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I have the ubiquitous clunk.... and I've been trying to find it.

The clunk occurs when I release the clutch suddenly - or with the clutch held in, if I jab the brakes. I can (most of the time) drive so it doesn't occur, but that's like having an ugly wife and getting round the situation by not making eye contact....

One additional point is that I can't seem to cause the clunk in reverse.

I recognise that this could be anywhere in the transmission line, so from what I have read: drive flanges, half shaft, diffs, prop UJ's, prop slider joint, transfer box, transfer box diff, gear box, A-frame ball joint, radius arm bushes.

The A-frame ball joint is ruled out as I've recently replaced that.

Currently I am laid low with a bout of the flu so haven't got much further, so if someone would be kind enough to makes some suggestions and give an opinion, I'd be hugely grateful!

One thing I did do before the flu, badly, was attach a video camera underneath* pointing at the front diff, the front prop gearbox end, the rear prop gearbox end, and the rear diff. Sadly - I didn't set the camera up properly and almost everything is totally black.

I have managed to fiddle with contrast to get a little bit of picture, and when I'm back to health will repeat the experiment.

This is the rear diff - and sadly its the best quality!!

The clunk is quieter here and there's no movement in the prop (which leads me to think the problem is the front - when you see the next clip). I guess removing the front prop 'might' help confirm this.

This dreadful clip is the gearbox end of the front prop played at half speed - the sole bit of paleness on the screen is the prop - you'll see it start to turn at about 30 seconds. Here the clunk was louder and (at this speed) you can see a small jump in the prop...

So any opinions on what to check?

I've had a screwdriver in the UJ's and haven't been able to create any movement - though I'm new to looking for play in UJ's .... I've also tried prying all of the suspension bushes and found no play.

Its a 2000 Td5 with just over 60K - so I wouldn't expect diffs or gearboxes?

One thing I did wonder is, I have poly bushes on the chassis end of the radius arms (its 3 linked) and I did read somewhere that someone had done this up hugely tight and stopped a clunk - I could imagine that if it were these that would account for why I can't cause it to happen in reverse.

I've had a good look over all of the 3 link bushes at the front and can't find any play - though I may just need educating ...

So any help and suggestions gratefully received !

* it may have been attaching the camera underneath in the freezing weather that contributed to the onset of flu ..

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Perhaps if I take the front prop off I can check the sliding joint isn't seized , or a UJ, and run it in diff-lock to see if the clunk has gone...

I presume that as I brake, or suddenly unload the transmission, the front suspension compresses - and if the prop is seized somewhere it causes a jump like to one in the clip... ? Does that sound plausible?

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Worth bearing in mind, I have found that running in diff-lock with a prop removed is very very clunky! I assume it's due to the slop in the centre diff, but whenever I've run with just one it's been awful :huh:

Might be that I have a semi-knackered LT230 though....

Makes it hard to diagnose the source of a clunk :P

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Thanks James! When I get to try it out I'll post back on how noisy it was. I'm hoping that when the prop comes off it become apparent that the slider, or part of a UJ, is seized.

Does anyone know what the torque is for the chassis ends of the Radius Arms?

I still think the fact I can't replicate it in reverse should narrow it down .....

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  • 2 weeks later...

Thanks Kyle (DDO173) - I'll just ensure they are compressed a bit and not loose when it thaws out there.

LandyAndy - I presume you mean slack in the diff flange and pinion? - I'll try and test that when the front prop is off so I can give it a good wriggle around.

I don't know if its through listening too much - but I'm beginning to think I can hear a bit of rumble that wasn't there before....

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  • 1 month later...

A small update:

I removed the front prop and ..... its fine huh.gif So - i popped it into diff lock and went for a drive and my clunk is still there .... I'm now leaning to it being at the front of the rear prop.

Whilst the prop was off I took a moment to check for play in the front diff flange:

Which I believe is very good, with only a small amount of movement? There was no play in any other plane.

I also stuck the box in gear and tried the front transfer output flange:

Which again, I believe is very good ? I was told to expect a dreadful amount of back lash with the front prop removed but it was actually pretty good to drive...

So the search continues.

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Incidentally - I think I have figured out what the small jump in the front prop is ...

I am at standard height but have the +2" turrets - so I have more compression travel on the suspension. I think that when I stab the brakes the extra travel means the prop slide joint is no longer able to absorb the movement and so jumps a little as the UJ flexes to absorb the movement.

I'll look into addressing that by perhaps having a prop altered to put the slider joint a little more open when in the neutral position.

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  • 3 months later...

Found it !

....and surprisingly it was the spring plates on both sides of the front axle being loose ....

There was no play to be felt by hand, but all four bolts were all quite loose when checked with a spanner.

The symptoms was a loud clunk/thunk that from inside: sounded like it was from around the transfer box - and from outside: a noise that was hard to trace except to say that it sounded like it was above the front diff. It clunked when coming off the power when going forwards - and when sharply applying power in reverse.

I'm amazed such a loud 'thunk' could be generated by something so innocuous.

...... [sigh] what a relief to get rid of it.

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