130 gearbox grumble?

[Summiitt]

Any ideas on a noise that has just developed on my 03 130 tray top..I have a grumbling noise on the over run/coasting and I whining noise on acceleration, seems worse in the top gears, can't hear it in 1st or second, it is very noticeable with the transfer in neutral and 5th gear selected. 170km on the clock and it's been worked hard for most of them..it's not a diff issue and the transfer case was rebuilt at 40,000km under warrantee..any ideas would be great, cheers

[uninformed]

Sounds like it could be the layshaft bearing. These are known to give problems (not always)

[Summiitt]

Looks like its a 5th gear hard facing issue as a result of a twisted main shaft, not all that uncommon, but still a costly little exercise by the time I throw a new clutch, flywheel, and rear main oil seal..going for an exchange box rather than a rebuild.

[uninformed]

Can you explain more? What causes the main shaft to twist and how does this affect the hard facing?

[Summiitt]

The mechanics who know these boxes backwards tell me it's from lugging away in 5th gear, the shaft gets a torsional vibration which etches the facing off 5th gear, then all the crap goes through the box..he actually said it's more from drivers taking it too easy on the box, he said your better off dropping a gear and getting the revs up, increasing speed and then using 5th, infrequent oil changes are also an issue..I was doing them every 40,000km, he said for a working defender that's loaded it should be at 20,000km due to the heat build up.
Will be about 4k for a reco box, clutch, get rid of the dual mass fly wheel and go back to a conventional one, rear main oil seal and throw a set of shims in the centre diff if it needs them..

[uninformed]

Did they comment on the state of the layshaft and main shaft end bearings?

Im wondering if that torsional vibration is starting because of them?

[TeamFA]

he actually said it's more from drivers taking it too easy on the box, he said your better off dropping a gear and getting the revs up, increasing speed and then using 5th

This is what I do and advocate to others, after having replaced a layshaft. It's an obvious weak point, when you look at the difference in shaft diameter once the layshaft goes into the extension housing for 5th and reverse gears.

Our TD5 is chipped, IC, etc - so makes a bit more power. I suspect that the extra power makes it even easier to leave it in 5th and just put the foot down, instead of changing down to 4th.