Series III 2WD Vibration

My 109 has suddenly started to judder/vibrate in 2WD. Seems like its the front end and its an up/down motion, not side to side if that makes sense. Like driving over lots of small ridges. Lift off the gas and it smooths out.

Put it into 4WD and everything is smooth again - no vibes at all. Any idea where I should start looking? Propshaft, halfshafts or hubs?

(Its got standard hubs BTW)

Anyone?

Have you had a new diff fitted recently?

Strange
I cant think of anything that would cause that on a series.
Are you shure you have your knobs set right ie?
Yellow knob up and red forward = 2 wheel high ratio (Rear drive only)
Red forward yellow down = 4 wheel high ratio (front and rear wheels driven)
red knob back yellow knoub up = 4 wheel low ratio (front and rear wheels driven)

I would jack the front up and check out the uj's / diff.

The reason i asked about a diff is that like clivees above suspects, you could be experiencing wind up in transmission. I had a series once and the front diff blew, fitted another not realising that the previous one was from a rover p4 or something like that and was quite rare. After using 4wd it would stay in 4wd as it was 'wound up' and start to 'skip' as i was driving until the tension had been released from the transmission. basically two different diff meant two axles turning at two different speeds, no wonder it was struggling climbing slopes on the first outing after having it fitted!

sounds like U.Js not that im a landy expert but in the days of rear wheel drive lots of vibration usually came just before the prop shaft fell off why not remove the front prop take it for a drive and see if the vibration stops if it does replace the U.Js and put it back on

With front wheels off the ground there's a lot of play in the front propshaft - but the UJ's feel OK, AFAIK its the original diff (but a bit leaky)

When turning the propshaft by hand in gear and 4WD should there be any play? I should have thought it would'nt move at all. I'll compare it with the back when it stops raining!

Nope, its not the front propshaft - I removed it, drove it a short way and the vibrations are still there. So its got to be the diff/halfshafts/hubs

Solved. Removed rear propshaft - UJs are knackered. Drove it on front wheel drive and no vibes at all, so looking less expensive!

It certainly sounds like U/J's on the front axle, maybe even wear in the front diff. When the front end of the transmission has nothing to do but rotate by the drive of the wheels all sorts of wear can show up as vibration, especially at speed, which of course is alleviated when 4wd is selected and drive through the front shafts keeps it all nice and tight, but that will wear out tyres on road quickly. Consider free wheeling hubs on front wheels to give transmission a rest. Worst case scenario is the front UJ will fail at speed throwing the front axle -This will definitely cause an up and down movement, but of the whole vehicle and occupants.