yeah more than likely the pinion bearing is shot. still drives but causes pinion and driveshaft to wobble. pulling the diff off is only way to know for sure. when you get it off grab where driveshaft goes (pinion) it should spin but be nice and tight, no wobble side to side.
don't ride it that way or you will tear up pinion/ring gear. I rebuild them if your interested pm me
Trikes: All Honda: 84 250r, 85 86 and 87 250sx, 84 and 85 125m, 79 82 84 and 85 110's, 73 us 90 and 77 atc90, 75 atc70
Cycles: Honda: 71 cb100, 78 cb750 coming soon cb750 trike. Yamaha: 67 yds 3 (250cc, 2cyl, 2 stroke), 82 750 SECA
Other toys: Chenoweth VW sandrail dune buggy, old race go kart, racing mower, 76 Arctic Cat Pantera 440 snowmobile
KEEP IT ON ALL 3 OR AT LEAST 2 AT A TIME