a little silicone lube on the track and no one sells just the cable. My motor went out on the up side and took my door apart to fix and found that the cabling on mine was mis routed for the upside. I believe thats one reason mine was soo slow going up and it put an excess strain on the motor. I undid the drum and couldn't figure out how to make it work again. I could get it to wind one way but not the other
So I'm replacing the whole regulator here in the next couple weeks.
If you can get some ends put on some cable and you know how to rewind the drum so it works both ways you can go to your local hardware store and make your own cable.