Yes, the retractor seems to be "strong" enough. I think I have narrowed it down to the little contraption with a "lever" that attaches to the cable. This thing has an the upper and lower shoes resting in notches with this lever in the middle. As the parking brake is applied it pulls the both shoes "in" and "out" i.e spreads the retractor spring thus pushing the shoes out and
in contact with the rotor. This works as desgined.
The problem occurs when the parking break is released...that lever's "elbow" is not popping out completely (hence the thought that the cable may be "sticking" somewhere) thus not allowing the retractor to compress and pull the two shoes together.
I put the old retractor spring back in just to check that the new one for some reason could not maintain tension.
I wish I had a digital camera and that would make it easier to explain.
92 400E 128K
99 GMC YUKON 88K