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Ashcroft ATB

£335.00

5.0 average, based on 10 reviews

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.

Please click here to see an interesting thread about these on the Defender 2 forum,


Please click  here to see a video of the Truetrac which is very similar in operation,

 

The ATB can be supplied alone or assembled in to a diff centre. Please see here for a price on a complete assembly,

If you want to fit one of these ATB's into a late (2002 onwards) 110 rear diff you will need one of these.

Note this is not for the Salisbury axle, if you want an ATB for the Salisbury please see the Detroit Truetrac.

They are made to fit metric bearings and a metric diff casing, we are able to supply a pair of these new journal bearings (RTC3095) at £ 20 / pair and we would be happy to fit them if you would like, please see the drop down tab above when ordering.

Fitting Options

If you bring or send us your diff we are able to install the ATB centre for £95 per diff assuming the diff is in good running order.   If the fitting is to a P38 diff then there will be an additional £32 for the P38 Spacer Ring required to fit.

In some incidences there may be additional parts required and these will be charged in addition to the costs above.

If you would like to bring your Defender to one of our fitting stations and have the diff removed from the vehicle, the ATB fitted, as above we are able to do this. Costs for this are £175 for the front diff and £150 for the rear.  Note these fitting charges are in addition to the costs to fit the ATB centre to the diff itself.

Note these costs assume you already have a 24 spline axle.  If you are upgrading from a 10 to 24 spline set up you will require additional parts and these prices will be incorrect.  Please contact us for further details if you are looking to upgrade the axle.

We can do one diff in one day but if both front and rear are required then we may require your vehicle for up to two days.  A courtesy car is available, free of charge, whilst the work is being done.

All the above prices exclude VAT.

 

See video below of a happy customer using his new ATB's in a desert in Dubai:

 

 

 

 

 

SHIPPING COSTS

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Product Code: ASHATB

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Customer Reviews

[1] 2 > View All Average Rating: 5

Rear Ashcroft ATB in my serie 2a

In januari I ordered a pegged diff with Ashcroft ATB and a set of HD serie drive shafts to beef up the weak rear axle of my serie 2a 88 pickup. When it arrived I was surprised and delighted to find that it was fitted with the HD ring and pinion which I had not specified when ordering. Great service. First testdrive was in the snow and that immediately put a big smile on my face. So much better then an open diff. Since then I have done a couple of weekends offroading and the smile only got bigger. Deep muddy ruts or cross-axles that would normally stop the 88 are no problem any more. The added strength of HD parts and pegging also gives me the confidence that I can put my foot down when I need to which I Always was reluctant to do with the Original serie 2a diff and half shafts. Next job on the list is to beef up the front axle. So dave, if you can find the time could you develop some HD 24/24 spline serie front half shafts? ;)

Eric Tol :: Apr 02 2016, 08:00 AM

rear ATB

Have one in my rear axle on 110 Tdci. Very pleased how it works. I don't have ABS, so i have to press brake sometimes to make it work. But it does the job! Front is next on the list.

Bostjan :: Dec 11 2015, 15:40 PM

ATB diff

I am very pleased with this diff. It works great. I also have the TC on my DEFENDER 110 Td5, and with this ATB, the vehicle is unstoppable. I drive many times on wet grass with the heavy trailer after the hunt. No problem any more. I do recommend. Also the Ashcroft company, no problem to deal with. Thanks a lot. Mirko from Slovenia

Mirko Merzel :: Nov 17 2015, 14:35 PM

very good

I have one in the front and one in the rear off my classic tried it in a wet clay bank went up no problems no traction lights comeing on before i had these in it would have been spinning the wheels with traction light on well impressed

michael sillitoe :: Nov 09 2015, 22:17 PM

Well worth it

These are good value units at a very competitive price. Mine arrived promptly, well packed and ready to fit. I added new bearings to my diffs and whilst the axles were apart I renewed the wheel bearings and steering swivel bearings at the same time, as well as all the seals I could reach. Driving impressions are good. The vehicle feels steadier at motorway speeds and I now have to keep a careful eye on the speedo, rather than suffering from a jittery feeling at 70 or so to let me know I was past the legal limit, as before. Wet, winding A roads are not so much of a white knuckle experience either. However the real improvements come on wet and slippery surfaces. Where there's a layer of liquid mud and manure, where the sun has melted a thin film of water on the surface of frost, or where there are steep slopes with wet grass, the vehicle is much more sure-footed and it is far harder to spin a wheel. With no traction control or ABS, my Defender now outpaces the one belonging to a friend which has electronic traction control on slippery slopes. On my many visits to Wales last winter I found I could drive effortlessly up slopes that were too slippery to walk up. Just use the highest gear possible so as to keep the torque at the wheels down to a sensible level, and it will climb and climb. Next time I have a few hundred pounds to spare I'll get the limited slip centre diff as well.

Brown :: Oct 29 2015, 22:14 PM

[1] 2 > View All Write a review

 

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