Help - Disposable diff syndrome. My 200Tdi is eating them

[omara04]

Hello all. I was after some opinions / advice on what to do, and if anyone else has had (and cured) a similar problem.

My truck is a 1993 200Tdi disco, and i've put a +2" lift and 265/75 16 Insa Turbo Special tracks;  I keep destroying rear diffs. Additionally I've uprated the pump through tweaking, and increased the boost on the blower to get a bit more oomph.

However, the problems didn't start until I got the big tires. The first diff was a 10-spline, and that began to wear rather rapidly until one day it went pop when I was offroading. I replaced that with a 24-spline unit (supposedly able to handle more torque), and that went in a similar fashion, this time without any warning.

2nd hand diffs change owners for about £50, but I don't want the hassle of continually replacing them.

So I wondered what anyone else had done? Mr Alford (also on here) has exactly the same mods (save for the increased fuelling) and he's yet to even put a scratch on his diff, and now I'm on my 3rd. I've heard talk about 4-pin diffs being virtually unbreakable, but then does that mean the next "weakest link" in the chain will simply break instead? e.g. halfshafts, transfer box etc. etc.?

Any advice welcomed!

Ta

[discowoman]

driving style? prop twisted out of line? lack of oil?

[stewy1984]

i'd say its the special tracks mate, ive got the same mods but just use 265/75 m/t's and have had no diff problems yet.

[Benjamin]

Those tyres grip like hell.  Try less revs  =; let the tyres do the work  :-k

But if you cant help your self like me fit a air locker and ashcroft shafts!

Where do the diffs normaly go? Crown and pinion or planetary gears? Exsessive wheel spining will build up heat in the planetary gears and weeken them. Crown and pinion failer can be down to worn barings or just too much load. pegging the crown wheel can help to prevent this.

[Disco-Ron]

Tyres and driving style i'd say..... i fitted 285 75's on my disco, and did 3 diffs in almost as many weeks..... now gone back to 235 85's, and no more probs... he says touching wood......... also, don;t just sit spinning the wheels, diffs don;t like it!!

[Range Rover Blues]

Who told you 24 spline diffs could handle more torque? it's rhubarb.  A commonly held oppinon is that 24 spline halfshafts are stronger or less prone to fail but that isn't your poblem.

In fact yours is odd, we'd not be surprised if you were trashing halfshafts, the next weak link in the back and might then be the crown wheel jumping sideways (needing pinning).

Anyhoo, a 4 pin diff will be a good idea, or an ATB if funds allow.  Top of the shop an ARB locker, then you really will start to bust halfshafts, so get yourself an X-Tool too.

[BK]

Lead foot?? :lol:

[stuntman]

A mate of mine is also on diff no3, with insa's and lift, fuel and boost tweak.

I have to say it is deffo his driving style 

[omara04]

thanks for all your info guys - as you rightly say it's some combination of the tires and the driving style. In particular, the diffs have gone crunch at times when I was being in a  particularly stoopid testosterone-fuelled moment. :roll: I think in the short term I'll get another diff and just tone it down, until such time I can afford a 4pin one or a locker. To be fair, I've never broken anything RTVing, so I guess either I'll stick to that, or take things a whole lot easier.

I'd be loathed to get rid of the insas, because they are just incredible tires that get you so much further than anything else.

The only concern I had about going for a 4 pin, was then you could be looking at transfer box shafts and gearboxes galore. Anyone any experience of fitting a 4-pin and then breaking something else instead?

I also carry a lot of CRAP in the boot that could do with being sorted - tools, jacks etc. Maybe i'll take the rear seats out and shove the weight farther forward.

Regards the torque a 10 vs a 24pin, I got it from a site that linked to ashcroft transmissions (can't find it now) but it said something along the lines of a 10pin diff is good for about 3,000Nm wheras a 24 pin is good for about 4,800Nm...

[Range Rover Blues]

Fix the diff, next to break will be the half shafts.  Somethings got to give, let it be them.

[omara04]

Where do the diffs normaly go? Crown and pinion or planetary gears?

Last time it was the planetary gears. I've yet to strip this one, but i reckon it'll be the same as i've jacked it up and both wheels spin freely and cleanly whilst the prop does not.

[omara04]

+00

Fix the diff, next to break will be the half shafts.  Somethings got to give, let0 it be them.

0
quite right - at least then it's £35 a side and only  minutes with an x tool,as apposed to £50 and an hour or two!!!

[Range Rover Blues]

That sounds like the crownwheel then, unless you had the handbrake on.

[Steve ray]

Fitting second hand diffs ......... might just be unlucky, but given the grip levels of the tyres - likely to be that 'loading' the Diff and causing it to break.

Options?

Cheaper than an ARB, consider stick a Detroit locker .......... should be stronger and you'll get to more places without the need to "throw" the motor at the scenery. Only disadvantage on a Detroit, is low speed manouvering in very slippy mud - tends to want to push the motor straight on.

www.crowndiffs.co.uk
speak to Steve ..... lots of good advice, whether you decide to buy one from him or not

[Range Rover Blues]

I had a Detroit and got rid of it for the reasons Steve mentioned, when grip is low they can make things worse not better.

My advice (that's all it is though) is a truetrac ATB style diff, hugely strong but a bit more forgiving than a Detroit.

Either way I can't fault Crown diffs, got to be worth a call.

[CNorman]

Surelly a 24 spline diff would be tougher than a 10. Your meshing 24 parts of metal, not only 10!

[extreme90]

no
he is siezing up the pins that the sun and planet wheels run on due to excessive wheelspin ect ect
then once nipped up, shaft breaks gubbings drop out  :lol:

this milarky about 24spline being stronger than 10 spline is aload of twoddle
only difference being the amount of splines are on the planet gears
the suns, pins, ring and pinion are all the same

go to hell with it, fit a ARB problems solved  :lol:
4 pin diff and a air locker all in one so you can go further than the rest can  ;)
dan

[Range Rover Blues]

Completely agree with Dan.  24 spline only gives a (slight) advantage in the streegth of the halfshaft and that comes at the expense of durability.

As you aren't busting half shafts yet then 24 splines is a red herring.

Fit a locker, any locker and you will stop the problem Dan is describing.

[omara04]

Thanks for all your advice guys. I've spoken to Steve at Crown diffs and he was very helpful. Just to get the truck back on the road I'm going for another 2nd hand one, hope for the best and take it real easy, take out some junk out of the back, throttle back the diesel pump, and reduce the "mental moments" to a bare minimum. In the meantime, i'll be saving my pennies and going for some sort of locker or a 4pin jobbie, so that when the next one breaks I can afford to do the job properly!

Re: the strength of axles, it wasnt just an off-the-cuff remark, i've got a link to a page (which annoyingly is on my work computer so I'll have to get tomorrow) which states that the 10 spline can take x amount of 1,000s of Nm, whereas the 24 spline was re-designed and can take x ++ amount of 1,000s of Nm because of the extra material in contact with the halfshaft. Of course, the information is only as reliable as the source, but it would seem rather far fetched to fabricate truth to that level of detail.

Steve

[Range Rover Blues]

Steve, I'd be interested to read that if you can find the link.  The only part that is different is the centre of the sun gear within the diff and the end of the halfshaft, which is the part that brakes.  Typically the root of the splines starts to twist then snaps.  I guess that because the 24 splines are not as deep that there is more metal at the OD of the shaft where most of the strees is, in theory you could say it's stronger but they may also be heat-treated like the 10 spline units that Ashcroft's used to sell (I'd have those if they still made them).

The downside with 24 splines, now that they are starting to wear is beacues they have am angular contact face rather than a square one, once they have worn they jump, both the gear and the halfshaft are then wrecked.  Whilst 10 splines do wear it really just weakens the shaft as there's less metal in it, plus is causes backlash which is very annoying as I know first-hand (my diffs need to go to Crown soon).