My passenger door window started making loud noise when window reached closed position. Then started making it when putting window down. I have left window up afraid it would quit entirely. Now experiencing problem with driver's door also. Anybody experience this?

 

You'll have to do some diagnosis to determine if the motor is failing or the mechanism has problems. Take the cover off the door and have a look inside.

The motors aren't hard to change but be wary of the spring in the regulator, it's easy to pinch your fingers.

As a bonus, if you have to look for used, squarebody Suburban rear door motors are the same however reversed side for side - my 1991 van got a 1986 Suburban drivers side rear door motor in it's passenger front door. Worked fine.

 

Not sure if you already fixed it but I had this on my 95 recently.

The bolts for the motor are covered so I made some cuts to help access them. Was much easier after that

 

I had no problem with this. You take the regulator out to change the motor.