I have one on my 1980's vintage CHNC, and I noticed the air lube system was just not getting enough lube to it. It leaked air horribly as I understand they all do, plus make a lot of noise.
Well the other day I squirted Ballistol lube oil into the front and rear bearing edges of the collet closer while it was turning and it immediately stopped leaking air and it stopped making noise. Quiet as a mouse, and has stayed that way for days of use.
I think one of the problems with the vari-grip is it just does not get lubed adequately with the Hardinge air system.