[TR] TR2/3 - gearshift vibration

[Angelo Graham]

Hello List:
Have been getting miles on the '2 in between rain showers this season. 
Have a question about gearbox vibration that can really be felt in the 
gear change lever, especially when backing off the throttle. Usually 
hits around 2000-2500 rpm.
I did rebuild the box, but must admit I didn't pay too much attention to 
the top cover; just changed the 'O' rings on the ends of the shifter 
shafts.
Just wondering if the vibration is 'normal'; I can quiet it down if I 
grasp the lever and somewhat dampen the vibes.
Anything to worry about? Everything seems tight, but can't seem to track 
down what might be causing this one. Don't get it when accelerating or 
driving at a constant speed; just on backing off the throttle.
Thanks again for any insights.
Angelo Graham