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Loud Clunk going from D to R


dirtysouthUK
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Hi all,

I have a loud clunk when going from drive to reverse on my auto 3.9V8i Disco 1.

Seems to be coming from pretty much under me, I'm thinking gearbox, but it

otherwise sooooo smooth in all conditions so I'm a bit confused as to what

maybe the cause. Oh and it also does it very occasionally if I accelerate

hard then have to back off suddenly.

Anybody got any ideas? I'm stumped, props etc all fine with no excessive play.

Thanks

Dom

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Depending on the age of the vehicle it could be the mainshaft splines where the mainshaft goes into the gear inside the transfer box, but not on later ones (anything 1996 onwards) how old is yours/what VIN number?

To be honest they all have a fair old clonk going from D to R and back again especially when hot, you probably need somebody that knows the vehicles very well to tell you whether it is normal or serious.

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The splines on the transfer box input gear wear out giving a clonk when changing direction - mine does it, my dad's does it, they all do it. Eventually it will clonk and you'll have no drive :unsure: but a new input gear is £50 from Ashcrofts, cross-drilled to allow better lubrication or you can buy an oil feed plate for about £15 which does a similar job assuming your gear isn't too bad. The gear can be changed in-situ.

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The splines on the transfer box input gear wear out giving a clonk when changing direction - mine does it, my dad's does it, they all do it. Eventually it will clonk and you'll have no drive :unsure: but a new input gear is £50 from Ashcrofts, cross-drilled to allow better lubrication or you can buy an oil feed plate for about £15 which does a similar job assuming your gear isn't too bad. The gear can be changed in-situ.

Any after some time in 96 have the drilled gear as std and they don't do it.

On an auto, changing the mainshaft is just a case of taking it off the rear of the gearbox and popping a new one on, not like a manual where a full rebuild is required...

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I like the sound of "change in situ" thats a better prospect than pulling the box out!

It's a jap import of 95/96 vintage, 300tdi shape, very low mileage (genuine). VIN starts

SALL can't remember the rest and don't have it to hand.

I don't think it's serious but I'd like to stop it completely if possible.

Any checks I can do to see if it is indeed the shaft or do I just have to tear into it?

Cheers for the replies

Dom

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Personally im not convinced about the cross drillings being the cure for the oil supply issues, cos how can oil get in to something that is spinning and centrifugal force will throw the oil back out, a chap i used to work with had welded! more than one input gear to the mainshaft to get drive so he could resell the vehicle without a gearbox rebuild, weras the proper feeder plate from Ashcrofts that i fitted to a 200tdi D1 which had well worn cacked up splines fed so much oil that when i stripped it down the spline area was washed vertually clean, it did its job very well and extended the spline life. The feeder went back in with the cross drilled gear and new mainshaft to make sure of the oil supply.

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Personally im not convinced about the cross drillings being the cure for the oil supply issues, cos how can oil get in to something that is spinning and centrifugal force will throw the oil back out, a chap i used to work with had welded! more than one input gear to the mainshaft to get drive so he could resell the vehicle without a gearbox rebuild, weras the proper feeder plate from Ashcrofts that i fitted to a 200tdi D1 which had well worn cacked up splines fed so much oil that when i stripped it down the spline area was washed vertually clean, it did its job very well and extended the spline life. The feeder went back in with the cross drilled gear and new mainshaft to make sure of the oil supply.

I see you point but take it from somebody who has seen many failures of vehicles with solid gears and absolutely no failures with drilled gears in the eleven years LR have been fitting them that it does work, even if it doesn't make sense.

I assume it doesn't need much oil and it is the oil dribbling down through the gear after the vehicle has come to a stop that prevents the problem. It works anyway!

The other thing with the drilled gears is that in most cases the splines are longer than on the old type gear so it spreads the load.

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Ok, allow me to just clarify the advice for myself.

I need to get a drilled input shaft, if this is indeed the cause? And after the advice on here and digging around discoweb etc. etc.

I think your all probably spot on. But after looking at the Ashcroft site it seems I can only fit the drilled type if I have the right

serial number on my box, if not then it must be the drilled plate.

IS this correct? Or can I fit a drilled type in regardless?

Thanks for all the help.

Dom

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I think maybe the drilled gear is only available to replace certain ones, maybe not the "funny" models like MPI? The oil feed plate is just as good as the drilled gear, and cheaper too.

PM "gearboxdave" on here, Dave Ashcroft, I am sure he can elaborate and I would do whatever he suggests ;)

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BogMonster, I think he is "ashtrans". That's how I contacted him recently and he is very helpful.

So it is, sorry. I thought he used to be gearboxdave - but it doesn't show in the display history, dunno maybe my imagination then! :unsure:

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If your transfer box has a suffix 'F' or later it was built with the cross-drilled gear. Mine is a suffix 'E' and I fitted the LR fix, a sort of top hat made of alloy for which they charged me 60 quid. I suppose it is cheaper than a new mainshaft. I read somewhere that if you fit a cross-drilled gear you should remove the thrower plate or whatever. Personally I would keep both, the more the merrier as far as lubrication is concerned.

If I fitted the cross-drilled gear to my rather used transer box at 252 000 kms, would it make the box whine?

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