Thread: 2nd opinion on my diff whine

I personally wouldn't blue a second hand banjo style diff when fitting a locker, I'd measure backlash and set it up as it was, unless its obscenely out, obviously setting carrier bearing backlash, but if you put it in the same is it came out, it will be fine, oh, a quick run-out check on the carrier face, prior to crownwheel fitment, or backface of crownwheel is mandatory, altering the existing backlash setting can end up in tears, as you can alter the contact patch, which will take 48298342032km's to remove the non wear patch, it mightn't bust, but will certainly make noise

Originally Posted by Rangier Rover

I wont buy that, It was quiet when it went in, now it isn't.
Even if worn a bit they can be set up OK. just a different tooth contact. If the CWP was knackered they would have noticed I hope

I still think its the diff design/materials at fault here.

From your first post, it only whines under load. Hate to say it, but this CW design flexes under load. What you've done is bolt up a locker to the CW. Normally a good thing, in that it supports the CW. But its altered/lessened the flex under load, therefore different tooth contact to before, however small. That's my guess.

A birdie tells me that the Pumas will have better diffs from Oct VINs onwards. I assume better materials rather than a redesign. At present warranty replacements are the same rubbish diff assembly.

Regards
Max P

couple of suggestions
did they reset pinion height/preload??, pinion height on a P38 can only be set to the bearing face, the common method of measuring to the pinion face 'cannot be used', pinion face is not machined!. So how was the pinion height set.??
If the Trans shop is used to re-building hypoid diffs then it is possible they tried to use the same method on your spiral bevel gear. Set up adjustments are different for the two types!! With a spiral bevel you adjust the backlash to move the pattern from toe to heel, with a hypoid you move the pinion to move the pattern from toe to heel. Can cause confusion!
One of the biggest problems I have found with these P38 diffs is too much pinion pre-load (even from factory), I realise that because of the design with the two bearings close together pre-load is important but too much causes excessive heat build up and premature pinion brg failure.
Hope this helps
Regards Ian Ashcroft

Originally Posted by Ian Ashcroft

couple of suggestions
did they reset pinion height/preload??, pinion height on a P38 can only be set to the bearing face, the common method of measuring to the pinion face 'cannot be used', pinion face is not machined!. So how was the pinion height set.??
If the Trans shop is used to re-building hypoid diffs then it is possible they tried to use the same method on your spiral bevel gear. Set up adjustments are different for the two types!! With a spiral bevel you adjust the backlash to move the pattern from toe to heel, with a hypoid you move the pinion to move the pattern from toe to heel. Can cause confusion!
One of the biggest problems I have found with these P38 diffs is too much pinion pre-load (even from factory), I realise that because of the design with the two bearings close together pre-load is important but too much causes excessive heat build up and premature pinion brg failure.
Hope this helps
Regards Ian Ashcroft

Hopefully they wouldn't have had to touch the pinion height, I am sure you would agree Ian but we never disturb the pinion on any of these when fitting a locker UNLESS high KM, and bearing problems in the first place, which to date hasn't been req.

Do you agree that the Thinner crownwheel and possibly a materials issue is the reason for so many of these diffs having problems in Defenders? I'm certain you guys have seen waayyy more than we have over here.

JC

sorry if i didn't make it clear, its a 05 so its a wolf diff(p38), and its had NO noises be4 the locker,

the shop has told me the only thing it can be is bugged teeth, and nothing they have done, as they haven't touched the pinion in anyway,

the wine is in at 80 and back again at 110 on a cruse , not over-run,

but yes i would of liked if they told me the teath were buggered instead of puting them back in,

when i get back from cruser im going to pull it out and start again, and as to spec in the LR manuals, my mate on this site had the same locker fitted but at arb and his is fine, no wines at all, and heres me thinking a specialist shop would do a better job then accessory fitters arb was cheaper to fit as well,

Originally Posted by stig0000

sorry if i didn't make it clear, its a 05 so its a wolf diff(p38), and its had NO noises be4 the locker,

the shop has told me the only thing it can be is bugged teeth, and nothing they have done, as they haven't touched the pinion in anyway,

the wine is in at 80 and back again at 110 on a cruse , not over-run,

but yes i would of liked if they told me the teath were buggered instead of puting them back in,

when i get back from cruser im going to pull it out and start again, and as to spec in the LR manuals, my mate on this site had the same locker fitted but at arb and his is fine, no wines at all, and heres me thinking a specialist shop would do a better job then accessory fitters arb was cheaper to fit as well,

Your a mechanic, why didn;t you fit it yourself?

Thats the problem with altering the backlash setting on worn gears, that moves the contact patch and can become noisy

If it wasn't noisy before, it shouldn't be now, simple really

Hi JC I agree unless there is a pinion brg issue, leave it alone, the only variable then is the backlash, if replaced as was and it was quiet it should still be quiet. Having said that we still get caught out, sometimes, even using blue there can be problems.
It is not unusual for a 'P38' diff in the back of a 110 to fail, usually teeth strip off the crownwheel
The 'thin' crownwheel is subject to debate, I have never seen a crown wheel split ,yet, not saying they won't, just never seen one. I have seen many with the teeth stripped off.
With regards to matl spec, we did quite a lot of research on materials recently in prep for our new range of C&P. Whilst Rover was better than all aftermarket (including ours) we upgraded our spec to exceed Rover, time only will tell.
I think the Rover P38 diff is just not up to the job in the rear axle of a 110, whether it is , tooth profile, crown wheel thickness, or material spec I really don't know.
We have opted to change tooth profile, thicker teeth, and up the mat'l spec on the new range just launched. Could be we also need to look at a replacement set for the P38??.

Regards Ian Ashcroft