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Ashcroft Torque Biasing Diff Centre


5.0 average, based on 17 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 >4 [View All] Average Rating: 5

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

ATB diff

sorry 5 stars

robert watts :: May 03 2018, 20:38 PM

ATB diff

Recently fitted 2 ATB diffs to my otherwise standard 90 all I can say is they are almost imperceptible on the road other than less back lash, however on wet grass its now like driving on dry grass, no slip and slide just drives off. Cant wait to see how they perform on more challenging terrain

robert watts :: May 03 2018, 20:36 PM

ATB’s in sand

Just completed the Canning Stock Route and Gunbarrel Highway towing a 1.5 t camper. Ashcroft ATB’s front and rear, their performance in the dunes and soft sand was quite amazing. Never looked like getting stuck once, recovery gear stayed packed away for the entire trip. Great product! Paul.

Paul :: Oct 20 2017, 22:42 PM

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


I do quite a lot of 4wding and when my standard diff failed i decided to put an ATB in. These things are subtle. You cannot feel them in day to day driving and even when i hit the tracks they do their job seamlessly. I especially found driving in sand to be much easier. No where near as much momentum needed as i dont lose drive to 1 wheel. As soon as funds allow i will be ordering 1 of the front.

Russ Leggett :: Jul 12 2014, 09:14 AM

Front ATB & Ashcroft pegged ARB in rear

Hi Dave, I fitted one of your ATB diffs in the front axle of my 90 TD5 to complement the Ashcroft pegged ARB in the rear. For us this is an extremely impressive set up. We use the Defender for long range camping trips so on-road manners are important as well as off road traction. The front ATB has tightened up steering feel no end (2005 90 with 75,000 miles, AB/ETC) and fast dirt tracks are so much fun with an open rear diff. Travelling low mountain passes in the snow this year we found the ATB to be exceptional, where at times engaging the ear locked induced side slipping. i am so impressed that I will be ordering another ATB for my 2nd 90 as soon as you have more stock. Also, love the fact that I can "Buy British" again & not get second best. Well done.

kevb :: Jun 13 2014, 16:42 PM

ATB five stars

Just realized I forgot to give you 5 stars. It was a real pleasure to deal with your company, I would recommend you wholeheartedly. Cheers John

John White :: Apr 05 2014, 21:09 PM

Automatic torque biasing differential

Having got fed up with breaking diffs every time I did a play day, 3.9 V8, 35" Fedima sirrocco's and a heavy right foot, I asked Dave his advice. Was it to be 4 pin diffs or ATB's? Dave recommended ATB's and since fitting them to the front and rear I have had no more breakages plus much more grip. A pleasure to deal with this company.

John White :: Apr 02 2014, 20:07 PM

New ATB's

Hi , Dave Thanks for your recent supply of the 2 rebuilt differentials , and the prompt delivery , much appreciated , they arrived on friday , by saturday night I was rolling , My observations so far , I was a bit wary of having one fitted in the front but I have drove a few miles and am made up with how it handles it isnt realy noticeable and no bad affects , I do have a terrafirma steering damper on which I think helps to stop all associated steering snatching / wandering with land rovers , so all good , I did have one of your Atb s fitted in my lr 90 , in rear and realy liked it as you may remember me mentioning , When I bought the disco 2 , I noticed the tc wasnt working properly , and I did a few trials before I fitted your cdl lever , It was just a cart road driving onto a field quite a steep slope , and drove up and down at 45degrees , results as follows , no cdl engaged , truck came to a stop 1 wheel spun out , with cdl engaged truck went all the way up / with slight manual brake intervention , with both Atbs fitted and cdl engaged , truck drove straight up no messing or spinning , could of almost been pouring my brew out my flask whilst driving up ha ha , but also interesting today I drove my dads new discovery 4 , up the same slope , it did make it to the top but there was wheel spin and traction control obviously kicked in and did get up to the top , so I am happy with them in front and rear , also just to mention , / I did notice out of the 2 diffs one seemed to have a slight bit more backlash in one than the other , I pressumed this was normal or within the tolerances allowed so I wasnt worried , and opted to fit that 1 in the front for maybe a little more give to be allowed , however when fitted and with new propshafts on the degrees of free play in total seemed to be similar approx 20 / 30 degrees so I was happy , anyway thanks again hope I havent bored you too much with detail , feel free if you have any comments to reply When you get a minute . Regards David

Admin @ Ashcrofts :: Jan 15 2014, 09:29 AM

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