Front diff yoke movement.

[PeterH]

I've been trying to track down the cause of a slight vibration over about 80kmh, it gets worse at 100kph.
I replaced 3 out of 4 uni joints today, the one under the cross member has a threaded bolt, so I've left it as is for the moment, but that uj seems solid.
I did notice some movement at the front diff though, when I grab the front uj, I can move the yoke up and down, side to side, about 3 or 4 mm.
Is this normal, or is there something going on inside the front diff?
I've never tackled fixing a diff before, could this be a worn bearing, or something coming loose inside?
I'm not noticing any noise, fluid has always been at the correct level.
Any ideas?
Cheers, Pete.

[Hoges]

Hi Pete
there shouldn't be any discernible movement. From your description it seems that the diff pinion is moving in its bearing, or the bearing itself is moving in the diff housing, or the yoke is moving on the pinion shaft.
If you remove the track rod, drain the diff oil, remove the brakes and hub assembly and pull the axles, remove the front propeller shaft, then undo the 10 bolts around the diff casing... you can pull out the diff.

I'd then take it to a diff specialist and get them to fit a new bearing/yoke...
I've never done this repair but it seems feasible for DIY as far as remove/replace if someone with the right tools can do the yoke/bearing repair...
Good luck with it

[PeterH]

Thanks Hoges, great advice as always!
Yes I was thinking that might be the way to go, remove it myself and take it to a specialist.
I didn't think movement was a good thing, I could probably just get the diff center reco'd.
Will have to find a specialist not too far away.

[wayneg]

If you are sure its the diff I would think long and hard about changing the bearings, there are two on the pinion ( 4 pin diffs not sure on 2 pin). I could not source them in Australia even having them in my hand with part numbers. Very expensive, They are shimmed, again a problem getting them. Ended up making them. Why not look out for a second hand diff.

[PeterH]

Good point wayneg, maybe I could drop in a good second hand diff centre instead of recoing the existing one.
Does anyone know if P38 diff centres are all the same through the years?

[Scouse]

3-4mm is an awful lot of movement.
I'm surprised the first sign of this wasn't a massive leak from the diff as the seal would be chewed out in no time.

[Keithy P38]

Thought about a locker? Good time to fit it up if you've ever wanted one...

[clubagreenie]

Just get one of the replacement centres with locker from Ashcroft, this solves all the issues with these diffs doesn't it?

[benji]

Are the front and rear pinions the same? Ie, are the front reverse cut?

[wayneg]

I am 99% sure they are the same front and rear on the Thor cars. Gems cars have 2 pin diffs front and 4pin rear. Even if you fit a locker it aint gona change the slack in the pinion as its shim adjusted. Get a rear from any car or front or rear from Thor. Later defenders have the same diffs

[PeterH]

Awesome info wayneg, I'm thinking of fitting a good second hand one, now I know what to look for!
Most appreciated.

[wayneg]

Just get one of the replacement centres with locker from Ashcroft, this solves all the issues with these diffs doesn't it?
I am not aware of any issues with the P38 diffs, Never heard of any one having a failure.

[Scouse]

Apparently the problem is due to the distance between the pinion bearings being relatively short.
This means that, probably badly worded, they can't support the force transmitted along the pinion shaft as well.

[wayneg]

Apparently the problem is due to the distance between the pinion bearings being relatively short.
This means that, probably badly worded, they can't support the force transmitted along the pinion shaft as well.

This I think is not a P38 issue its a P38 diff fitted to a Puma Defender issue, must be different forces at work. Plenty of P38a`s get noisy diffs after 150000k`s+ but that`s not exactly a weakness

[TheTree]

Just get one of the replacement centres with locker from Ashcroft, this solves all the issues with these diffs doesn't it?

Hi,

That is on my list once I get some other things done, luckily I only have a high speed whine from my rear diff so far!

Steve

[clubagreenie]

The P38 centre is the same in P38 and Defender just the defender seems to report more issues than P38's. Either way, it's a better product, solves the issue, is reverse cut (as far as I'm aware) and has a locker.

Win, Win, Win.

[wayneg]

[QUOTE=clubagreenie;2092004]The P38 centre is the same in P38 and Defender just the defender seems to report more issues than P38's. Either way, it's a better product, solves the issue, is reverse cut (as far as I'm aware) and has a locker.

Win, Win, Win.[/QUOTE

Am I missing something here? I have hands on experience of fitting an ARB locker into a P38a diff. The Pinion is retained, not even touched and the original crown wheel transferred to the locker. How can fitting a locker overcome any pinion bearing issue?
A quick look at the Ashcroft website shows similar fitment to ARB types
Ashcroft Transmissions (http://www.ashcroft-transmissions.co.uk/locking-differentials/ashcroft-locker/ashcroft-locker.html)

[RR P38]

A complete rebuild (bearings) is about $400, you might get it done for less.

[steveG]

Any chance its just a loose nut on the flange?
Probably unlikely, but a quick job to check it before committing to rebuilding/replacing a diff.

Steve

[PeterH]

SteveG, it's definitely inside the diff, the whole yoke moves, the uni joint is new, no movement of the uj at all.
I probably overstated the movement, had a close look yesterday, it is more like 1 - 2mm movement, I was only guessing at the 3 - 4mm I stated earlier.
It has no vibration at all under about 70 kmh, but as you get closer to 80 kmh and upwards it gets worse.
At the moment I'm only driving locally, I don't want to do any big trips until I have this sorted.

[steveG]

SteveG, it's definitely inside the diff, the whole yoke moves, the uni joint is new, no movement of the uj at all.
I probably overstated the movement, had a close look yesterday, it is more like 1 - 2mm movement, I was only guessing at the 3 - 4mm I stated earlier.
It has no vibration at all under about 70 kmh, but as you get closer to 80 kmh and upwards it gets worse.
At the moment I'm only driving locally, I don't want to do any big trips until I have this sorted.

If the nut was to come loose it will allow the flange and bearing to move back slightly along the pinion shaft and allowing radial movement in the bearing.
Yes, the whole yoke would move and the movement would be from "inside the diff", but only because the bearing has been allowed to move away from its cup.

As I said earlier - its unlikely but not impossible. Quick to check and easy to fix if it was though.

Steve

[PeterH]

Just to clarify SteveG, when you say nut, are you referring to a nut inside the diff housing?
If so, I'll definitely check that out, but I have no experience with diffs, I'd need some guidance on what I was looking for if you can offer any advice.

[Outback 1]

He would be referring to the nut which holds the yolk on (outside):)

[PeterH]

Sorry for all the questions, so I'm guessing I'd need to remove the front drive shaft to gain access to the nut in the middle of the yoke?

[steveG]

Yes, referring the nut that holds the flange onto the pinion shaft.

I'm not familiar with the P38 diff so am assuming its pretty standard like other LR diffs.

This is a older style LR diff but gives you the idea:

https://www.aulro.com/afvb/images/imported/2014/02/262.jpg

The shims set the bearing cones the correct distance apart, and the nut clamps the flange and spacer onto the whole lot to hold it together.
If the nut was to come loose then the bearing cones could move apart which would allow play in the shaft.

If the nut is still tight then most likely the bearings are stuffed.

Steve

[steveG]

Sorry for all the questions, so I'm guessing I'd need to remove the front drive shaft to gain access to the nut in the middle of the yoke?

Correct.

Steve

[PeterH]

Well then, I might just have a crack at that tomorrow! Will let you know the outcome. I'm searching for torque values for that nut, can't find any info on this.
Does anyone know what the front yoke nut should be tightend to?

[PeterH]

Looks like the diff drive flange should be 74 foot pounds/ 100 nm from what I can gather for a later model P38, with a 15mm bolt, apparently earlier versions had a nut that was tighter.

[Hoges]

A 12v rattle gun like the ones sold for undoing wheel nuts, is an excellent investment for undoing flange/yoke nuts/bolts. There's a safety issue also in that you don't need a long lever to crack the initial tension... also saves blooded knuckles etc in case something slips... how do I know this...? :angel:

[PeterH]

Got under there today and checked the bolt, sadly it was tight. Tested it with the torque wrench and it did not budge.
So it looks like a good second hand diff centre going in next week.
Will keep you posted.

[steveG]

Bugger - would have been nice if it was a really easy fix.
At least you now know its definitely internal.


Steve

[PeterH]

Thanks for the suggestion Steve, when I had the drive shaft off, I could move the yoke about 1mm in all directions, which would be the cause of my mysterious vibration. Up to about 70 kmh, you can barely notice it, but over that it gets worse the faster I go. Can't leave it like that, will be ringing around in the morning for a second hand diff center not too far from home hopefully!

[PeterH]

I got hold of a good second hand diff today, looks good, feels very solid, but I did discover a chip missing on one of the teeth...what should I do here?
Would it be ok to install as is, or what are my options?

[Scouse]

That diff is stuffed.
Was it sold as a 'good' diff?

[steveG]

I'm no gear expert, but I wouldn't be fitting it in my vehicle unless I was stuck somewhere and had no choice. That "chip" is more like half a tooth missing in my book, and more to the point its half of the actual area the pinion tooth bears against going by the pattern. Easiest option is if whoever you bought it from has a another good one, and is prepared to swap it (or at least take it back so you can source one from somewhere else).
Anything apart from swapping in a good one involves either paying for someone to set it up from scratch or having a crack at doing it yourself. Personally I wouldn't recommend doing it yourself as a first diff job unless you've got lots of patience or someone to look over your shoulder.

Steve

[PeterH]

Yes I'm pretty disappointed to be honest.
I rang around and the guy sourced one from a third party, sold as no returns if it doesn't fit my car, but I did not agree to no returns for a faulty item.
I didn't notice the chip until I got it home up on the bench.
I don't want to fit anything that is not in good shape that's for sure.
I'll be having a word to the supplier tomorrow.
Thanks for the help here gents, it is most appreciated.

[Hoges]

If it wasn't advertised as faulty then the supplier has no option under the law but to refund your money or supply you with an undamaged replacement. You are entitled to expect the replacement to be in reasonable condition /fit for purpose. Where the supplier sourced it from is immaterial. No doubt he put a handling fee or some such on the transaction? In doing so the "contract" is between you and the supplier...good luck ! They can try and wriggle out of it wrt the onus being on you for correct part number etc. But the goods were faulty and they did not make this clear: No Sale!!

[TheTree]

Pete

I agree with Hoges, if it was not made clear that it was faulty, then you are entitled to all your money back

I would not waste my energy installing it and I would be pretty :angry:

Steve

[PeterH]

I spoke to the supplier and he was happy to try and find another one for me.
Waiting to hear back, will keep you posted.

[benji]

It sounds like he's being good. But if he starts to wiggle look up iso9001, every item sold in Australia (including second hand items) is sold with that certification. That's federal law under the trade practices Act.

[PeterH]

Thanks benji, will keep that in mind. I'm beginning to wish I just went and got one I know is there further out of town...I would have had it in and done by now, instead of waiting around for the first one, only to find it was faulty, now waiting for another one. I might see if I can just get a refund and move on.

[PeterH]

Good news, the guy got a good replacement in for me, it's a later model one with the bolt on the yoke, instead of the earlier one with the nut.
Swapped them over today, looks like a much better unit, very little backlash and all the teeth are there this time.
Now to find the time to get it on the car! I'm hoping next week.
Cheers, Pete.

[Hoges]

Glad you got what seems to be a satisfactory result;)
that's a good sign for good result!
good luck with it!
cheers

[PeterH]

Bit of an update for those interested, I spent yesterday and this morning getting greasy under the Rangie today, managed to get the replacement front diff centre in.
Anyone who has done this job would know the fun of trying to wrestle a heavy diff centre into position from under the car!
Took her for a drive, no oil leaks, but I still have a vibration going on after all that.
The nature of the vibration has changed a bit, probably slightly worse if anything.
It's almost as if the tighter front diff is showing up the vibration more, as there is less play in the drive line now.
I can feel it in the steering wheel and in the seat a bit, less on acceleration, more on coasting or slowing down.
I have now noticed 1 to 2mm movement at the other end of the front drive shaft, coming from the tranfer box...I'm guessing the bearing in there is loose too.
Is it possible to replace the front transfer box bearing without pulling the whole transfer box out?
I've replaced 3 out of 4 uni joints, the one I have not replaced seems fine, but it would be a few years old now.
I've put a lot of effort and time into my P38 of late, I must say this is getting a bit frustrating! I'm not up to the point of driving it into one of those car crushers yet, but geez I'd love to get this vibration sorted!
Any ideas with this one?

[benji]

It should be a relatively easy job to replace the beating on the transfer case side. If you take off the viscous coupling housing you should be able to press on a new bearing in the vc housing (easier than a diff for sure! )

[Hoges]

You do not need to remove the complete transfer case. The front output bearing is part of the casing which houses the viscous coupling unit. You need to remove the front flange and oil seal. You remove the VCU with the VCU housing attached. Then the VCU is pressed out of the housing bearing. The bearing itself is held in place with a circlip. Remove this and then press the bearing out of the housing.

Budget for a "day-long job"...including lunch and coffee and the unexpected! Both shafts need to be dropped from the transfer case. You need to put a jack under the transmission because the cross member has to be removed as well. Once you're into it however it's straightforward. In such a confined space, a 12V electric rattle gun of the type for removing stubborn wheel nuts is invaluable for loosening the central flange nut off the output shaft! Using said rattle gun to give the nut a touch up when re-tightening also helps!

good luck with it!