suit the center you have (based on ratio) from memory you have to pull it apart rotate a bu ch of components left for.right and then put it back together.

I've only looked into it, I haven't done. One yet.

[Sitec]

You need the imperial 8ha unit to suit the center you have (based on ratio) from memory you have to pull it apart rotate a bu ch of components left for.right and then put it back together.

I've only looked into it, I haven't done. One yet.

I'm running 3.54:1 ratio, with centers out of a 110 rear.. The Trutrac will fit no prob, just have to get the gears broached out to accept the giant 101 shafts..

[chook73]

Video shows Toyota traction control which is probably the worst out there. The D2 traction control is a little better even thought it's about 10 15 years old but that also makes it a bit less reliable (3 amigos). Video is also sponsored by ARB who are selling, what do you know ARB air lockers.

I drive a 200 series, that is less than 12 months old, at work with Toyota TC and it's rubbish. The brakes grab too hard and lock the spinning wheel, that drives all the power/torque to the opposite wheel which immediately spins because the power transfer isn't smooth. Then as the lifted wheel has just been locked because it has been braked by the TC, TC releases the brakes because the wheel isn't turning then the vehicle lurches backward.

My D2 has none of these traits. One thing it will do, if you go dead slow, there is a pause as the lifting wheel spins maybe a 1/8th of a turn while the TC brakes that wheel. As long as you are going walking pace, the pause isn't enough to loose too much momentum.

What's your experience with TC, Chook 73?

Frankly I have never been a fan comparing completely different vehicles setup differently with different drivers with different air pressures, I can assure you that my defender with the correct air pressures and lockers engaged will walk anywhere (and go a heap further) your D2 with TC will lurch up. But then your D2 with the correct air pressures and the correct line will probably lurch up somethings my defender with lockers, a bad line and the wrong air pressures wont make it up...... ;)

My experience with Traction control is I fitted lockers. Put very simply TC in my 2009 Defender used to work by breaking the wheel that had lost traction to enable the differential to send the power to the wheel that had traction. This meant that at some point the wheel which had had the brakes applied would regain traction moving at a different rate (possibly with the brake still applied) putting strain on the driveline. I have seen many cases where this has resulted in broken CV's or half shafts.

I might be missing something here but taking it back to basics and putting the ATB aside for just a minute, the basic principle is that Traction Control brakes the wheel that has lost traction but has all of the drive..... at this point the differential by way of principle has already transferred all of the drive to the wheel without traction... now can someone please explain to me how this aids forward momentum? It doesn't matter how power gets transferred after this point, be it by differential only or by computer the damage has been done, you have lost traction with one wheel and power has already been transferred away from the wheel with traction, from this point on its reactionary.

Ok now I will admit that I dont have much experience with Torque Biasing Diff's however using Bliknight's post as an example, which is my understanding "A torque biasing diff transmits extra torque away from the wheel that is spinning at a given ratio. If the wheel that is spinning (and at this point travelling at a different speed) has 20nm of reaction torque on it then with a 3:1 ratio torque biasing diff the wheel that has the most grip gets 60nm of drovi g torque."

In this example a wheel has broken traction so the ATB is transferring some power away from that wheel but it needs the 1/3 power to keep the wheel spinning to keep the ATB engaged so in principle the ATB relies on the wheels travelling at different speeds, one wheel has to loose traction for the ATB to work. Your now spinning wheels up a track to make your truck's diff work properly.....:angel:

Admittedly this is better than TC by a long shot but back to my original post I fail to see how this can "compliment" TC, you have already lost traction for it to work and as soon as that wheel lifts even a millimetre the ATB is redundant (you spent how much?) Now the TC is back applying the brakes to a wheel in order to transfer the drive back to the other wheel that has already had all of the drive removed from it.

If your vehicle is applying the brakes to a wheel which has lost traction when that wheel re-gains traction it is travelling at a different speed to everything else, I fail to see how this is a good thing. Sure its better than nothing but its not a good thing......

So then we have lockers, they dont wait until something breaks traction to transfer drive, they distribute the drive equally between the four wheels and keep them turning at exactly the same rate no matter the state of traction. Lift a wheel and you still have 75% of the drive to the vehicle you had previously and nothing is trying to prevent your forward momentum by applying brakes or transferring torque to compensate for wheels slipping. If both your rear wheels loose traction in the mud then they are equally trying to regain traction. Sure its a bit harder to steer with lockers, you need to concentrate and think ahead but in my experience the lockers allow me to take obstacles with a lot more care to both my truck and the track.

My theory is I spent money on lockers so I am going to use them. I have nothing to prove by trying to get up/through/over an obstacle before I switch on the lockers, by using lockers I am looking after my truck and the track so why not use them. You only need to cross the Simpson at the moment to see the damage to tracks that is done by incorrect air pressures and Open diffs and TC with muppets giving it the berries.....

It would be interesting to know how many ATB's Dave Ashcroft sells to lockers, I would bet that his lockers outsell his ATB's by a country mile despite them costing $350 more....

[djam1]

I have an Ashcroft ATB in the front of a 2002 Defender that has traction control.
I purchased it predominantly to get rid of the Rover Diff Centre

While its a good thing on high speed low traction dirt roads its performance off road relying on the traction control is nothing like those who theorize about it on forums suggest.
To be honest the performance is a bit disappointing! before everyone jumps in and says how a 2002 Defenders traction control is not good enough.
When I researched it and in my time I was testing I was using the same Wabco ECU that the Puma was using.
Driving with my foot into it to bring on enough wheel spin for the traction control to make a real difference isn't my driving style.

Unless I am in a hurry anyway

[joel0407]

I agree with you "Chook 73" that TC is reactive and lockers are proactive. I think I said it in an earlier post that it's a down side in mud as by the time TC works then traction is lost and it's too late but ATB fixes this.

I think you are wrong in the way you are thinking a wheel has to be spinning or operating at a different speed to the opposite wheel for the ATB to be working. ATB will work on load not rotational speed so if one wheel is in mud and the other on bitumen then most of the torque will be sent to the wheel on the bitumen and the wheel in the mud wont spin providing it has enough traction to hold 1/3 of the torque being sent to the other wheel.

ATB diffs are proactive until a wheel gets less load than 1/3 (1/4 for quafe) than the other then TC comes into play to assist in increasing the load on the side thats lacking.

Another thing about TC. There only has to be a big enough differance in wheel speeds for it to work. It doesn't require one wheel to stop before it will brake the spinning wheel. I'm going a little off topic here but the system the VW group uses considers all 4 wheel speeds and steering angle independanty. So if you were steering at full lock it would consider the inside wheel to be spinning considerably slower than the outside wheel. Unlike conventional older systems that would wait until the inside wheel had passed the speed of the outside wheel considerably before engaging, the VW system knows the wheel should be going slower than the outside wheel and will engage much sooner, even before the inner and outer wheel speeds have become the same.

One of the best things I like about TC and ATB is the abilitly to maintain full steering and that means I can articulate the very best line and a better line means I'm less likely to need the TC or ATB.

I think this debate can go back and fowarth thousands of time and it's going to come down to personal preferance.

Personally I think lockers have there place but for me it's in vehicles that operate by spinnng all 4 wheels through deep bog holes.

Happy Days

[Tusker]

Up until recently, I've always said double lockers used properly are superior in every situation to TC/ATB.

The steering lock argument is just wrong. If you're applying power on full lock, don't expect me to help with your broken CV.

This is compounded with off camber tracks - which all gnarly tracks are. TC/ATB needs wheel spin etc. You'll be sliding. A locked vehicle can apply power more gently.

What changed my mind? Where D3s & D4s go is just not fair!

Regards
Max P

[chook73]

I agree with you "Chook 73" that TC is reactive and lockers are proactive. I think I said it in an earlier post that it's a down side in mud as by the time TC works then traction is lost and it's too late but ATB fixes this.

I think you are wrong in the way you are thinking a wheel has to be spinning or operating at a different speed to the opposite wheel for the ATB to be working. ATB will work on load not rotational speed so if one wheel is in mud and the other on bitumen then most of the torque will be sent to the wheel on the bitumen and the wheel in the mud wont spin providing it has enough traction to hold 1/3 of the torque being sent to the other wheel.

ATB diffs are proactive until a wheel gets less load than 1/3 (1/4 for quafe) than the other then TC comes into play to assist in increasing the load on the side thats lacking.

Another thing about TC. There only has to be a big enough differance in wheel speeds for it to work. It doesn't require one wheel to stop before it will brake the spinning wheel. I'm going a little off topic here but the system the VW group uses considers all 4 wheel speeds and steering angle independanty. So if you were steering at full lock it would consider the inside wheel to be spinning considerably slower than the outside wheel. Unlike conventional older systems that would wait until the inside wheel had passed the speed of the outside wheel considerably before engaging, the VW system knows the wheel should be going slower than the outside wheel and will engage much sooner, even before the inner and outer wheel speeds have become the same.

One of the best things I like about TC and ATB is the abilitly to maintain full steering and that means I can articulate the very best line and a better line means I'm less likely to need the TC or ATB.

I think this debate can go back and fowarth thousands of time and it's going to come down to personal preferance.

Personally I think lockers have there place but for me it's in vehicles that operate by spinnng all 4 wheels through deep bog holes.

Happy Days

Note that this thread is on the Defender forum so I was of the impression we are discussing defender TC not Disco, 200 series, VW TC as that is not relevant to Defenders.

A quote below from Dave Ashcroft (off his website), the guy that makes ATB's, note in particular the part On low or no traction surfaces where one wheel has considerably less traction than the other and thus tends to spin

"The ATB gear type limited slip relies on the internal friction generated by gear sets within the diff centre, these gear sets are unsupported and designed to be ineffecient. In a normal situation, i.e. on road this diff will be totally transparent, you will not know it is fitted. Provided both wheels have grip no torque biasing takes place, on a bend or corner the faster outer wheel will try to bind up the internal gears but the inner slower wheel constantly unwinds the gears, so again on a corner no bias is felt. On low or no traction surfaces where one wheel has considerably less traction than the other and thus tends to spin, the gear action within the diff causes friction which in turn applies load to the wheel with traction. The amount of torque applied depends on what is termed the 'Bias ratio'. Bias ratios can be varied by different pre-loads and different gear profiles but the most common have a bias ratio of approx 2:1."

Fact: ATB's are not pro-active, they are completely passive (i.e. dont work), for activation they rely on a wheel to loose traction before they come into play.

Fact: TC is not pro-active, they rely on a wheel to loose traction before they come into play. This is especially so on Defenders.

The argument that ATB/TC gives you better steering and therefore you can pick a better line and therefore you need less ATB/TC..... huh?

Your bizarre concept that lockers only have their place in vehicles that operate by spinning all 4 wheels through deep bog holes shows you have no concept what lockers are or how lockers operate. You need to stop watching 4WDAction DVD's my friend.

For most normal people lockers are about about making a more complete and capable vehicle that allows strengthening of driveline components and gives greater mechanical and environmental sympathy.

Your correct its about personal preference, thats the one thing you and I agree on but there is no way that you can argue that ATB's and TC will perform better than lockers.

[Sirocco]

We have been very happy with Truetracs front and rear in our 90. For a heavy vehicle towing, travelling/touring I don't think you can beat it for function, reliability, fit and forget. Sure its a compromise in the traction stakes, but I didn't want to be worrying about breaking half shafts, air lines and extra stuff 1000's of KM from a spare part.

Truetrac, fit and forget ;)

G

Sirocco Overland | (http://www.siroccoverland.com)

[Drover]

Note that this thread is on the Defender forum so I was of the impression we are discussing defender TC not Disco, 200 series, VW TC as that is not relevant to Defenders.

A quote below from Dave Ashcroft (off his website), the guy that makes ATB's, note in particular the part On low or no traction surfaces where one wheel has considerably less traction than the other and thus tends to spin

"The ATB gear type limited slip relies on the internal friction generated by gear sets within the diff centre, these gear sets are unsupported and designed to be ineffecient. In a normal situation, i.e. on road this diff will be totally transparent, you will not know it is fitted. Provided both wheels have grip no torque biasing takes place, on a bend or corner the faster outer wheel will try to bind up the internal gears but the inner slower wheel constantly unwinds the gears, so again on a corner no bias is felt. On low or no traction surfaces where one wheel has considerably less traction than the other and thus tends to spin, the gear action within the diff causes friction which in turn applies load to the wheel with traction. The amount of torque applied depends on what is termed the 'Bias ratio'. Bias ratios can be varied by different pre-loads and different gear profiles but the most common have a bias ratio of approx 2:1."

Fact: ATB's do not work on load, they work on rotational speed. That is how the ATB engages, one wheel spins quicker than the other and the force engages the gears. For the sake of this argument a wheel spins quicker either because it looses traction or because it is cornering.

Fact: ATB's are not pro-active, they are completely passive (i.e. dont work), for activation they rely on a wheel to loose traction before they come into play.

Fact: TC is not pro-active, they rely on a wheel to loose traction before they come into play. This is especially so on Defenders.

The argument that ATB/TC gives you better steering and therefore you can pick a better line and therefore you need less ATB/TC..... huh?

Your bizarre concept that lockers only have their place in vehicles that operate by spinning all 4 wheels through deep bog holes shows you have no concept what lockers are or how lockers operate. You need to stop watching 4WDAction DVD's my friend.

For most normal people lockers are about about making a more complete and capable vehicle that allows strengthening of driveline components and gives greater mechanical and environmental sympathy.

Your correct its about personal preference, thats the one thing you and I agree on but there is no way that you can argue that ATB's and TC will perform better than lockers.

Haha.....what Chook said X 2

[workingonit]

I get the impression load rather than rotational speed is important. The Ashcroft article goes on to say -

The disadvantage of ATB is that if one wheel is totally off the ground ,i.e. no drive then the other wheel similarly because the bias ratio is still 2:1 i.e. 2 x nothing is still nothing. Attempts at changing the preload or left foot braking can then fool the ATB into working or better still if the vehicle is fitted with ATC (automatic traction control) the ATB will enhance the action.

The video clip of the ATB still left me wondering about the physics involved.

[chook73]

I get the impression load rather than rotational speed is important. The Ashcroft article goes on to say -

The disadvantage of ATB is that if one wheel is totally off the ground ,i.e. no drive then the other wheel similarly because the bias ratio is still 2:1 i.e. 2 x nothing is still nothing. Attempts at changing the preload or left foot braking can then fool the ATB into working or better still if the vehicle is fitted with ATC (automatic traction control) the ATB will enhance the action.

The video clip of the ATB still left me wondering about the physics involved.

I stand corrected on that point.

[Disco Muppet]

Chook, have a read of this....

DEFENDER2.NET - View topic - ATB (torsen) front and rear install (http://www.defender2.net/forum/topic13545.html)

In particular...




To get the mostly found misunderstandings out of the way:
- a Detroit locker is not a torsen diff , it is an un-locker
- torsen, which is a LSD as it is not a full locker, has nothing in common with the classic friction plate based LSD’s which operate rotation speed based

I tend to categorize them in corrective and preventive aids.
Friction plate LSD and TC are corrective aids; they react once traction is lost
Full lockers are both preventive and corrective, depending on when you switch them on. But they are a passive system as they need to be switched on.
ATB’s are preventive, they transfer torque before and during loss of traction.

The main catch between both is that the first 2 are taking power, by slip or braking; so they work against the power you put into it, to regain traction.
The ATB’s do not. They transfer the power without consuming or braking it.

[chook73]

Chook, have a read of this....

DEFENDER2.NET - View topic - ATB (torsen) front and rear install (http://www.defender2.net/forum/topic13545.html)

In particular...

Clearly Dave Ashcroft is wrong then.....

[Sitec]

I think simply put, a Torsten diff works because its using worm gears, not open gears.. With a little load, these gears are pushed outwards causing drag hence pushing a percentage of the drive to the wheel that's still on the ground. Traction control or left foot braking helps this, but I also found that on my off road vehicle throttle bursts used to have enough effect to get the stationary wheel spinning. With a Detroit in the rear, there's usually a certain amount of forward motion... Add to that a percentage of drive from the front wheel that's still on the ground, gives enough to keep going!! :)

[PAT303]

Up until recently, I've always said double lockers used properly are superior in every situation to TC/ATB.

The steering lock argument is just wrong. If you're applying power on full lock, don't expect me to help with your broken CV.

This is compounded with off camber tracks - which all gnarly tracks are. TC/ATB needs wheel spin etc. You'll be sliding. A locked vehicle can apply power more gently.

What changed my mind? Where D3s & D4s go is just not fair!

Regards
Max P

It's all down to the indy suspension IMHO,watch a D3/4 L322 RR etc walk over ground with nice supple suspension movements,then watch a defender bounce over the same ground with the T/C clattering it's head off. Pat