 | Home > Technical > Diff failure caught just in time ! |
 
|
|
|
| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16876   
|
But it isn't the action of the differential that is destroying these. This failure is due to the deformation of the diff carrier where the cross-pin fits, which leads to the cross-pin moving, the retaining roll-pin failing, and the cross-pin dropping out. remember that the entire traction power to the halfshafts is transferred through the carrier to the cross-pin, and thence to the halfshafts via the differential side gears. That pin is bearing the brunt of circa 50% of the engine output (because it is split 50:50 front and rear) all the time. Lcok the centre diff and loose traction on one wheel, and the pin at the opposite end is transmitting 100% of engine power.
Remember that the pins do far, far more than just support the differential gears, they transmit the drive power to the halfshafts, something that is often overlooked. the failure depicted in the video is entirely different to that which destroys Puma diffs. In the video, with one wheel spinning excessively, the two differential gears (assuming a standard Rover pattern diff) will be spinning very fast on the pin. Eventually the plain bearings in the differential gears will seize on the pin, the pin will rotate, and the diff will fail. This is not what is happening with our Defenders. If this failure mechanism has occurred, I would expect the hole in the carrier to be damaged but I would not expect the carrier to have become slotted. The only way to "slot" the previously round hole in the carrier is to apply a cyclic acceleration and retardation to the driveline, which effectively cycles the load between the pin and the carrier. Accelerating and decelerating will do this, but the lumpy nature of the TDCi motor will also do it, probably with a frequency twice that of the engine's rotational speed (since there are two "bangs" per revolution on a four-cylinder four-stroke engine). There is no doubt whatsoever in my mind that the video shows an entirely different but probably much more common mechanism to that which spells doom to Puma diffs. The evidence is clear! Last edited by blackwolf on 29th Jun 2021 1:33pm. Edited 1 time in total |
||
29th Jun 2021 1:21pm |
|
| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2231 
|
I am sure I previously saw a thread on here showing the differences between '2 pin' and '4 pin' diffs (and an explanatin of the ambiguity in terminology)
Can anybody point me in the right direction? I want to identify a 2 pin and 4 pin by sight > 110 XS Double Cab > Instagram @simonlanemind |
||
|
29th Jun 2021 1:32pm |
|
| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16876
|
The terms "two pin" and "four pin" are mysterious, since both are technically nonsense and misleading but in widespread use.
A so-called "two pin" diff has two differential gears which are carried on a single cross pin in the diff carrier. The photos immediately above this post in Jamie W's post are of what i call a "two gear" or "single pin" diff but most call a "two pin" diff. You will find one of these front and rear in a 90 and in the front of most 110 and 130 Defenders. A "four pin" diff, which is an equally nonsensical term, has four differential gears supported usually on a cruciform pin, or sometimes on two pins notched to allow them to cross in the centre. I call this a "four gear" diff, it actually has four gears on two pins, but if you call it a "two pin" many people will be confused (more confused than they usually are). Because of the construction of a "four gear", the differential gears and side gears (of which there are always two irrespective of the number of differential gears) are almost always fully enclosed in a bolt-together carrier and cannnot be seen without dismantling. The easiest way to tell which type you have is to work on the assumption that if you can see the differential gears and can only see two, you have a two-gear diff. If you cannot see any of the differential gears, only a solid looking carrier, then you have a four-gear diff or possibly an ATB or full locker, which tend to look the same. A two gear diff looks like this:  Click image to enlarge A four-gear diff looks like this: Click image to enlarge This may be the thread you're thinking of? |
||
|
29th Jun 2021 1:40pm |
|
| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2231
|
Ideal thanks. So the weaker type has an open casting through which you can see the gears whereas the strong type looks like more of a machined unit enclosing the gearing
Is it possible to identify which is fitted by looking through the axle filler hole? > 110 XS Double Cab > Instagram @simonlanemind |
||
|
29th Jun 2021 1:50pm |
|
| Angus_Beef Member Since: 30 Apr 2015 Location: Oslo Posts: 434  
|
you can indeed see the carrier through the fill hole
 Roaming around 🇳🇴🇨🇠|
||
|
29th Jun 2021 2:04pm |
|
| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2231
|
Nice thanks. And a final question before I stop hijacking this thread... Can front/rear long nose diffs be fitted interchangeably? > 110 XS Double Cab
> Instagram @simonlanemind |
||
|
29th Jun 2021 2:06pm |
|
| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3206  
|
I re check the pics from the OP, and you are right.. the mushrooming or the carrier hole is like an old chisel head. Other than the tdci being more 'cyclic' there are 2 more important differences to the Td5. 1. Halfshafts are thicker, and so must have more torsional rigidity. More rigidity means more brinelling effect on the whole drivetrain. Drive flanges being the most affected. 2. The weird geometry of the propshafts, being a nose up installation, with the inherent harmonics in the driveline. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
||
|
29th Jun 2021 2:24pm |
|
| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3206
|
Yes, they are the same. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
||
|
29th Jun 2021 2:25pm |
|
| Supacat Member Since: 16 Oct 2012 Location: West Yorkshire Posts: 11018 
|
I have in my mind that this was a recall?
My theory would be to do with foreign markets, particularly the US and the role of the NHTSA in mandating publication of certain manufacturer communications. As much as I have looked, I cannot see who or how recalls in the UK are managed.
Some of the "engineering" solutions are equally laughable ~ drilling holes and draining oil filled bushes because they are "noisey" and my favourite is the solution to oil dripping out of an intercooler... fit an o ring so it's harder for the oil to get out. |
||
|
29th Jun 2021 4:52pm |
|
| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2231
|
Had a look and rear is a four gear, front is a two gear so that’s half good news
 will keep my eyes peeled for an upgrade
I understand the principal of ATB/LSD/lockers but is there any benefit to fitting these in place of an open diff to a primarily road going vehicle given the traction control? > 110 XS Double Cab > Instagram @simonlanemind |
||
|
29th Jun 2021 7:28pm |
|
| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16876
|
Your 110 rear will be a 4-gear P38 diff, not a Rover pattern.
Re. the ATB question you will find conflicting answers. Those of us who have them generally will say yes, there's a benefit. Those who don't have will say there's no benefit. In all honesty the main benefit on a TC-equipped road-going motor is that they are significantly stronger than the stock diffs. The LSD aspect is probably insignificant in these cases. |
||
|
29th Jun 2021 8:11pm |
|
| ashtrans Site Sponsor Member Since: 08 Nov 2008 Location: Harpenden Posts: 254
|
a question for those that have had the cross pin hole elongate in the 2 pin carrier,
do you have traction control ? this works by the braking system slowing down the wheel thats spinning and in turn transferring the drive via the diff centre to the wheel thats not turning. This would put a huge load on an already weak diff centre and the ABS pulsing may well be hammering the hole oval Dave |
||
|
29th Jun 2021 8:51pm |
|
| ashtrans Site Sponsor Member Since: 08 Nov 2008 Location: Harpenden Posts: 254
|
on the same subject, the ATB's and traction control work great together,
the TC kicks in far less often and when it does, it 'left foot brakes' so the ATB transfers more torque to the wheel not turning. not quite as good as lockers but not far off, Dave |
||
|
29th Jun 2021 8:53pm |
|
| LR90XS2011 Member Since: 05 Apr 2011 Location: bickenhill Posts: 3613 
|
I love it when Ashtrans and Blackwolf join a thread as thier knowledge is invaluable,
It is the input off you guys the led to me installing 2 Ashcroft ATB diffs to aviod any live threatening future diff failures, love the reduction in play and the planted feel compaired to open diffs. constantly looking for an excuse to do the transfer box as well. A def2 discount on the required item may just clinch it. DEFENDER 90 TDCI XS, I hope everyone is well and your land rovers make you happy |
||
|
29th Jun 2021 9:05pm |
|
|
|
| All times are GMT + 1 Hour |
< Previous Topic | Next Topic > |
Posting Rules
|
Site Copyright © 2006-2024 Futuranet Ltd & Martin Lewis
