Further to Allans excellant post on Hurth
gearboxes I must point out however that some of the smaller Hurth
Gearboxes have a flat
disc type damper plate as shown below which I recently also replaced when renewing my old Hurth HBW-100-2R
box with the new
equivalent ZF10M-2R gearbox
With the disc/polyurathane damper Allans advice to replace it the same time as the gearbox
is sound advice, as if the Polyurathane disc starts cracking then you will have future problems, you will also find a part number 'stamped' on the 'flat part' of the damper when you remove it.
One other fine point is that when fitting a 'new' gearbox the first oil change
should be earlier in accordance with the manufacturers instructions, in my case for example after the first 50 hrs.
As already said replace the damper plate 'whichever type' you have when you replace your gearbox.