Concern for the rear drive

I finally checked the rear brake. It seems like there is braking action and it seems to release. Which means that the sluggish rear wheel is something else. I've changed the final drive oil, that shouldn't be the problem. On the 76 there is a grease fitting where the shaft meets the final drive. I did some research on that; the general concensus is that the fitting is useless. The rear wheel should be removed, the splines should be cleaned and replaced with Moly 60. Theoretically, grease through the fitting should do the job, but most people of the forums said it was useless and was removed on later bikes.