STRANGE NOISE IN GU PLEASE HELP!!!!!!!!!!!!!!

[mr nismo]

I went down the coast yesterday and noticed at highway speeds a noise that I am quite concerned about.
At 120 full load no noise, no throttle no noise either, but as I just touch the throttle or just as my foot is about to come off the pedal it is making a grinding rumble sound felt and heard through the whole car. If you toy with the throttle you can gt it to do the noise for a while if you get the throttle right but it is only like 2% throttle
It does it in 4th or 5th gear. I have tried 2 tailshafts and its the same with both. I am finding it hard to tell if it is coming from the rear diff or the gearbox or transfer, but I am thinking it is the diff.
Driving round town here it seems fine. It seems to only happen at highway speeds over 100kmh and the faster you go the worse the noise.
Has anyone ever had this or have any ideas where to start looking or how to diagnose this?????????

Cheers
Dan

[gq banger]

It sounds like the center bearing in the gearbox has collapsed or possibly the bearing has spun in the carrier plate. It is fairly common in those gearboxes. But I hope it is something something cheaper for you.

[InSanE]

id say your 5th gear might be stuffed its common on early GU's to strip 5th gear on the main shaft and it will make a rumbling noise when driving and when there bad they make the noise at idle, the early GU box's 5th gear was only half splined on the main shaft witch caused them to strip when 5th is loaded allot from towing. I would recommend getting it to a mechanic so they can run it on a hoist and diagnose the noise for you.

[mr nismo]

I thought it might have something to do with 5th gear but it does the same noise in 4th aswell but you need to be going fast like over 100 kmh.

[gq banger]

id say your 5th gear might be stuffed its common on early GU's to strip 5th gear on the main shaft and it will make a rumbling noise when driving and when there bad they make the noise at idle, the early GU box's 5th gear was only half splined on the main shaft witch caused them to strip when 5th is loaded allot from towing. I would recommend getting it to a mechanic so they can run it on a hoist and diagnose the noise for you.

I thimk mr nismos vehicle is an RD28ti that has the smaller FS5R30A gearbox in it, not the FS5R50B that was fitted to the TD42, TB45, TB48 which had the 5th gear failures

[KIWI]

Are you sure it not related to a lift kit being installed?
My GQ did this, only when feathering the throttle at 100k or so after fitting a lift. This was with gearbox spacers and longer trailing arms.

[mr nismo]

Yes it is the smaller gearbox.

And yes I think this has somthing to do with the lift. I was getting a vibration, and have fitted adjustable upper and lower trailing arms and have corrected the pinion angle. Under load is now perfect, as is coasting, but when just feathering throttle I get this grinding sort of noise, like a dog growling. What the hell is it????????????

[KIWI]

Will just be the uni alignment I would think, just a little fine tuning of the arms, but as it is minor, it may take a while to get right.
Mine improved after regreasing the uni's, but never went away completely

[mr nismo]

I have set the pinion angle using an angle meter and it is spot on. I have snake adjustable arms, with the x-flex bushes they come with. Has anyone had any problems with these? I had vibrations and with the arms now set it has all gone except for this bloody noise

[mr nismo]

I have spoken to a couple of diff and gearbox specialists and they all are saying not the diff or gearbox, but the tailshaft.
Maybe the slip joint.
One thing that has become apparent is the amount my slip joint is pulled out. It is pulled out 60mm, and after looking under other GUs they are only pulled out about 20mm or so. I am thinking this may have something to do with th noise, at high speed it "chattering" as the drive is taking up the slack and releasing the tension, and under load it is holding it still. If the slip joint is only engagd by 20mm or whatever it is would it be able to wobble around? It has a little movement, both up and down and twisting the 2 halves. I have tried 3 different tailshafts and they all do the same thing and all get pulld out 60mm and all have movement and I am guessing its bcause they are pulled out too far.
Could a tailshaft spacer fix my problems???? Is anyone elses shaft pulled out like this?????? And this is on a GU 2.8 LWB with 4" lift

[aussieducker]

Can you try it without the rear shaft in

[roverrat]

Can you try it without the rear shaft in

Thats a top sig line right there .....

[MJP]

The gearbox in my 4.2TD failed (5th gear) but it didn't make any noises like that. Just went bang all of a sudden when i was cruising down the freeway at 100 in 5th. Then had no 5th gear and it was making nasty crunching noises. Presumably the bits that broke! Doesn't sound like your description to me. Could be one to cross off your list.

[j-top paj]

Can you try it without the rear shaft in

[j-top paj]

I have set the pinion angle using an angle meter and it is spot on. I have snake adjustable arms, with the x-flex bushes they come with. Has anyone had any problems with these? I had vibrations and with the arms now set it has all gone except for this bloody noise

i have the same noise when coasting along on the freeway too.
i only got the noise after installing the arms.
do you have top and bottom arms?

i only have the lower ones and i havnt set them correctly.