Likely cause please?

[lneil]

I found I'd lunched the ring & pinion in the front diff, which had punched the small hole out the bottom of the alloy housing.

Outside housing:


Inside housing:


Pinion:


Ring gear:


Spare bits swimming around inside:


What is likely to have caused this?

[TJ]

Shock load, trying to recover somebody may be. Or just metal fatigue / failure.

[Bulletproof]

Has the diff done a lot of Ks. ?

Nearly all diff failures are through tolerances getting out side there limits. I know of many hilux diffs breaking but I also know of many others running huge tyres and never breaking a diff. The main difference why some break and other dont is because like myself we pull our diffs to peices once a year and reset the preloads and backlash between the crown wheel and pinion.
Yours may be just metal fatigue.
Cheers Richard

[lneil]

Thanks.

Standard open 5.12:1 factory Escudo manual front end, not carrying any excessive shock loadings that I was aware of on that trip. Done about 125,000 kms.

The diff' has never been apart since we've had the truck (2 years, with plenty of hard use). I have never understood diff's so just regularly changed the oil and left it at that. I guess I'll have to learn how to set them up so I can adjust them regularly then!

I might have to pick your brains Richard when I get a new housing, and rebuild this one as a spare.

[Bulletproof]

Thanks.

Standard open 5.12:1 factory Escudo manual front end, not carrying any excessive shock loadings that I was aware of on that trip. Done about 125,000 kms.

The diff' has never been apart since we've had the truck (2 years, with plenty of hard use). I have never understood diff's so just regularly changed the oil and left it at that. I guess I'll have to learn how to set them up so I can adjust them regularly then!

I might have to pick your brains Richard when I get a new housing, and rebuild this one as a spare.

I have most of the gear to set diffs up but I don't have the specs for your Escudo.

I live at 532 Main Rd hope on the top of Burkes Bank. Feel free to drop in or me give me a call on 5448836 and I may be able to help.

Cheers Richard

[lneil]

Cheers Richard, I will.

I've seen your truck parked outside often! I'm just in Richmond so only minutes away.

[KiwiBacon]

First thing is find out which broke first, the ring or the pinion. Then the spare part took out the rest.

If it was fatigue, take a close look at the fracture surface. You'll see an area of final fracture and up to that radiating lines where the crack started and slowly grew through the tooth with each use. Follow the radiating lines and you might be lucky enough to see where the crack originally started.

[Flash2004]

I'd take a punt and say its not metal fatigue nor shock loading that's done this damage. I've scewed 7 diffs on three different vehicles over the past few years and none look anything like that in terms of the damage done. I'd be looking for a piece left over from an earlier episode with a former owner, maybe a spider gear tooth or part of one, which has got in there between ring and pinion and caused that damage.

I'd also totally disagree with pulling your diff once a year too, the most damage to replacement diffs is caused by abuse (as in my case) or by a poorly set up diff. Once its set up properly though, its done. No need to ever do it again if you got it right and few do unfortunately because its almost a lost art. Modern diffs just never die in normal use. Just keep the oil clean forever after.

[Bulletproof]

I'd also totally disagree with pulling your diff once a year too, the most damage to replacement diffs is caused by abuse (as in my case) or by a poorly set up diff. Once its set up properly though, its done. No need to ever do it again if you got it right and few do unfortunately because its almost a lost art. Modern diffs just never die in normal use. Just keep the oil clean forever after.

I agree that under normal conditions once a diff is set up it should last for years, even the life of the truck.

The problem is that most diffs today have collapsible spacers on the pinion instead of the solid spacers and shims to hold the correct preload on the pinion. Four wheel driving subjects the diff to extremes and a diff under load only has to hit a rock on the flange and the collapsible spacer comes loose and with no preload on the pinion the diff is now ready to self destruct.

That is why many four wheeler fit solid spacers and shims. The Stockton Coal mine is doing this to all their trucks.

Cheers Richard

[dazza85]

xx snip xx
I'd also totally disagree with pulling your diff once a year too, the most damage to replacement diffs is caused by abuse (as in my case) or by a poorly set up diff. Once its set up properly though, its done. No need to ever do it again if you got it right and few do unfortunately because its almost a lost art. Modern diffs just never die in normal use. Just keep the oil clean forever after.

I think that the key here is "normal use" which is why people that do a lot of off-road stuff and lets face it a few people manage to do things with their trucks that pushes them to the limits eventually something is going to give ...

and as BP said there is the adjustments required to compensate for wear

[tallsam66]

I think they are just a weak diff....they were never designed for real serious 4wding...if they werethey wouldnt be alloy.
Slip in some hilux diffs...youll never break one of those in ya susuki.

[lneil]

I think they are just a weak diff....they were never designed for real serious 4wding...if they werethey wouldnt be alloy.
Slip in some hilux diffs...youll never break one of those in ya susuki.

Yeah, the housings are well known for their weakness. The internals, however, are generally regarded as pretty indestructable. That's why I was suprised to find it was not the housing that had caused the mess.

So far I've been unable to find anyone who's seen a standard 5.12 R&P do this!

[SMOKEY]

Give Dave Taylor at Falsgrave Auto Spares a call, 033662374. I think he has a modification he does to these diffs, he ran Vitara internals in his 413 housings in his old Zuk. Mention my name (FITZY) and he might help you out,

AND THEN CHARGE YOU DOUBLE ,

FITZY.

[Flash2004]

I'd also totally disagree with pulling your diff once a year too, the most damage to replacement diffs is caused by abuse (as in my case) or by a poorly set up diff. Once its set up properly though, its done. No need to ever do it again if you got it right and few do unfortunately because its almost a lost art. Modern diffs just never die in normal use. Just keep the oil clean forever after.

I agree that under normal conditions once a diff is set up it should last for years, even the life of the truck.

The problem is that most diffs today have collapsible spacers on the pinion instead of the solid spacers and shims to hold the correct preload on the pinion. Four wheel driving subjects the diff to extremes and a diff under load only has to hit a rock on the flange and the collapsible spacer comes loose and with no preload on the pinion the diff is now ready to self destruct.

That is why many four wheeler fit solid spacers and shims. The Stockton Coal mine is doing this to all their trucks.

Cheers Richard

Not trying to be a wiseguy here, but we need a little bit of fact in this equation. Stockton mine is hardly a shining example of how to get the most out of a machine and in fact would be one of the best ongoing examples of entrenched institutional machinery abuse, in the world.

Pinion bearing preload is designed only to compensate for the initial settling in of the new bearings as a diff is assembled and they are intended to be running under a neutral preload once its all settled in. The proof is to set up a diff exactly by the book and take it for a 10km drive. Generally there will be significant heat around the diff head which you can easily gauge by hand. Drive another 250km over a breaking in period and then check your normal diff temperature after another 10km run. If you have set it right, the diff should be only pleasantly warm to the touch. Collapsible spacers were invented because pulling on a spring balance with string wound around the pinion and getting an accurate inch pound reading was too hard for most mechanics. Most handbooks i've happened to glance in these days don't even give a preload setting, just a torque setting for the pinion bolt when using a new collapsible sleeve.

As a veteran of rebuilding at least 500 truck diffs over time - of all types and admittedly many years ago - I'd hazard a guess that the clever guys replacing collapsible spacers with solid spacers and shims are pulling the $75/hour wool over someone's eyes, probably yours if you let them. I have never, ever seen a mechanic yet, who when setting up a diff, doesn't get fed up with assembling/stripping/reassembling over and over who doesn't go "stuff it, that's near enough". I don't include guys who do diffs every day for a living and have learned exactly what to do, but who does that any more?

[Flash2004]

(deleted) ....a diff under load only has to hit a rock on the flange and the collapsible spacer comes loose and with no preload on the pinion the diff is now ready to self destruct.

Cheers Richard

I'd like you to think really hard about that statement Richard. Of course the flange could take a hit, but to claim it could/would loosen the preload in some way without first bending or breaking off the pinion shaft is a very big statement. I've thought about it, and I say its an old wives' tale.

[wopass]

put some belzona over the hole to stop oil leaking out, grind the jaged edges off the teeth to take and cracks and stress risers out, then bang it back in with some nice new oil and carry on for another couple years while you find another one for a spare

done that before ...it was a 40 series diff tho

[Bulletproof]

(deleted) ....a diff under load only has to hit a rock on the flange and the collapsible spacer comes loose and with no preload on the pinion the diff is now ready to self destruct.

Cheers Richard

I'd like you to think really hard about that statement Richard. Of course the flange could take a hit, but to claim it could/would loosen the preload in some way without first bending or breaking off the pinion shaft is a very big statement. I've thought about it, and I say its an old wives' tale.

I have seen it happen a number of times.

The secret of not breaking any diff is no slackness at all,especially the pinion.In the 90s all the toyota 8 inch diffs were upgraded with bigger bearings to take away from any movement that was happening with the older diffs .

Any one who runs big tyres and extra power needs to keep all preloads at the max readings rather than min. Jaffa for example with his truck on 40inch tyres has his preloads set twice as much as the service manual and many other rock climbers do the same.

It is impossible to set a pinion preload going solely on the torque setting of the flange nut. You have to have min torque setting here but at the end of the day it is preload that counts and this can be done with a small torque wrench.

I have a complete set of 10 cruiser shims and a solid spacer and use these on mine and touch wood have never blown a diff.

Richard

[Flash2004]

In the face of such compelling logic, who are the differential designers and manufacturers to specifiy any different? What would they know anyway. What would highly trained, qualified and paid transmission technicians who make it their business to completely understand the workings and stresses involved know about it. What would you do with the extra 20 engine horsepower that it would take to drive a needlessly overtightened pair of diffs anyway?

The only meaningful thing any Joe Bloggs can do to try and save his diff from overload failure is to drive correctly and keep power inputs and shock loadings (which are what do the damage) within its mechanical limits. It may be possible to reduce the tooth backlash to a minimum if your crownwheel is absolutely true and in off road applications where heat buildup - which is what the backlash is also designed to accommodate - is not an issue. The fact that you have never blown one to date Richard, which is a pretty good record, probably stems more from your awareness of the overload situation with your big tyres than through any mechanical thing you've done. If you drive yours any continuous distance, I'd say you could use your diff housing for a cigarette lighter if you have it that much overpreloaded.

Don't forget the old saying "if all else fails, read the book!"

[Flash2004]

put some belzona over the hole to stop oil leaking out, grind the jaged edges off the teeth to take and cracks and stress risers out, then bang it back in with some nice new oil and carry on for another couple years while you find another one for a spare

done that before ...it was a 40 series diff tho

After another look at it I tend to agree this idea could work. You'll need some patience and a small diamond stone to make sure there are no raised local pressure points though. What's to lose if you do it yourself? It gets you time to find a good deal on a replacement already set up, Its in the front, presumably you have free wheeling hubs for road work?

[Bulletproof]

In the face of such compelling logic, who are the differential designers and manufacturers to specifiy any different? What would they know anyway. What would highly trained, qualified and paid transmission technicians who make it their business to completely understand the workings and stresses involved know about it. What would you do with the extra 20 engine horsepower that it would take to drive a needlessly overtightened pair of diffs anyway?

The only meaningful thing any Joe Bloggs can do to try and save his diff from overload failure is to drive correctly and keep power inputs and shock loadings (which are what do the damage) within its mechanical limits. It may be possible to reduce the tooth backlash to a minimum if your crownwheel is absolutely true and in off road applications where heat buildup - which is what the backlash is also designed to accommodate - is not an issue. The fact that you have never blown one to date Richard, which is a pretty good record, probably stems more from your awareness of the overload situation with your big tyres than through any mechanical thing you've done. If you drive yours any continuous distance, I'd say you could use your diff housing for a cigarette lighter if you have it that much overpreloaded.

Don't forget the old saying "if all else fails, read the book!"

I Want to make it clear I am not telling anyone to go outside factory specs for average use.

The rock crawlers are trailer queens so heat build up is not an issue so they can run very tight tolerances.

I have a hilux. The specs say the pinion preload should be 3-5 Nm so I set mine at 5, The back lash should be 5-7 thou so I set mine to 5 and the carrier bearing preload is 1.5 holes on the adjusting shim so that is what I stick to.

As part of my tool box in the truck I carry a heat laser to measure bearing temperatures and the pinion has never been too hot .

"Reading the book" only makes the job sound hard. It is quite simple with only 3 things to be really fussy with. All you need is a dial guage , a 200+foot lb torque wrench for the flange and a small 1-20 Nm torque wrench for the pinion preload.

Cheers Richard

[vvega]

(deleted) ....a diff under load only has to hit a rock on the flange and the collapsible spacer comes loose and with no preload on the pinion the diff is now ready to self destruct.

Cheers Richard

in rally cars that tend to colapse the spacers .. we set up the diff to factory specs... then remove the spacer measure it and replace it with a non colapsobile one for this very reason .. but its not rocks that damage it.. its the coninial grip no grip situation under load that rally cars are operated under
i dont see how it would be any different for a off road truck ..
please remeber i dont know arse from kite about 4 wheelign .. but i have worked on many many race cars both tarmack and rally.. and im guessing that that you encounter all the same issues with traction