The problem is not the regulator, because the regulator works fine without the window attached to it, and the window glass has a lot of resistance to being manually pushed up and down even when the regulator is not attached. It is as if the weather stripping has too much friction against the glass.
My window was recently reglued to the regulator strips because they came off the window when I started to roll it down when there was ice frozen around the window. The window rolled up and down hard prior to that happening too.
In any event, when the body man was looking at it prior to regluing it, he wondered why the window was so hard to manually push up or down. I asked if maybe some lubricant could be used on the weather stripping, and he said no, it would make it worse because it damages the weather stripping or something.
However, there is this post from a forum:
OK to properly grease the rubber tracks that the windows ride in, you need to go to a parts place and pick up a can on "3M DRY silicon spray lubricant" Make sure it is the dry type. do not use white lithium either, because it is bad for the rubber. That is a common problem with just about every car with power or manual windows. the rubber drys out and it takes so much effort to move the window that sometimes the motor can't move it. Try the spray first before tearing everything apart and replacing stuff. Just roll the window down and use the straw to spray down the channels of the tracks. Then roll the window up and down a few times. Repeat if needed. Doing this once every 6 months- 1 year will help keep the rubber in good shape.
He acknowledges that some lubricants can damage the rubber like the body man said, but he says that 3M dry silicone spray is fine (I happen to already have a can of that exact stuff, I use it on some of my arcade machine joysticks).
So does anyone here know if 3M dry silicone spray is okay to use, and if not, is there any other solution apart from maybe buying new weather stripping?