Whining in 4th and 5th

Whining, need a little help! Okay so something whining on my 52 TD5. Its only done 48,000 but whines in 4th and 5th. It doesn't whine under power and doesn't whine when I lift off. It will only whine when the throttle is in a position where the RPM matches the road speed so there's no positive or negative pressure on the drive train. I have changed the oil in the gearbox and the oil was clean with no "coppery" residue and the magnetic plug had a very small amount of swarf on it. I am going to be doing the Axles tomorrow as I think it may be an issue with an axle? What could it be, I'de really hate to be replacing a gearbox!!
I don't think its the gearbox as first of all it would whine under power. If it was the bearing on 5th gear then 4th wouldn't whine and if it was the main or lay shaft bearing then 1st 2nd or 3rd would also whine.

paddyred said:

Whining, need a little help! Okay so something whining on my 52 TD5. Its only done 48,000 but whines in 4th and 5th. It doesn't whine under power and doesn't whine when I lift off. It will only whine when the throttle is in a position where the RPM matches the road speed so there's no positive or negative pressure on the drive train. I have changed the oil in the gearbox and the oil was clean with no "coppery" residue and the magnetic plug had a very small amount of swarf on it. I am going to be doing the Axles tomorrow as I think it may be an issue with an axle? What could it be, I'de really hate to be replacing a gearbox!!

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I have a similar-ish problem...although mine is a '93 200tdi with 160k on the clock. Just before overrun but just after lifting off the power, get a short sharp rattle. Only does it once warm?

Nah mine does it whenever. I can hold it on the whine if there's no real resistance on the box. But as you say, when I lift of there's a short sharp whine as it goes from positive to negative pressure

you can rule out axles by removing one prop at a time and go for a driver in diff lock , remove transfer box sump plate and check for end float in intermediate gear , if its endfloat on 5th gear or bearings in gear box it would want a rebuild

Il try changing all the EP90 oils today and go from there. I noticed when I changed the gearbox oil that the level was very high! I took out the filler plug and its chucked it out! Will it do any damage driving in diff lock with only one prop? anything to avoid?

No issue driving in diff lock with one prop removed

Just be aware handling will be a little different