Metallic clicking sound when engaging clutch

It's coming from the back right tire when I engage the clutch in first AND when I rev up fast in low gear and then let off all at once (so basically anytime there is heavy torque forward or backward). It sounds like someone hitting on the axle with a ball-ping hammer. I checked the drum brakes, but they don't look like they have any issues. So I have my suspicions:

1. Rear axle U-joint

2. Rear axle bearing

However, wouldn't a bad bearing be whining at higher speeds (no whining present). Anyway, my bet is on the u-joint going out, but IDK.