There are a few things that can be worn, but the most involved would be the bushings, especially the bushing in the sector cover. The GMC shop manual talks about replacing it and align boring it but the Chev manual advises to buy a new cover with the bushing in it. Not all the kits supply the correct bushing for the cover but the proper method is to bore the new bushing using the other bushing and housing for alignment. Also removing the old one is tricky because it is a blind hole.
Brian,
what was wrong with the seal in the kit. I replaced mine so I would like to know if I used an inferior part.
