I had a trans shop put in new bearings a year ago and have had problems ever since with it grinding going into 4th if I shift quickly, but only when the engine is still cold - it goes away once it warms up.

Anyway, I have noticed recently (last few weeks) that when I am driving, if I let off the gas the transmission makes a constant humming (?) noise. So it sounds normal when giving is gas but when I let off and the gears touch on the opposite sides it make the noise.

Any ideas?