Thread: Diff locks and traction control

I haven't watched all these, but hopefully you can get something out of it.

fitting an ashcroft atb diff youtube - Bing video

Originally Posted by Vern

If you can leave the pinion alone that would be easiest as you only have to set the backlash. But if you need to do the pinion bearings then you will need to set the pinion height which is much more involved.

The Utube Ashcroft video that bob10 linked to shows it. I need to watch it a few times. He uses a vernier height gauge that spans across the side bearing mounts. I am looking to buy one but the ones I have seen look different. He uses a block to zero it but I need to find out more.

Keith

Originally Posted by 123rover50

The Utube Ashcroft video that bob10 linked to shows it. I need to watch it a few times. He uses a vernier height gauge that spans across the side bearing mounts. I am looking to buy one but the ones I have seen look different. He uses a block to zero it but I need to find out more.

Keith

Yeah i use one too when i do my diffs

What does yours look like?
Any chance of a description?

Keith

Originally Posted by Vern

Yeah i use one too when i do my diffs

Would this do it OK?

Precision Digital Height Gauge 0 - 200mm / 8" | eBay

Something like this would do, but I'd go for a better quality one.

Sorry, broken link.

Originally Posted by tact

Gotta disagree here on two fundamental points.
1. I disagree with "...the ATB does in effect LOCK."

Quite the contrary - An ATB never "locks" fully. At best you can get maybe a 70/30 torque split. The only way to get full drive to one half shaft is to lock up the other halfshaft, stop it from rotating at all. (which would work on any diff - its not because the ATB "locked").

2. I disagree with "... until you require a locker it is an open diff"

The ATB will resist differentiation (but not lock) in proportion to the amount of load on the driveline
- regardless whether travelling in a straight line or turning,
- regardless whether on tarmac or ice.
- it is the amount of load, or "weight", or torque applied, onto the driveline that determines how hard, or how easy, it will be for the half shafts to rotate at different rates.
- and this resistance to differentiation, proportional to load on driveline, exists before its even needed/used. Before any differentiation action is even initiated. (by turning, or wheel slippage)

examples:
- If you are hard on the throttle on tarmac, even travelling in a straight line, the "weight" (applied torque) on the driveline overall is already causing the ATB to bind up (not lock fully) and make it hard for either half shaft to rotate slower or faster than the other.
- if you are on a light throttle, or coasting, such that there is little or no weight on the driveline then ATB effect is less but still present.

You mentioned climbing any hill you tackle easily with ATB's. I pretty much echo that. Whilst ever all wheels are on the trail, the hill climb puts a lot of weight on the driveline as you drive up. Thus lots of "resistance to differentiation" is already in play before any wheel even thinks about slipping. Almost like a locker, but its not "locked".

That makes a lot of sense. I was working on the theory a worm can drive a gear but a gear can't drive a worm and applied that theory incorrectly. When one wheel slips it is not essentially trying to make the gear drive the worm therefore lock.
I can very much relate to your last statement about hill climbing and torque biasing, there is much less stress on my car with the ATB fitted. The only scenario i'd require a locker is very low speed competition rock crawling type 4WDing which is not required from the vast majority of 4WD tracks in Australia. I guess it could be argued that lockers might put less stress on your car, but from my experience they are no longer the necessity they once were now many 4WD's come with traction control, fitting the ATB with TC solves most traction issues on tracks, but TC on its own isn't quite enough.

At the risk of repeating myself,





Hover over image to zoom




Product Information

We are pleased to announce the addition to our range of Diff Centres.

The Ashcroft Automatic Torque Biasing Limited Slip Differential

The key features are: -

• Fully automatic, needs no driver input
• Totally transparent on road, i.e, no unwanted adverse effects
• Only comes into play when one wheel looses traction, i.e, a difference in wheel speed
• Enhances the traction control as it multiplies the bias load created by the braking effect of the traction control
• Needs no special oils
• Needs no adjustment as the gears compensate for any wear that takes place
• Only with 24 spline side gears

The ATB, our latest addition, is a 'Helical Gear' type LSD with six gear pockets.
There are a number of other LSD available including the 'plate type' and the Torsen T1, we believe the ATB is superior to the Plate type LSD principally because of the high preload necessary to make the plate type effective, this high pre load leads to 'harshness and vibration effects' and causes high premature wear. The Torsen T1 was the forerunner ATB and relied on a different principle to generate cross torque, effectively using coupled worm and wheel gears, being driven backwards, to create the necessary friction loads. These often failed due to this high loading destroying the worm gears.
The helical gear type ATB has many advantages that overcome the objections to other designs. There is a minimal pre-load necessary to engage the gears but this does not cause excessive wear or harshness, the helical gear type is virtually invisible to the driver on normal road use as the gear/pocket friction simply does not occur.
So how does this 'helical gear' ATB work, as stated earlier there are six sets of helical gears, mounted parallel to the axle, each side 'sun' gear drives six helical gears, these mesh with six corresponding helical gears which in turn drive the opposite side 'sun' gear. The important factor is the fact that these helical gears are mounted in 'pockets' in the center carrier, so any radial load on the helical gears causes them the press against the side of the pocket creating friction. This is why we use six pockets as opposed to three in another well known brand, more pockets more friction and better ATB effect.
One of the drawbacks of the ATB is that it is always necessary to have some load on one wheel per axle. if there a no load situation eg cross axle the wheel with traction would only see approx three times the load on the wheel with no traction ie nothing!!. To overcome this, as stated earlier, the ATB is fitted with some preload springs to provide some loading to the side with no traction in the event of a cross axle, where this pre-load is not providing sufficient traction to the other side then one favourite trick is to apply a small amount of left foot brake whilst applying more throttle. This manouver fools the diff by providing load to the non-traction side which is multiplied by the ATB (approx 3:1) to the other side, the loss of drive attributed to the brakes which are acting equally on both wheels is overcome by the additional throttle. In a car fitted with Automatic Traction Control this braking all takes effect automatically and the ATB provides additional traction by multiplying the ATC effect.
The ATB diff can be fitted in the front or the rear, in the rear you will not notice its there during normal road driving, in the front it will make the steering self centre a little more than normal when coming out of a corner but this is only very slight and will lessen within the first few hundred miles and also you will find you automatically adjust to this feeling very quickly.
So why use an ATB instead of a locker?? basically when driving on a low traction surface. for example sand, snow, or even wet grass rather than have a locked diff which can 'cause' loss of traction for example when cornering as both wheel are forced to travel at the same speed, one wheel typically breaks traction allowing all the drive to the other wheel which will also break traction. the ATB will allow wheel speed difference but at the same time will always try to equalise the torque to each wheel, this reduces the possibility of a spin out situation.
Note : Due to the nature of the ATB diff we do not recommend the vehicle is brake tested on rollers, ask for a decelerometer to be used instead.