In my experience on older vehicles the vertical track at the rear (tail light) side of the window gets dried up dingleberries and oxidation encrusted in the track slows the movement and adds resistance to the motor/regulator combination. Secondly, the white lithium grease that keeps the window regulator moving freely in all seasons gets dried up or collects dust and debris causing more friction on moving parts.
My patented two step fix is:
1 - Shoot a liberal amount of WD-40 (not edible) down the rear vertical window track with the window rolled down, incrementally rolling it up and applying more. Let it soak for about five minutes. An almost immediate speed improvement should be noticed.
2 - Remove the door panel and visually inspect the window regulator, it looks like two opposing scissor arms with a gear at the fulcrum (intersection). If the white grease on the gears is dry use the wd-40 and paper towels or clean shop rags to clean the regulator mechanism until dry and free of grease. Buy a spray can of white lithium grease from the auto parts store and apply with gusto being sure to cover all internal moving parts of the window regulator skeleton.
This should also increase the freedom of movement.
Optionally, you could take the time to visually inspect the bottom edge of the window glass which you can conveniently see with the door panel off to observe if there is any play along the bottom edge of the glass where it sits in a tray channel. On some vehicles this may be a shorter seven inch tray with a couple of bolts that go through the glass itself to make a friction sandwich and hold the window in place. If any of this looks weathered or loose remove the glass carefully clean it with a razor knife (if you are trained and certified on such equipment) and apply a generous amount of clear RTV silicone sealant to the place where the glass mates to the regulator. If the window has any side to side play while partially rolled down this needs fixed. Replace the glass, put everything together, check under the floor mats for screws and nuts you may have not reinstalled, shop vac the interior, wipe off all surfaces with antibacterial, pop a deodorizer grenade and run the AC on recirculate ( don’t fart during this process) smack it on the butt and call it done.
Seriously though the vertical rubber/felt window track and dry grease on the regulator are the two common culprits. Your mileage may vary. Safety over everything. Be a bad ass.
