I have put some Slick 50 High mileage ATF treatment (thick goo) in my gear case to try to quiet it down but still has this rumbling noise when in neutral with my foot off the clutch and when under power in 2nd and 3rd gear - easy or hard - stays the same - no other gears make noise. Seems to shift fine except about 10% of the time if I quick shift without completely depressing the clutch to the floor it will grind into 2nd or 3rd under full throttle. I have the clutch cable adjusted to put a slight preload on the throwout bearing and it is where I like it. Clutch is a new Centerforce Dual friction pressure plate and disc, new t/o bearing, new pilot bearing, new clutch fork, single hook aluminum quadrant, adjustable cable, Steeda Tri-Ax shifter, good flywheel surface, no contamination, etc... It also is sometimes difficult to put car in 1st gear when at a light when it turns green - clutch on floor & I have to jamb it in.