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Ashcroft Torque Biasing Diff Centre


5.0 average, based on 18 reviews

Product Information

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


The Ashcroft 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 adjustment as the gears compensate for any wear that takes place
  • Only with 24 spline side gears

The Ashcroft Torque Biasing centre works best with a good quality Mineral based oil, we do not recommend synthetic oils, friction additives / modifiers and not required.

The Ashcroft Torque Biasing centre 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 Ashcroft Torque Biasing centre 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 Automatic Torque Biasing centre 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 Ashcroft Torque Biasing centre 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'  Torque Biasing centre 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 Torque Biasing effect.

One of the drawbacks of the Torque Biasing centre 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 Torque Biasing centre 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 Automatic Torque Biasing centre (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 Torque Biasing centre provides additional traction by multiplying the ATC effect.

The Ashcroft Torque Biasing centre 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 Ashcroft Torque Biasing centrenstead 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 Automatic Torque Biasing centre 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 Ashcroft Torque Biasing centre 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 Ashcroft Torque Biasing centre  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 Ashcroft Torque Biasing centre 's into a late (2002 onwards) 110 rear diff you will need one you will need to select the P38/Wolf type.

Note this is not for the Salisbury axle, if you want an Ashcroft Torque Biasing centre  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.


Diff Pegging   This is an option for those customers who are fitting their  Ashcroft Torque Biasing centre to a pegged diff.  It is not an adviseable option if the Torque Biasing centre is being fitted to a standard diff.   If you are pegging the diff the outside diameter must be reduced to clear the pegging pad.  If you do this op and then fit to a standard, non pegged diff, the Ashcroft Torque Biasing centre will be weaker .  For more information on pegged diffs please see here


Fitting Options

If you bring or send us your diff we are able to install the Ashcroft Torque Biasing centre for £95 per diff assuming the diff is in good running order.  

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

All the above prices exclude VAT.


See video below of a happy customer using his Ashcroft Torque Biasing centre 's in a desert in Dubai:







In order to calculate your shipping costs you will need to put the items in your shopping basket and confirm your delivery address. Once you have entered these details a shipping quote will be generated. Please do not proceed to the payment stage unless you are ready to order.

Product Code: ASHTorqBias

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Customer Reviews

[1] 2 3 >4 View All Average Rating: 5


As I do mostly beach driving I didn't want the hassle of a locker diff and the more I read about the ATB's on road manners the more impressed I became. now that they are fitted I'm even more impressed , works well with traction control even in bad situations , it just powers on through my only regret is that with a ST2 remap I'm now spinning the front tyre's so I've ordered the center one now - should have done this in the first place :)

Andrew Prior :: Jul 28 2021, 13:31 PM

Awesome engineering

Having fitted this diff into my front axle during a major restoration, viewable on my YouTube channel "Defender90 Keswick", I can assure everyone that this is a beautifully engineered product. the fit and finish is astounding.

Nigel Frampton :: Apr 20 2021, 20:54 PM

ATB = Astonishing Terrain Behaviour

Had one of these fitted along with HD CW&P and matching HD halfshafts to our beloved Series 3 by Nige at Excees4x4. The build quality is apparent and the finish is first class. I can now drive the old 88 up mucky slopes in 2WD which used to have it scrabbling about in 4WD. Well worth the money and can't wait to save up to do the front axle. Folks - this IS the diff you have been waiting for!

Tom Wykes :: Jun 15 2020, 17:08 PM

Fast delivery nice service

Fast delivery to the Netherlands and after that very nice and quick answer on my questions. Just top.

Bert Both :: Jan 27 2020, 19:45 PM

Awesome Prduct

Build in was easy fits perfect. Drives very good. Great Product.

Stephan Ziem :: Nov 19 2019, 09:32 AM

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