Rear Diff Occasional Grind

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26th September 2016, 10:26 AM
Throbbinhood

Rear Diff Occasional Grind

Ok, so, weird one. GQ LWB rb30 4.3 diffs on 35's.

I've only had this happen twice. Once when flexing in mud, and once when driving up a hill covered in ice.

Basically, every now and then in these extreme low grip situations, I'll get a grinding noise and then sudden drive from the rear.

I haven't dumped the oil. At a guess, I'd say that I'm lifting a wheel or there is insufficient traction for the LSD, and it's basically turning itself into a single pegger. When the lifted wheel drops back down, or I get a bit of traction, I get the grind which I think is perhaps the clutch packs in the LSD grabbing again?

Has anyone experienced this? Any thoughts? Diff/car has only done 130k kms, and normally LSD's fine (like I said it's only happened twice).
26th September 2016, 11:51 AM
mudski

Changing the oil would be the first thing I would do. You could have water in the oil which would be damaging the diff.
26th September 2016, 04:48 PM
dom14

Check the diff breather to make sure it's not blocked with mud or water might have gotten into it through the breather.
Assuming you haven't done it already, extend both front and back diff breathers to a higher spot with a hose and a filter.

Yeah, the noise sounds like LSD clutch pack engaging/disengaging.
Check to make sure the pinion & uni has no play.
26th September 2016, 05:19 PM
Throbbinhood

Quote:

Originally Posted by mudski

Changing the oil would be the first thing I would do. You could have water in the oil which would be damaging the diff.

Yeah, I know. I've just been lazy haha, hoping there might be an answer here. What diff oil would you recommend, and any idea how much I need?
26th September 2016, 05:20 PM
Throbbinhood

Quote:

Originally Posted by dom14

Check the diff breather to make sure it's not blocked with mud or water might have gotten into it through the breather.
Assuming you haven't done it already, extend both front and back diff breathers to a higher spot with a hose and a filter.

Yeah, the noise sounds like LSD clutch pack engaging/disengaging.
Check to make sure the pinion & uni has no play.

They are already extended, but I'll get back under and double check I haven't ripped a line out on a branch or something.

Thanks for the tip on pinion and uni, I'll check it out.
26th September 2016, 05:40 PM
mudski

Quote:

Originally Posted by Throbbinhood

Yeah, I know. I've just been lazy haha, hoping there might be an answer here. What diff oil would you recommend, and any idea how much I need?

LSX 85/140 and according to Castrol is needs 2.1ltrs.
26th September 2016, 05:57 PM
dom14

Quote:

Originally Posted by Throbbinhood

Yeah, I know. I've just been lazy haha, hoping there might be an answer here. What diff oil would you recommend, and any idea how much I need?

The one that is recommended in the manual is LSD oil. When you give vehicle model and year, Burson, Supercheap, etc know the exact oil.
You'll need a four litre can for the rear diff, but won't need all of it.
I used Nulon LSD oil, 4 litre can. Just looked in the garage to find it, couldn't find it.
There is a thread somewhere about using a 50/50 mixture of engine oil/diesel to clean the LSD.
Google it, it should be somewhere in this forum or the other forum, but I don't think you have to do that.
For the factory front open diff, it's normal gear oi(SAE 80-90).

If you're buying both oils keep them separate. It's too easy to accidentally mix them up.(I did and had to drain and clean the whole diff :1087:)
Also use separate funnels(or wipe before use).

I put the rear wheels on ramp and use a piece of garden hose attached to a funnel to fill the diff with oil. Tie up the funnel+hose to the spare wheel. It's a far better method than using the $20 hand pump, which is a real PITA to use. Or you can build below cheap unit with an air pump.

http://www.nissanpatrol.com.au/forum...-service-video

I made my own removal keys for diff and gearbox drain/filling plugs using 10mm-14mm bolts from Bunnings. You just cut them short and file the end to get the square key shape. You only need two keys for diff and gearbox plugs. It's fairly quick job with an angle grinder and a hand file, or if you're good with the angle grinder, you won't need the hand file.
26th September 2016, 06:54 PM
Col.T

G'day Dom,
what a simple, brilliant pump on that backyard man's post.
BTW I thought the standard 1/2" driver end was all you need for the plugs. Still, whatever,
regards,
Col
26th September 2016, 07:10 PM
dom14

Quote:

Originally Posted by Col.T

G'day Dom,
what a simple, brilliant pump on that backyard man's post.
BTW I thought the standard 1/2" driver end was all you need for the plugs. Still, whatever,
regards,
Col

Thanx mate.
Yeah, I remember trying to use 1/2" driver without much success. It didn't either go in or was too loose.
There are two different square allen key sizes for gearbox & diff drain/fill plugs.
I wasn't able to use 1/2" driver for either one of them, so I ended up fabricating my own, which wasn't hard at all.
Trip to Bunnings cost me more time than making the too keys. :)
I can only speak for my RB30 Patrol though, but I believe it should be the same key sizes in all GQs.
27th September 2016, 12:08 AM
dom14

Quote:

Originally Posted by dom14

Thanx mate.
Yeah, I remember trying to use 1/2" driver without much success. It didn't either go in or was too loose.
There are two different square allen key sizes for gearbox & diff drain/fill plugs.
I wasn't able to use 1/2" driver for either one of them, so I ended up fabricating my own, which wasn't hard at all.
Trip to Bunnings cost me more time than making the too keys. :)
I can only speak for my RB30 Patrol though, but I believe it should be the same key sizes in all GQs.

When I said, I "believe" doesn't necessarily mean I'm right though. :biggrin: :icon_bonk::cheers: