Got a mystery and looking for thoughts:
My '97 540 w/90K miles, automatic, w/recently replaced cats has a constant habit of rewarding me with a strange soft grinding sound (like water spraying at high pressure on plastic) when applying the gas above 40mph. Very intermittent, but much more audible at the lower 40mph-type speeds.
I swear the sound seems to be coming from the front passenger side, which makes me think wheel bearing, but the sound stops every time I let my foot off the gas, which makes me think transmission(?). It's almost guaranteed to happen more often going up a hill and while making a turn (right) - like on the on ramp to the highway. But it happens straight and level with my foot on the gas, too. And it's now happening almost all the time (60+% of the time)
Any insights or Wild-Ass-Guesses would be more than welcome and much appreciated.