The driver's window on my '99 won't go up all the way unless I push it toward the back of the truck and push the power window button with my other hand. I've tried the silicone lube in the channels but it still does this. Wondered if you can adjust the channels or the window itself?

 

sounds like the regulator is worn out...when they wear out they let the window have exccesive play

 

This.
Your regulator is shot. They're normally riveted in, so there is no adjustment. If your interested in getting another one from the junk yard, I'll write it up for ya.

 

How do you now if the JY unit is good or not ?

 

^take a jumper pack and leads...then hook up to the reg and test it

 

I used to take my battery powered drill (18v) and i would strip the leads to the window (after the plug) and power it with the battery. if it rolls up and down strait, your good.

 

Can you not just see if there is excessive play without rolling the window up and down?

 

Not really. all windows move when you push/pull up and down.

 

on mine, the rear guide channel fell off and was lying in the bottom of the door... I haven't fixed it yet, but the little welds broke.