my 2018 u`force 800 with 83 miles on it developed a massive [ in my estimation ] oil leak out of rear driveshaft output shaft.. I was able to stop leak by tightening the 15 mm head bolt in the center of the driveshaft yoke.. I had to bend the box end of a wrench to get on the bolt.. So far its good. While i had it in the shop on a lift i remover the drive belt cover to check belt for debris.. Seems in the fall chipmunks were busy storing acorns  in there.. Installed a screen over open air exhaust/intake tube. End oif problem i hope

I'm having the same oil leak issue out the seal for the rear driveshaft where it leaves the engine.  Problem is I cant find a good way to get to the bolt.  From below there is a cross-member in the way.  I removed the bed and can get a box end over the bolt head but no room to tighten it.  Any ideas?  Why does this bolt come loose in the first place? 

A couple of things come to mind. (my opinion)
1. Factory is not torquing to spec.
Why? Torque wrenches, especially assembly line wrenches need to be checked periodically and re-calibrated if necessary.
Why? Assembly line does not use a torque wrench.
2. This might indicate it to be a good idea to do around and verify every single nut/bolt on these machines with a torque wrench and torque all to spec.
Beings I have 15 minutes of run time on my 2021 Zforce 800 Trail, I think I will do this straight away!

I recently found that bolt laying loose in my under skid panel. I went to my local dealer and he said this was a known problem. I let them put it back in as I did not have a good way to get under it to try for myself. They found that the seal was bad. Replaced the seal and added Loctite to the bolt when they put it back in ... $173 They said it took them all afternoon because the also took the shaft out to replace the seal.