I have a Land Pride RCR 1872 with about 50 hours of mowing grassy roadsides and woods openings. I noticed a vibration when mowing yesterday and could see the gearbox shaking. I stopped the mower and saw that all four bolts holding the gearbox to the deck were loose. I wouldn't think that should happen and that the bolts would have some kind of locking nut on them. It appears that it will be quite a chore to retighten them. Has anyone experienced this? Any suggestions to keep this from happening again? Thanks for any input.