My driver's door window has a bit of a grind to it that I've put off addressing for a couple of years now...raising or lowering works fine, no perceived "slowing" in speed, just sounds like there are rocks in the track when it is in motion. Thoughts on whether or not this is a regulator issue or a motor issue?

 

Mine can make some nasty sounds too from time to time. Especially if my car is in serious need of a wash.

 

Mine's definitely not dirt-related, noise happens internally regardless of how clean the window is.

 

i used wd 40 on both sides of the window track while window is down and repeat once so often . it helps making the window rising and lowering with lesser grinding,,try it ,,got nothing to lose

 

I used a silicone lubricant, didn't make any noticeable difference.