To be fair mines just started juddering slightly in 1st/reverse, when moving off, not noticeable at other times/speeds. I've just done an 02a conversion, using a new sachs vr6 clutch, so I think maybe the 2nd hand flywheel I used may have benefitted from a skim/reface.. I noticed it from the word go with the new box, and have checked everything else over a few times now, so am pretty sure its my fly. It could well be the clutch/fly in your case as well..?