[FullyZooked]

During the week, I thought I could hear a crunching/grinding noise over the jet like hum and bone rattling shakes from my 31" extremes.

I have taken off the tyres and popped the stockers on for some problem solving. Problem we have is a loud crunching/grinding noise only when coasting(only lightly on accelerator). The noise seems to go on acceleration and deccelaration. There is no shaking or wobbling so that steers me away from the driveshaft unis.

The noise happens in all gears at any speed but severity depends directly on wheels speed.
This leads to to think pinion/crown gear lash? There is a definate slack when taking off. But how much is too much?

The diff has a minispool fitted and backlash was reset to how it was previously. This was done some 8-9 months ago.

I have checked diff oil and she's all sweet. Lever is perfect and no water contamination.

Any ideas? All help appreciated before I start pulling the diff apart!

[FullyZooked]

Noise is hard to pinpoint as it resonates throughout the car. Any chance of a gearbox issue?

I have a bad feeling from the rear diff though. It also feels like the car surges sometimes while accelerating like I've knocked a tooth off the pinion/crown gear? I'll pull the centre tomorrow morning...

Let the thoughts roll in!

[atari4x4]

ever done the uni joints before... sticky/dry uni joint can give that surge feeling.

[FullyZooked]

Yes this is my second tailshaft. When grabbing both sides of the uni there is a small amount of play, maybe a couple of mm.

I have a spare tailshaft I might throw in first before pulling the centre. It's worth a shot anyways.

[Daves4wd]

Is there any play in the piñon when you jiggle it?? Maybe wheel bearings?? Front end is all good??

[shandy92]

FullyZooked wrote:

Problem we have is a loud crunching/grinding noise only when coasting(only lightly on accelerator). The noise seems to go on acceleration and deccelaration.
The noise happens in all gears at any speed but severity depends directly on wheels speed.
This leads to to think pinion/crown gear lash? There is a definate slack when taking off. But how much is too much?

Any ideas? All help appreciated before I start pulling the diff apart!

my guess would be the drive side of the ring/pinion gear, if it was both on acc and dec then that would be different. different parts of the tooth are contacted when accelerating and decelerating. but i could be wrong. i would be pulling it out and checking tooth contact and back lash and bearing preload, couldnt of been done incorrectly.

[FullyZooked]

Yes there is Dave. But your always going to have a small amount of play here, but then the fine line of too much. It's a bit of a tricky one to diagnose. From my experience it's not the sound of a worn or dry bearing but that of a loose mesh or rattling grind sound.

Shandy I have only noticed the problem this week. I'm leaning towards the added load of the minispool, bigger rubber has taken its toll on the ring/crown gear and either worn teeth or somehow opened the lash?! Can that even happen?

[shep]

rear wheel bearings

[shandy92]

FullyZooked wrote:

Yes there is Dave. But your always going to have a small amount of play here, but then the fine line of too much. It's a bit of a tricky one to diagnose. From my experience it's not the sound of a worn or dry bearing but that of a loose mesh or rattling grind sound.

Shandy I have only noticed the problem this week. I'm leaning towards the added load of the minispool, bigger rubber has taken its toll on the ring/crown gear and either worn teeth or somehow opened the lash?! Can that even happen?

not really, as there are locking tabs that stop that, unless a bolt has come loose and made stuff move.....very unlikely. usually ur axles are the 1st thing to notice any added load from lockers and wheels, my splines have a very very slight twist in them because of mine.

check uni's/bearings etc before pulling the diff out tho. but if you put the gear box in neutral and try and rotate the drive shaft how much movement are you getting??? should have a few mm (this is checking ur backlash....i think)

[Daves4wd]

So your piñon isn't leaking a little oil??it's not meant to have any play isn't it?? Mine didn't when I got it. Then I'd be leaning to bearings takes 30 mins to check and while it's out might aswell check your diff for chipped teeth all up it'll take half a day with a mate and if you can't find the problem in the diff then you've got bigger fish to fry if you wernt so far away (over 2 hours) I'd be there helping you out like a bat out of hell

[FullyZooked]

No oil leaking at pinion. The play I'm talking about Dave is lash clearance not sideways movement indicating bearings.

Thanks for the input fellas. I'll swap tailshafts in the morning and work from there.