My truck whines in 1-3 gear and the closest thing i can relate it to would be a m22 rockcrusher, just a little more quiet. It only does it when there is a load on the transmission, whether it be me accelerating or decelerating in gear. I was reading a thread on here saying that a bad pocket bearing in the transmission could be to blame? Its been doing this for as long as i can remember, even back when the original owner had it. I just changed the transmission fluid and it's the same. I really like the sound, doesn't bother me at all and the trans shifts fine, i was just wondering if this needed to be addressed or is nothing to worry about.

__________________
1993 Ford Ranger XL, M5OD-R1 5-speed, 3.0 Vulcan V6, 3.45 open diff, very beat-up, bought for $375.

Is it a scraping noise or a whine?

Mine does it in 1st and 2nd (scrapes). Goes away when car is warmed up.

Just started happening, and I too have changed my transmission fluid recently, in fact I can't help but wonder whether this is responsible.

I'm taking it in to Ford tomorrow for them to look at it. I'll let you know my outcome.