Freelander transmission vibration

There is a significant vibration which appears to come from the transmission on my 1998, 70,000 mile Freelander TD. The vibration is most noticable
between 1600 rpm and 1900 rpm in 4th and 5th gears when there is a slight load on the engine such as acceleration or climbing . The vibration begins above the speed where labouring of the engine ceases if the car is gently accelerating. In other words during gentle acceleration in a high gear just above the point where the engine is no longer labouring, there is a smooth rev band for about 200-300 rpm before the vibration starts at 1600 rpm. I can of course avoid accelerating in high gears in the troublesome band and there is no vibration problem, but in normal gentle low speed driving the vibration band is exactly at the point where the engine is comfortably ready for the next gear change, which drops the revs right back into the vibration band again, so it is very irritating.
The vibration is greatly increased with more load on the engine (and has the appearance of a labouring engine) such as when accelerating harder, or climbing a gentle hill. Strangely however, if the handgrake is applied against power and the revs maintained in the vibration band, the vibration ceases immediatelly - until the brake is released when the vibration returns again. The brake seems to have a damping effect on the vibration despite the fact that it is creating an increased load on the engine which tends to suggest that the cause is not labouring of the engine, but a harmonic vibration from some other source within the transmission. The local Land Rover garage did not come up with an adequate explaination for the problem. Anyone have a clue?
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Eric Hi,
this reminds me of the problem a fellow member of the LR club of Greece had some time ago.
It turned out that it was a damaged vibration dumper (the black round thing sitting in front of the viscous coupling unit)
Hope this helps.
Take care Pantelis
P.S. those dumpers are available as a spare part.

transmission
begins
just
ready
vibration
the
returns
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problem.
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