2000 Chevy Tahoe Window does not go up

The left rear window goes down but only returns up about 3 inches and stops. Motor seems strong untill it stops. Cable seems to move freely until it stops tight (does not seem to be slipping). Does it sound like I need to lubricate the track? Where would you lube (Limited access)? Or does it sound like the whole system needs to be replaced? Dealer says to expect $500+ for repair. I need to find a cheaper solution (DIY?).