I recently noticed a moderate whine while driving my 2001 Chevy Impala (100k miles) on the highway. I thought it was an engine bearing until I realized that it changed in pitch and volume as power changed, but not rpm per se. That is, as I accelerated or went up a hill, it got more pronounced, but went away when coasting, even if I put it in nuetral and revved it. Also, I discovered that if I put the shift column in '3' (forcing it into 3rd -- it is a 4 spd tranny, right?), it never whined?
So I'm concluding that it is the transmission, but I have no idea what the problem is, or what I can do about it. The tranny fluid is full, but I've never changed it or the filter. I'll start there, but need help to really figure this out.
What do you think