2000 Ford F150 Transmission problem
 

I currently own a 2000 Ford F150. It has the 5.4L Triton V8 with automatic transmission and rear wheel drive.
Lately i have been noticing a vibration/grinding sound whenever the transmission goes to shift. It isnt affecting the ride of it or the shift feel at all. But the fact that is only happens right before it shifts gears worries me.
I checked the tranny fluid level and thats good. And also the truck only has 67k miles on it and is in great shape.
Any ideas or suggestions as to what this may be?