Window winders?

Hi - I bought my defender the other week and i am very pleased with my new toy! However, one thing i have noticed is that the window winders are very stiff. They wind down ok but winding them up was really hard work. So i decided to take the door card off and remove the winder. I did this and cleared all the muck out of the runners and re lubricated all of the joints, runners and gears. I thought this would free them up and solve my problem. So i re-assembled the door plate and re fitted it with the glass. I then attached the handle and tried winding it up and down but it seemed to go down in jumps of about 2cm and would not wind up. I supported the underside of the window as i wound it up and it went fine! It almost seems that there is too much weight on the arms???:doh:
Does anybody know what is causing them to stop working and are they repairable or do they need new winder units?

Thanks

sounds like new winders are in your future . they may have strained one to many times and broken a few teeth on the gears ..