Thread: TC plus centre diff lock - when?

Originally Posted by cuppabillytea

Yes well.and here was I thinking all that stuff was standard. That's good mod to put in. I don't think the ABS is a huge loss though. You get used to it and drop a skill level.
Cheers, Billy.

To be honest I am not a big fan of electronic traction control (ETC), it must hammer the brakes and is rather complicated stuff with all the sensors etc. But I reckoned that with the decision to not fit a winch I'd likely need a little bit of help now and then - and ETC could deliver that. Reviews seemed to say that the newest versions of ETC were getting pretty good.

In many ways I am very happy to have been denied ETC by the Malaysian importer - I really like how the Ashcroft ATBs work. And they do work vey well!
- no electronics needed
- no sensors to damage or fail
- no friction pads/parts to wear out (i.e. brake pads with ETC, no clutch packs as in LSDs)
- seems to be more proactive than the definitely post-active nature of ETC.

The last point is liable to misunderstanding and controversy so will elaborate a little here:
The best way that I have come across to understand how ATBs (torque biassing diffs) work is like this - they are open diffs that are very bad at being open diffs, poor at allowing half shafts to rotate at different speeds.

There is one exception to the above statement, ATBs are good at being an open diff ....when there is no torque being applied to the diff input(s).

Notes:
1. "good at being an open diff" is a bad thing sometimes, its what you invest in these things to avoid!
2. diff "inputs" (why plural?): driving forward/reverse has the pinion as input, driven by the engine. Turn that around, when under engine braking, the half shafts are the inputs. ATBs work equally well (at being poor open diffs) either way.

When is there ever a "no torque" situation, which would cause the ATB to do a pretty good imitation of an open diff?
1. When you are coasting. i.e. in neutral, or clutch pedal down, broken drive components, and be aware.... when in gear but throttle position such that you are neither applying drive to the wheels, nor the wheels driving the engine.

2. whenever a single driven wheel on one side completely loses traction (e.g. wheel in air)

Note: this is because torque needs something to push against (overcome) or it doesn't exist. (Very layman's explanation)

So with an ATB: whenever you are applying drive it binds up and resists half shafts turning at different speeds (whether they are trying to do so or not). The more drive force applied (torque), the more resistance to differentiation.

So when one of those driven wheels encounters a patch of ground slippery ground - the diff is already resisting any differentiation action. Then when shafts do start turning at different speeds the ATB, being so bad at being open, still drives the non slipping wheel. (pre-active)

Whereas with ETC, the wheel on the slippery stuff has to break traction and spin up faster than the other wheel before the brakes are applied to control it. (post-active)

Ive got an ATB in the front diff and its great on-road and provides added traction offroad until you lift a wheel. Then it's inferior to a locked diff or traction control. One of my favourite mods to be honest. Made a big enough difference in 99 percent of driving to be forgiven for the 1 percent. Would be perfect with TC. Works really well with a locked rear diff and is nice to CVs compared to a locker.

Traction control has been good enough for me most of the time. There have been a few situations but not irretrievable, where more traction would have meant, no problem.
I don't like TC on rear wheel drive road cars but I like the way it works on the Defender, and although I live in fear of Murphy's Law the complexity of doesn't worry me too much.
If I keep ending up in places I didn't mean to go, which I probably will, then I will eventually fit air lockers front and back.
Given your situation Neil, I think you've done as well as you can.

Originally Posted by steane

Ive got an ATB in the front diff and its great on-road and provides added traction offroad until you lift a wheel. Then it's inferior to a locked diff or traction control. One of my favourite mods to be honest. Made a big enough difference in 99 percent of driving to be forgiven for the 1 percent. Would be perfect with TC. Works really well with a locked rear diff and is nice to CVs compared to a locker.

Absolutely 100% well said and supported.

Just to add... Left foot braking does actually help when there is an ATB involved. Definitely left foot braking won't be as good as ETC or a fully lockable diff, at getting torque to the wheel that's not in the air. But left foot braking is actually of some help when an ATB is fitted.

Heres why:
Left foot braking puts the same braking effect on both wheels. Both sides of the diff. Regardless one wheel in the air and one has traction.
- If the diff is an open diff it doesn't help a lot.
- If the diff is an ATB, while the braking effect is similar, the ATB will bias a bit more torque to whichever wheel is turning slower. Even just a little braking on the free spinning wheel will result in a bit of extra oomph heading to the other wheel.

Anyone experienced Tc with Ashcroft Lsd?

Originally Posted by AndyG

Anyone experienced Tc with Ashcroft Lsd?

Not me personally, of course, but in my reading have seen comments that indicate the traction control indicator hardly ever lights up after fitting ATBs

Certainly when a wheel is in the air the ETC would kick in on just that wheel and be way better than left foot braking, with ATBs, at getting torque to the other wheel.

As already mentioned and well covered...

I "teach" customers to:
On gravel, do whatever takes your fancy, on anything beyond that ENGAGE the centre diff.

The traction control on any Land Rover that has a LT230 transfer case (Discovery 2, Defender TD5 onwards) wont react quick enough to stop the side gears from spining and wearing out the side shims.

I call this wear on the side shims "Discovery 2 wear" as there was that year model that had no option to lock the centre diff. The bronze shims on the side gears wears so thin they either disappear completely or if still there are so thin they can be riped like paper.

Regards
Daz

Used both TC and a locked centre diff up a steep, rutted, slippery forest trail at Possum Brush near Taree last week and it went very well. While the son in his lifted Hilux (no lockers or TC) with fat Cooper STs was spinning wheels and sliding about, George just ambled up in low-second (first was too slow) on his original GG TRs with minimal fuss. Very happy chappy I was - made my driving look better than it actually was.
I can see the potential benefits of an ATB, but at the moment there are higher priorities for my $, so its down my wish list.