1987 K5 Power Window issues after new Weather Strip Install
 

I have a 1987 K5 Silverado. I'm having issues with all of my power windows since replacing the weather stripping with brand new the old was dry rotted and needed replaced. The windows are now having a hard time going up and down. I now have to help by pulling the windows up and down. They worked fine initially. Was curious to see if anyone has any ideas as to how to fix this issue.

Guessing you mean you replaced the window felts? strip along the channel of the upper door frame and the wipers along the top edge of the door?

What is the condition of your window glass? Is it smooth as glass or does it have wear from the worn out wipers over the years?

One solution is to upgrade the wiring to the window motors giving them more voltage to get the job done. This is a medium level electronic project, you should be able to solder wires and read schematics if you're going to try it out.