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Home > Technical > ATB (torsen) front and rear install

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Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 713

While the footage of that video is interesting, the text given is just a bit dumb and lack of understanding of how a diff works. Also note, with the TCS on the diff and vehicle did exactly what is was meant too, even in the fade to black bit at the end of "part 1" when it drives out of the cross axle. At the end of the day a limited slip differential is exactly that ---- limited slip. Not no slip. If you are expecting it 100% lock and turn both wheels on an axle at 100% the same rate, then that is just a mis understanding of what it is. There are different types of LSD, clutch plate, viscous and TorSen (aka ATB). As well as electronic ones, which we will ignore here as they aren't relevant. ATB's require some loading of both wheels to operate. It's in the name, automatic torque biasing. On something as slippery as snow and cross axled, it is more akin to having the wheel in the air. There is no loading at all. The TCS will apply load to the spinning wheel and make the diff function, as the video actually demonstrated. You can left foot brake to do this, but it takes some practice and is way less effective, as of course you are braking both wheels on the axle, not just the spinning one. I've found something kin to cadence braking works best but you really need to apply the brakes. I know in the video the brake lights came on, but the spinning wheel never even slowed, showing that no real loading or braking force being applied. It also explains why it then worked with the TCS on. Also transferring power to a stationary wheel with a static vehicle is far more difficult than one that is moving. The ATB is generally going to work best if you maintain at least some momentum. Ultimately a full locker can have advantages, it would have 'forced' both wheels to rotate together. But there are also heavy limitations too. You can't steer very well with a locker engaged. And for climbing a front locker would be way better than a rear one. Lockers also require additional installation be it air or solenoid activated. They also are a passive setting requiring the driver to know when to use them and when not too. They also offer no use on the road. i.e. in the snow you wouldn't be able to run on the road with a locker engaged safely. An ATB is a fully active solution and requires no intervention from the driver directly, it will work in all weathers and all conditions and offer benefits on road as well as off. Before e-diffs, an ATB would have been the choice for most rally cars and competition. An ATB will work better with a TCS system, but they should still offer decent gains over open diffs on any Land Rover, even without TCS. Another option you could look at is a Detroit Locker. Although it would be better named as an unlocker... These work the other way round to a limited slip diff. They are locked, but will automatically unlock to allow you to corner. Off road they should be very effective and again require no user interaction at all. I've not personally used these, but as I understand it, they tend to favour longer wheel base vehicles more so and can have some odd side effects for on road driving as well as being audible when the unlock and re-lock. I know a couple of people with the Ashcroft ATB's, they have been very happy with them. I'll try an upload some footage. Ultimately it really comes down to your intended use, understanding of how they work and realistic expectations. A different diff might type might well suit your needs/wants better.

18th Jul 2023 5:05pm

Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 713	Not the best footage ever, but might help give you an idea.
18th Jul 2023 5:13pm

LandymanStefan Member Since: 30 Aug 2017 Location: Surrey Posts: 881

Thanks for your detailed response. I just want to clarify I’m not criticising the atb’s, just digging for more info to see what would be the best route for me to go. Since you’ve mentioned it I agree you can see that the wheel on the disco in the video doesn’t change speed despite the brake lights coming on. I’m really interested to know if anyone here has had first hand experience of getting out of a cross axled style situation by using the braking technique to force the torque across the axle or if the idea isn’t that successful in reality. I can see a lot of the benefits of the dual atb setup, the automatic nature, the onroad benefits, the fact I could get one in the front and rear for the same price as just a single rear locker setup and the list continues. However for me if you can still get quite seriously stuck if you have a wheels lifting I wouldn’t want to be in a situation where I’ve spent the same as I could’ve on a rear locker not being able to tackle an obstacle that I believe I would’ve been able with a locker. I am still on a standard suspension height with anti roll bars so I haven’t got the greatest of flex however I’ve not had an issue with clearance and I don’t want to compromise the on road handling I have with bigger suspension to gain traction. I know there’s the arguments about how with the correct line choice etc etc you shouldn’t need a locker but you can’t always guarantee you’ll take the perfect line and as I intend to do more off roading with the trailer reversing down a narrow trail to pick a better line won’t always be an option. I don’t think the Detroit locker is right for me as I have read about the on road compromises, which I’m not willing to take. I’ve narrowed it down to either twin atb’s or a rear locker. Just interested in peoples experience with the atb’s and getting stuck or crossaxled (or not) as the case may be.

18th Jul 2023 9:13pm

MarkBrown Member Since: 03 Oct 2022 Location: Mid Wales Posts: 451

I can't help with the ATB as I've not got one, nor tried one. However I have owned a few Jeeps and have found the following: Jeep XJ Cherokee - standard friction plate rear LSD. Bear in mind that this was a 4l automatic and would function in 2wd or 4wd on tarmac. This system I found to be borderline dangerous, as when cornering the gearbox would have the tendancy to kick-down, often mid corner, which meant that the inside rear wheel would spin, the diff would then lock, which would cause the back to overtake the front, as both wheels were then locked. This I had removed. On my second XJ fitted with standard open diffs, I had a situation where on a side slope both the driver's side wheels were spinning, due to the angle of lean on the track. Some left foot braking, on and off, gave sufficient grip to the other two wheels to get going. So tapping the brakes does work to transfer power to the opposing wheels, even momentarily, without any diff locks. My third Jeep was a WK Grand Cherokee 3l auto, that thing was amazing. It was fitted with Electronic Locking Diffs, which were superb. All you needed to do was engage low box and keep the power on, the system would then lock the diffs after a given amount of wheel slip. Without that feature the car would be pretty useless on the rough stuff as it had no articulation. It really was very good, when it worked, or the abs wire wasn't ripped out. I then sold it to get back into Land Rovers, which I once said I'd never do, but that WK was just soulless. A Friend has a Lwb Toyota Land Cruiser, which is fitted with a factory rear locking diff and I've noticed how steadily he can approach obsticals with it engaged, when compared to my Land Rover 110, which would require a little more momentum to clear the same thing. From what I've learnt from those other systems, along with what I've read, I'd say that one switched rear locker or twin ( or triple ) ATB's would be comparable. I'll be fitting the ATB center diff, and have a spare Salisbury rear to fit one into, when funds allow. I think that they'd be ideal for typical green Laning, snow roads and muddy fields that we get in the UK.

18th Jul 2023 10:23pm

Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 713

The centre ATB would only really benefit rally style driving IMO. As you'd be able to get the back to step out easier (less understeer) and retain better steering than having the centre diff locked. I don't know how effective the centre ATB would be on technical terrain. I do wonder if it might work on a trials vehicle, as again you'd get better turning. But you'd still want and need to be able to send power to both axles. The viscous Borg Warner unit (from the RRC/p38a) is a common choice as it is a limited slip centre diff. But I don't know if an ATB would work as well in such a situation.

18th Jul 2023 10:44pm

LR90XS2011 Member Since: 05 Apr 2011 Location: bickenhill Posts: 3640

the ASHCROFT ATB fitted in the transfer box still allows the centre diff lock to work so win win, it is on my list of future upgrades. I already have them in both diffs, but have little off road experience and I have TC/ABS. On road they are loads better than open diffs, car is just more planted and the dynamics are better. On wet grass it has loads more grip. DEFENDER 90 TDCI XS, I hope everyone is well and your land rovers make you happy

19th Jul 2023 5:25am

jimbo55 Member Since: 15 Jul 2020 Location: Midlands Posts: 398	Admittedly I have Ashcroft air lockers in the diffs, but I am awaiting my atb transfer box, One point is often missed is the impact that the atb transfer box will have under braking, especially on non abs vehicles. The atb will help prevent the rear axle going light or even locking up under braking as the atb will start to lock when one goes light
19th Jul 2023 4:12pm

MarkBrown Member Since: 03 Oct 2022 Location: Mid Wales Posts: 451	No reason not to fit one then!
19th Jul 2023 5:55pm

LandymanStefan Member Since: 30 Aug 2017 Location: Surrey Posts: 881

Interestingly I’ve been doing a bit more digging and have found a post on another forum from Nigel of xcess4x4 saying that if you fit an atb to the front you really should be upgrading your front shafts and cv’s. One of the benefits I was looking at with a twin atb setup is that they would work out more cost effective than a single rear locker + shafts etc. Being able to purchase 2 built atb’s for the less cost than a built rear locker, shafts and flanges. Having to purchase front Ashcroft shafts and cv’s for a twin atb would be an additional £900-1000. Definitely a consideration. Are you chaps on here with both front and rear fitted running upgraded shafts and cv’s or are the standards holding up fine? Click image to enlarge

19th Jul 2023 9:12pm

LR90XS2011 Member Since: 05 Apr 2011 Location: bickenhill Posts: 3640	All other bits on my front axle are standard and original, but as stated mine is road use, I'm approx 30k in with no issues, I do tow a caravan and drive it spiritedly frequently (without the caravan), I also still have the original front drive flanges at 50k miles now with no perceivable wear. Mildly IRB tuned 2.4. DEFENDER 90 TDCI XS, I hope everyone is well and your land rovers make you happy
20th Jul 2023 5:27am

Lodelaner Member Since: 04 Feb 2010 Location: Lambourn Posts: 631

LandymanStefan wrote: I’m really interested to know if anyone here has had first hand experience of getting out of a cross axled style situation by using the braking technique to force the torque across the axle or if the idea isn’t that successful in reality. Through experience and not inconsiderable cost, I would say that if you want to benefit from an ATB, keep it transparent on road and get maximum cost benefit, just put one in the back and gently feather the brakes. I've tried a few combinations: - Rear ATB on a V8 90 Station wagon manual then on a 50th Anniversary Defender auto (they don't have TC) - Front and rear ATB, - Rear ATB only - ARB locker on the rear only The braking technique took a while to get the feel of in the V8 90, initially I was using too much brake and then learnt to feather the brake. All you need to do is give it a helping hand and provide a little resistance to prevent spinning so the tyre can find traction. The technique that worked for me was to just keep the power on and the back end would wiggle around - a bit like a Land Rover twerk - and then it would find the available traction and grip to progress. I liked it so much I had front and rear ATB fitted to the 50th. With the auto box it was easier to left foot brake and it was pretty effective. However on the short wheelbase I didn't like the effect of the front ATB on tarmac - power-on understeer and the way it tightened its line when lifting off. It wasn't dramatic, I just didn't like it in combination with an Overfinched V8. So I removed the front ATB and went with the rear ATB only. I ended up breaking the front diff though on a simple little rock-step that I was trying to climb up - I should have let the diff do its own thing. Instead I over-braked to find traction, not realising that I was cross-axled and a front wheel was spinning - and then I heard the horrible ratchet sound of gears as the front diff let go. I have a video somewhere - it still makes me shudder. I then put an ARB in the back. I only ever used it when I was stuck - never to get into a situation where I got stuck. It became known as the 'unstuck' button and it was brilliant. JB @Lodelaner Instagram Youtube greenlaning and other LR related content

20th Jul 2023 7:44am

geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410

Really interesting experience and observation JB You are quite right about the left foot braking being a feathering action rather than a stomping one. Back in my youth I was told about this miraculous left foot braking being able to transfer drive to wheels with traction and to put a long story short I had the right idea but the wrong methodology... Bang goes the CV Hey-ho. Having just fitted an ATB to the front of Miffy and shortly about to do the same with the rear it will be interesting to see how things feel and what things are in fact different as well. I am hoping that being a 110 and a lowly TD5 the understeer you mention will not be an issue

20th Jul 2023 1:59pm

Lodelaner Member Since: 04 Feb 2010 Location: Lambourn Posts: 631

I would imagine a 110 wouldn't be prone, and I did drive that 50th pretty hard! I dug out a video of climbing up Stile End in the Lakes back in 2009 before it was graded. The ATB in the back is working very well and I was crawling up there and letting it just do its stuff. Apologies for the music and video quality - it was a while back. Forward the video to around 3:52 starting at the squeezy gate...  JB @Lodelaner Instagram Youtube greenlaning and other LR related content

20th Jul 2023 2:59pm

geobloke Member Since: 06 Nov 2012 Location: Nottinghamshire Posts: 4410	Funnily enough I have just stuck a historic video with an equally interesting choice of backing music into the miffy thread https://www.defender2.net/forum/topic53859-615.html Yes I expect you are quite right about the 110, certainly others rate the setup in their 110.
20th Jul 2023 3:10pm

jimbo55 Member Since: 15 Jul 2020 Location: Midlands Posts: 398

I think that Nigel is trying to prevent people breaking loads of other parts without thinking, if you drive with some mechanical sympathy and don’t keep spinning the wheels then there’s not reason as to why by fitting a locker/atb you’d need upgraded shafts. It’s not usually the torque that breaks shafts or cv’a, it’s shock loading when a spinni mg wheel suddenly gets traction. I ran a rear locker for 2 years in my old 300tdi and I’ve had twin lockers in my tuned td5 for the last 7 years. Both on 33” tyres and above, a fair bit of hard off-roading and abuse in that time. I have only used standard shafts and cv’s and touch wood never broke one. I maybe overly mechanically sympathetic, but would much rather lock the diffs and crawl though somewhere than be spinning wheels and using excess momentum.

20th Jul 2023 5:00pm

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