I have a B2 that makes a loud rattling sound in neutral. The drive shifts and operates perfectly. It's gone 100hrs and the oil looks like new, but it rumbles in neutral. The ujoints and gimbal bearing are good. The noise doesn't change when I steer hard over and it goes away completely when I shift into either forward or reverse. Any ideas?

IF you put your hand on the top of the drive as it sits in neutral you can feel the shift fork bouncing up and down as the gears rotate the high and low spots on the bump rings. Put you hand on the drive and have someone shift it in fwd or rev. see if the noise quits. If it does it is just the way they work. First time I heard it I though something was wrong also. But not the case.
Hope that helps.
Dick

Have you greased the Coupler on back of the engine flywheel, I recently had a customer with same noise, he had Never greased the coupler on his nearly new 2 year old boat,
I greased the Coupler and noise was gone,, I did pull the drive and disassemble it and it was perfect internally.

Thanks. I have several drives and this one is particularly noisy. I think this must be what's going on. I do grease the coupler, about every 50 hrs. While I'm at it, what do you think about the drive temp monitors I see around online?

I run 1000gph dedicated drive showers on my Bravo 2,s. Its the best way to keep them cool and make them last longer when used commercially.Good Luck!!!