Thread: Torque Biasing Diffs

Originally Posted by Sitec

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.

Originally Posted by Blknight.aus

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..

Originally Posted by joel0407

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.....

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....

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

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

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

Originally Posted by 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

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.

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

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