Thread: ATB Diffs

Originally Posted by komaterpillar

Selectable, as in i can turn it off or on as i feel necessary, and it goes back to a plain old open centre for the drive home. And i figured for the $70 price difference i may aswell just go all the way to a selectable locker.

Another reason was, I've had a few hairy situations on wet bitumen in my defender, mainly from me having 33 inch muddies on and going to fast for the conditions. But I didn't want anything that could provoke that situation anymore.

Fair comment there. I had an Aussie lokka years ago (auto locker, really "auto un-locker" would be a better term). On a wet road, rear wheel drive, while cornering only the inside rear is actually driving the vehicle forward. (The outside rear would be basically freewheeling and overrunning the "unlocker" centre). It's not too hard to put down enough throttle to spin that inside rear wheel on the wet road. Then the locking action kicks in and steering gets interesting.

Originally Posted by tact

Fair comment there. I had an Aussie lokka years ago (auto locker, really "auto un-locker" would be a better term). On a wet road, rear wheel drive, while cornering only the inside rear is actually driving the vehicle forward. (The outside rear would be basically freewheeling and overrunning the "unlocker" centre). It's not too hard to put down enough throttle to spin that inside rear wheel on the wet road. Then the locking action kicks in and steering gets interesting.

I had the Autolockers (or Unlockers) on my little Suzuki Vitara LWB that was my daily driver. In general it fairly normal on road but getting into my work car park became a PITA with the tight cornering I had to do. I had the Autolocker in the Zook for a couple of years I think, but the added stress on the Rear Axles took its toll with me eventually breaking a rear axle far from home. After that incident, I removed it from the rear, left the one in the front as I had FWH's and replaced the rear with a Chinese ARB Knock off worked fine for the time I had it for..... Until it started leaking air
So for me, I would not be bothered with an Autolocker again but the ATB might suit my driving needs but looking at the price difference between the Ashcroft and the ARB lockers, I could be talked into going the Ashcroft lockers.... if I had the $$

Originally Posted by tact

To get an ATB equipped vehicle to be half as good as a locker, when staring up a steep rutted climb with a wheel or two hanging in air
[...]

(Quoting myself - ultimate arrogance?!)

Lets not forget going DOWN that hill. Here again full lockers are the ducks nuts. I prefer a feet off approach to steep (slippery or not) descents.

With open diffs or ATBs (which, as good as they are elsewhere, when a wheel lifts they magically behave as if open diffs) - as soon as a wheel lifts on said steep slope you lose the engine compression braking and control on the wheel at the other side of the diff too!

Not so with full locker if engaged before the descent.

Ok I had a leaking rear pinion seal for a long time. As photo shows brand new synthetic diff oil isn't a match for many deep creek crossing at the top end...and 3 good solid peas worth of metal (on top of the 3 good ones I removed 6000k ago immediately before the Cape Trip...

So. My rumble on deceleration that I have noticed lately and have put down to a diff is probably rear diff wear.

I am considering an ATB. In a cross axle situation how much quicker is drive transferred in a D2 (CDL Locked) to the opposing wheel with an ATB versus open diff with traction control?

Cheers

Originally Posted by djam1

Interesting d

My car - D1 with 2 Trutracs. No ETC.
Based on this video I should get very significant and noticable drive to the grounded wheel by braking when the opposite wheel lifts.
Does this video show normal Trutrac operation?
I replicated this recently on my front axle (one wheel up and one grounded) and it didn't apply any significant drive to the grounded wheel... wouldnt even pull the car forward while up on the trolley jack.
What is wrong with my TT?
The reason I tested it was after a trip with my car and a friends 70 series toje - mine was no better on the cross axeling sections than his which is standard trim ie just rear LSD no TC.

thoughts?

Edit: I have just watched this Watch before you buy Eaton Detroit TrueTrac differential! How do they work? - YouTube

It maybe that I am not being firm/aggressive enough with the braking. I will re test with the trolly jack and report back.

Edit 2: Ok my TT's are fine. The problem with the last time I tested them using a trolley jack was that I was in high range. In H there is not enough torque to trigger the torque transfer to any significant level.
In L I can easily drive off the jack and if I wanted to I could probably replicate the first video. I further tested it by properly cross axeling the car in the back paddock..then driving out easily with fairly firm use of brake pedal then driving 'through' the brake resistance.

With regard to my friends Toje and how well he goes in comparison... well he is an excellent driver, and he had 33's (vs my 31's) and a longer wheelbase..and I wasnt using my TT's optimally ( obviously :-))

In summary - twin TT's are excellent - but no where near as good as locking diffs for the real rocky rough stuff.

If there is no torque on the lifted wheel there is no torque transfer.
There has to be resistance on the spinning wheel for the torque to be transferred to the other wheel.
Thus the advice good on snow or one wheel in mud etc. Nothing is said about wheel in the air.
So wrong test.
However with TC the braking of teh spinning wheel will provide torque to be transferred to the wheel on the ground. (as will a normal diff but more torque with truetrack depending on the bias ratio)
Regards PhilipA