 | Home > Technical > ATB (torsen) front and rear install |
 
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436   
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Torsen diffs, the most mis-understood and underrated diff … to my opinion.
Just installed a front and back one on the 110 and …. Wow! I wont go into the particulars of how torsen diffs operate, google and you’ll find hundreds of pages nicely explaining this. Just want to give my impression as most of the time you only find arguments compared to full lockers. I placed the ATB's as my rear diff went out and i do not have use for full lockers, but can use the full time extra traction ATB's give. Looooong text, hope it helps someone. To get the mostly found misunderstandings out of the way: - a Detroit locker is not a torsen diff , it is an un-locker - torsen, which is a LSD as it is not a full locker, has nothing in common with the classic friction plate based LSD’s which operate rotation speed based I tend to categorize them in corrective and preventive aids. Friction plate LSD and TC are corrective aids; they react once traction is lost Full lockers are both preventive and corrective, depending on when you switch them on. But they are a passive system as they need to be switched on. ATB’s are preventive, they transfer torque before and during loss of traction. The main catch between both is that the first 2 are taking power, by slip or braking; so they work against the power you put into it, to regain traction. The ATB’s do not. They transfer the power without consuming or braking it. Why an ATB ? This all comes down to personal choice. With 90% road driving, of which 60%pulling trailers I was looking for an aid to help out in winter on the road but also offroad and at all times. Without the need to switch it on as stopping on a snow covered hill with a loaded horsebox attached is not an option. Keep traction and momentum, no time to switch things on or off. (TC slows me down too much in those situations. Mountain area, so hills are not 7% fake flats) Friction LSD’s burn their plates within months in these conditions, so they were out of the question. My previous experiences with truetracs were very positive. So I was already biased to them. On top of that I am limited to normal size tires, as otherwise the trailer wont attach, I do not want to compromise road handling by putting an aggressive tire. And I don’t want to further invest in HD drivetrain components. My offroading is limited to greenlining type of things, not competition mud. A Detroit in the back, which is a popular choice is a possibility but I voted against them as their on-road behaviour is questioned and again, there seem to be quality issues in the last years. Regarding installation of the diffs, I did mine (front and back) in 8 hours, including a lunchbrake. Nothing really difficult just don’t rush setting the R&P and you should be ok. How-to’s can be found on google. Which ones to choose from? Eaton TrueTrac Quaife Ashcroft ATB I agree with how Ashcroft puts it, the Quaife Torsen is the high level lifetime warrantee top of the bill product, at equivalent price. The truetrac is a simplified design (3 pairs of gears instead of 6) in a cheaper construction, at half the price. The Ashcroft has the design and construction of the Quaife at competitive pricing to the truetrac. (found them to be about 200 euro cheaper actually) Although I had truetracs in my discovery before without problems there are some sites mentioning quality issues with them in the last years. I went for the Ashcroft ATB’s and replaced all bearings and put in a new R&P in the back (as mine was howling as a wolf in heat) Other parts needed: P38 spacer ring (for puma rear diff) Side bearings New R&P (optional) (note: LR changed the teeth design on the rear R&P)
(right side is new one) Pinion Bearings (optional) Pinion Oil seals (optional) Magic Blue (marker for setting R&P) Not worth shopping around, order all from Ashcroft and get the right parts and quality at once. Service was perfect and at least you know the bearings are up to spec and not blue-box. P38 rear diff
Rover front diff
How does it drive? Tarmac - steering a little heavier and eager to come back to the straight ahead position. Nothing annoying, a difference, and not a bad one. - Turning: tendency to oversteer a bit when under power. This sounds worse than it is, nothing dramatic unless you drive as you stole it. (and then the fun starts) You notice this only when changing gear or getting off the power in a turn. The car will pull inside a bit that moment. It is all relative and you get used to this in an instant. (note that this is purely the influence of the front atb and a heavy foot) - overall the car is much more planted and stable. Tramlining absolutely neutral, even when full of water (no tendency to jump out) Aquaplaning almost becomes fun, as it doesn’t happen (so far). It feels much more tight and stable in any condition. - Braking: straight and 100% controlled, better than before. (torsen diffs work under brake force also!!) I cannot get the ABS to come on anymore on dry pavement, so better brakes make sense with these diffs. (not that braking is worse, opposite is true, but as optimal braking is achieved with ABS it would be better if the brakes can actually brake that much that the ABS comes on) In the wet it is surprising how late the abs comes on and how stable and good the car brakes (compare to open diffs) (even when swerving around a pothole on a heavy tramlined road with the 110 loaded and RTT on top it was much more controlled) Not to forget the 110 is stock and only has 75000km, so even more effect for worn or lifted vehicles. - TC: while TC would come on now and then I provoked the hell out of it both on dry and wet tarmac and didn’t have it come on once. Even drifting (yes now you can) roundabouts does not switch it on. (squealing tires however…  )
- Pulling: waited a couple of days for things to settle in. With the trailer the more stable drive is even more noticeable. The 110 pulls with confidence and the trailer is not juggling at the back. Esp when tramlining (horsebox has wider track than defender, which most of the time leaves or the defender or the trailer in a track on dual carriage ways) Pulling away on gravel and grass is absolutely more fluent and without spin. (almost boring) Note: Some people mentioned reversing problems with eaton diffs, this does not apply to ATB’s but to the Detroit unlocker. I also did not notice any influence while maneuvering the trailer. Opinion: A 100% improvement. Also, and this is a big point on the Puma, drivetrain slack is totally gone. I am really surprised how much slack the open diffs had. As the gears in an ATB are not settable and compensate themselves for wear I expect this to be something for the long run and not a side effect of having new parts installed. Offroad greenlaning Been doing a bit of very wet lanes in the past days. How to compare it… First of all, the signals to engage difflock come way way later. Ridiculously late… Whereas engaging difflock is normally an automatism coupled to “now we go offroad” it now is more of a switch to engage more, something as switching on a locker when facing a bad stretch. With difflock engaged the oversteering becomes more obvious, but is controllable. (talking powering through a stretch) I also noticed that once you pick a line with confidence you much less have to correct to stay on that line, the 110 seems more confident and planted. Putting down the loud pedal is only improving this. The main observation though is that when driving normally as in as slow as possible and as fast as necessary the ATB’s take you double the distance without drama. In reality you hardly realize that without them you already had to engage some driver skill to get that far. IMPRESSIVE is a good word. TC: comes on only 10% of the time compared to open diffs. Braking: sliding mud slopes are a bad environment for AT’s and ABS but here again the ABS does not interfere as much as it does with open diffs. While the switch to power off the TC/ABS was worthwhile before I would not really consider it putting with the ATB’s. You’ll benefit more from the TC helping out engaging the ATB when a wheel is in the air than from not having TC to save the brakes / keep having power to the wheels. Maybe in sand it still makes sense, need to test. Also, with the anti roll bars installed you get to a wheel in the air situ much earlier, where the TC comes to help. I should also mention that I noticed driving much faster than before. Not always a sensible thing to do but as it drives so much better and controlled it’s hard to resist. Reversing: big surprise and advantage. Reversing on a slope is absolutely a no thrills thing now, where it used to be nearly impossible before. (once wheels started spinning sliding sideways etc) All the above observed on 235/85 BFG AT tires. Guess that’s another argument in favor of the ATB’s. I also went back to my 45° grass slope at the reservoir nearby. Taking the hill at idle in all combinations (which is impossible as not enough grip) got me halfway up….. normally the 110 would start spinning the moment the rear tires reached the start of the slope. Driving it up in 2nd low with some momentum was as driving up paved road… No TC, no slip, no drama. You can even accelerate and decelerate while driving up. VERY impressive. Life test Well, cannot speak for the Ashcrofts after a couple of days. Time will tell. But I do know that my discovery with the truetracs, which is heavily abused by its new owner, is still going strong after 5 years. (and that’s a tuned 4l V 
My expectations are high. As said the construction is much better and stronger than the truetracs. Side argument 60/40 torque split only, not 100% as with a fill locker, means no need to upgrade halfshafts etc Opinion Underrated. If you are not talking trophy style events, where full lockers make sense, this is a very sensible upgrade. The ultimate for me would be the ATB in a KAM rear locker. Hmmm…. 
Even without TC, the little situations where you’ll need to apply some braking to engage the ATB’s are not compromising the benefits these diffs give you. For me double ATB’s (= price of 1 full locker, or a stock LR supplied reppacement diff) give me: - improved road handling, all the time - improved offroad performance, all the time - improved safety, all the time - less wear on TC involved components, (some Aussie axle manufacturer claimed life of a diff with TC on is between half an hour and one hour before the metals starts disintegrating) - no need for a second set of tires or a compromised road behavior with muds - no need for upgraded drivetrain. As someone wrote on a forum, the worst thing with these full time working ATB’s is that you’ll have to continuously listen to those that went for full lockers finding excuses why they spend 3 times as much for something they use 2% of the time. So I hope this wont start another which is best discussion as I wrote this only to shed some light on an underrated great product. :) Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated  |
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15th Jun 2012 11:58am |
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| Naks Member Since: 27 Jan 2009 Location: Stellenbosch, ZA Posts: 2645  
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thanks for the write-up
how much did these set you back? -- 2010 Defender Puma 90 + BAS remap + Alive IC + Slickshift + Ashcroft ATB rear 2015 Range Rover Sport V8 Supercharged
Defender Puma Workshop Manual: https://bit.ly/2zZ1en9 Discovery 4 Workshop Manual: https://bit.ly/2zXrtKO Range Rover/Sport L320/L322/L494 Workshop Manual: https://bit.ly/2zc58JQ |
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15th Jun 2012 12:35pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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Naks,
if you dont replace R&P (around 150£) and pinion bearings (around 30£) Diffs 295£ Bearings 20£ Spacer ring for rear 32£ So all together both front and back 662£ ex vat While you're at it put another 100 in drive flanges, sealant and pizza.  |
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15th Jun 2012 12:50pm |
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| T1G UP Member Since: 08 Dec 2009 Location: Bath Posts: 3101  
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did you find much play in the LR diff? Is there less backlash then before with thye ATB diffs?
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15th Jun 2012 3:26pm |
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| AndrewS Member Since: 10 Apr 2007 Location: Hereford Posts: 3708  
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Great read
 130's have feeling's as well you know |
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15th Jun 2012 4:17pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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TiG UP,
I'm sure you know but just to avoid confusion, backlash is in this case mostly used as free play on the R&P, which you need to set and which is defined by the pinion washers. I found this to cause less than 5° of pinion movement, so neglect able in proportion to the other free-play points in the driveline. If set correctly backlash of the R&P is the same as before. My rear diff was set completely off, which resulted in the howling sound i had and why i started looking at the diffs in the first place. The total free play of the pinion in the rear diff was between 2 and 3 hours (70°). replacing the drive members did not reduce this, only reduced the free play between wheel and halfshaft. With the new R&P i ended up with about 10°, 1 notch further adjusting the diff bearings made the preload too stiff to my liking. This did not change anything to the clunking sound when changing gear. With the ATB installed and same pinion settings the clunking is gone, completely. The only thing that makes a clonk when provoked is the clutch, but in normal driving it all feels as tight as the brand new 2.2 i drove a couple of weeks ago. The front diff also had 10° pinion movement as it was. After installing the ATB this did not change. But when driving the car without the rear driveshaft i noticed the front would also make a clunking sound when provoked (so much much less than the rear) now with the ATB installed it doesnt. Guess the short answer to your question was yes.  |
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15th Jun 2012 4:21pm |
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| MartinK Member Since: 02 Mar 2011 Location: Silverdale (Lancashire/Cumbria Border) Posts: 2665 
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Really impressed! Great write-up. Thanks for sharing. Defender "Puma" 2.4 110 County Utility (possibly the last of the 2.4's)
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15th Jun 2012 4:29pm |
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| LR90XS2011 Member Since: 05 Apr 2011 Location: bickenhill Posts: 3643 
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thanks I want some! DEFENDER 90 TDCI XS,
I hope everyone is well and your land rovers make you happy |
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15th Jun 2012 5:56pm |
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| Lodelaner Member Since: 04 Feb 2010 Location: Lambourn Posts: 632 
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Having had rear in my V890 and front and rear in a 50th Anniversary - it makes good sense what you're saying.
The only thing I couldn't live with was the power-on under steer/lift-off correction caused by the front Truetrac. Following a very nervous moment on a roundabout in Basingstoke I took it out and sold it. Another minor limitation is on side slopes, the lower wheel can dig in, causing slewing. Overall though, my favourite traction aid that's misunderstood because of its finesse and subtlety. I love the way you keep the throttle on, the car 'wriggles' and it finds traction. JB @Lodelaner Instagram Youtube greenlaning and other LR related content |
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15th Jun 2012 7:51pm |
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| bpman Member Since: 21 May 2008 Location: Oslo Posts: 8069 
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Great write up Tatra, I will be re- reading it
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16th Jun 2012 4:27am |
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| FG Member Since: 01 Apr 2011 Location: Somewhere on the Swedish East Coast Posts: 63  
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Want one too!
/FG |
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17th Jun 2012 4:57am |
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| MK Member Since: 28 Aug 2008 Location: Santiago Posts: 2420  
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So, does the OE pinnion setup come with height shims? Puma 110" SW
............................................................. Earth first. Other planets later |
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19th Jun 2012 1:53pm |
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| tatra805 Member Since: 16 Aug 2011 Location: Dolany Posts: 436
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MK
Yes, and no Rover diff front shim kit various sizes and settable The rear P38 diff has different sizes of shims, but these are tubes around 45mm in length i would guess. Quite expensive per piece and not really mend to shim as with the rover diff. (length steps too big to be intended for this purpose) I did not find any shim sets for this diff and LR doesn't have them either. (not necessary on this diff, i was told) From what I see these tubes are used to set the pinion depending on manufacturing tolerances of the diff nose and within an "acceptable range". Fine tuning is not possible other than playing with the side bearings of the diff core. to me it comes as the rover diff is the original design and the P38 is made with some "ideas" about shortcutting the setting of R&P, maybe thats also the reason why so many are wrongly set. And as a result a different, more friendly angled teeth design on the latest R&P for this diff. a bit of assuming in the above but thats how i see it |
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19th Jun 2012 3:01pm |
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| MK Member Since: 28 Aug 2008 Location: Santiago Posts: 2420
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Thanks. I understand the "non crush tube" is located between the flange and outer bearing. Right? SO, no shims between the pinnion and inner bearing? Puma 110" SW
............................................................. Earth first. Other planets later |
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19th Jun 2012 3:06pm |
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