Hello Jim, I will see if I can be of some assistance.
On the Jd 450B dozer, you will have to split the track and remove the final drive to gain access to the steering clutch components as well as the brake band. Also, under the seat, you will want to remove the small inspection/adjustment cover and verify all the linkages are intact BEFORE you go though the trouble of removing the final drive. I don't recall if the 450B uses a wet clutch or a dry clutch(pretty sure it uses a dry clutch), I know the 350's (the lil brother of the 450) use a dry clutch/brake until the C model. If it is a Dry clutch, its quite possible the clutch steels have rusted and made the clutch "pack" grow to the point the pressure plate can't disengage the clutch. No amount of adjustment would fix this problem, again, the final would have to be removed to gain acces to and make repairs/cleaning as necessary. The brake/clutch components will come out with the final drive, you may have to back off the brake band to allow the drum to slide out freely depending on the amount of wear the drum has (a ridge forms, can hang up on the brake band, the band stays in the housing). I hope this information is helpful.