Been looking at my mates '97 300Tdi Disco to do a few fixes, got it all done except for a high frequency vibration between about 95 and 110 kph. He has been down the wheel balance trail, that was of no use, I have removed both tailshafts in turn and checked uni's, rubber coupling etc, running true, balance weights not missing etc, then driven with only the rear shaft in, front shaft out, then vise versa, the rear tailshaft spigot/pilot bush within the rubber "donut" coupling was worn a bit so I rebuilt the pin diameter up and re-machined to a neat fit within the tailshaft bushing which seemed to slightly decrease the vibes but it's still there, checked the exhaust system mounts and cannot see anything that would give this "buzz" at speed, it's definitely a high frequency, (driveline/engine speed).
I'm wondering if it could be an engine mount collapsed, (they all look ok), or the harmonic balancer, anyone with knowledge of similar problems and or possible fixes.

Have a quick check on the radiator cooling fan .. I had a chipped blade (well, about half a blade) causing vibration.

Paul D said:

Have a quick check on the radiator cooling fan

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Thanks, I had the fan off to replace the water pump two days ago and it was in good condition.

Mine had a vibration, mechanic seems to think that the gearbox and transfer box had a slight wobble due to oil seals / gasket failure.

should be getting it back this week so will find out if that was the cause.

Looking at where the tbox and gbox join, it looks like it had been moving about 1mm

LandyMan said:

Looking at where the tbox and gbox join, it looks like it had been moving about 1mm

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Thanks, we can rule that out, I recently had this transfer case out to replace the intermediate shaft "O" rings to stop an oil leak, I know that's not loose.
Like I said, I have been over this Disco with a fine tooth comb and still cannot find the vibe source, giving it back to the owner today to use until I can do some more research.

Tyres new or older?

I had a vibration i couldnt cure until i fitted new special tracks (usually cause vibes not cure them) and after that all was good, do you have a set of wheels and tyres from another landy you could try?

DiscoPol said:

do you have a set of wheels and tyres from another landy you could try?

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Good thought, that thought had occurred to me, but the owner has had the wheels balanced not too long back which he says slightly reduced the vibes but did not eliminate them.
The tyres are fairly old (70% worn), Yokohamas I think, it depends at what speed they are balanced I guess.
I could try the tyres and rims off my beast, they are only a year old and have less than 10,000 klm on them and I know they are running ok on my Disco, might be worth a try.

certainly worth a try if the frequency matches.........
could also be brakes if its wheel rotation frequency

digby said:

could also be brakes if its wheel rotation frequency

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All the brakes were done about1000 klm ago, new pads all round and new rear discs, there are no brake pulsations, in fact they are really good.
The vibes are at a high frequency, i.e. engine or drivetrain rpm, (or so it seems), but I understand that old tyres may go out of shape at speed and develop what may amount to lumps, for now I will follow this avenue of investigation.