Rumbling Gearbox

I have a 200tdi 90 with about 140k on the clock, which has developed a rumbling sound when backing off the throttle, particularly at motorway type speeds in 4th and 5th. Performance doesn't appear to be particularly affected, but as I suspect it sounds to originate somewhere gearbox-ish I'm a little concerned. Has anyone else had a similar noise? I'm hoping it might be a bearing of some description, rather than the gearbox or transfer box itself? Any help would be greatly appreciated! Thanks!

As a first step, I would get under the wagon and waggle the prop-shafts to check for play in the UJ's.
I thought my gearbox was on the way out for the same reason (although it happened when I backed off in 2nd). There was terrible rumbles and screams.
Upon closer inspection I found the UJ was shot, and the propshaft was grinding it's own bolts off.

Thanks for the advice - I'll have a waggle about! Have recently had both UJ's replaced due to vibrations above 60mph though, so it might not be them. (Either that or there will be strong words to be had at the garage!!) Glad you got yours sorted though - nothing worse than thinking you can hear your transmission tearing itself to bits beneath you!

As you have had the UJ's replaced. Have you checked the sliding joints on the prop shafts? 140k is a lot of distance.

Thanks for that - will have a good look at the prop shafts in general. Any clues on what to look for in the sliding joints - is it just general wear/play etc?

You need to check for rotational movement between the two halves of the sliding joint. You will need to lift a wheel at the end you are checking and release the hand brake, choke the wheels and use axle stands to support the axle, not a jack. If the brake is on and the wheels on the ground you will not be able to turn the prop shaft. Also the weight of the vehicle acting against the hand brake will take all the slack out of the transmission. This can hide the problem, as when you check the shaft nothing will be able to move so it will all seem O.K. Try and twist each half of the prop in opposite directions if there is any movement the prop will need to be replaced or repaired. I would start with the rear prop. If it looks suspect you can try removing it, mark the position of the flanges so it goes back in the same place, put the diff lock in and take the vehcile for a short drive and not to fast. If the noise has gone it is the prop shaft. Repeat for the other prop.
Good luck

just as a quick check makesure the garage put the prop back on the right way round and is lined up correctly and check all ujs regards colin

Hi

If you suspect it's a prop shaft check that it's still balanced ! Might seem wierd but if you take a prop off you will find a wieght on it somewhere and just as you have youre wheels balanced youre prop shafts need balancing or they will make some wonderful noises till one decides it's had enough and either bounces down the motorway or shoves itself through you're floor.

Check the wheel bearings and wheel balance because either of these will cause noises, as do tyres.

Charlotte

Thanks everyone for all the replies - have been away with work so haven't checked the site for a while! Sounds like I've got plenty of options to try over the weekend - will let you know how I get on! Thanks again

Stevey

Also check your exhaust pipe... thats what mine was.
Sounds very simple but it was... knocking on the side of the chasis.

when you say play on the sliding joint, should there be no play at all or is a little ok??

There should be no rotational play in the sliding joint.