This May Fix Your NP231 if It's "Chirping"

Link to a video on how to stop a chirping noise from your np231. One cause of chirping (there are probably many) can be that one of your bearings is spinning it’s outer race in the aluminum socket/seat. A lot of people will tell you you have to buy a new outer case. Not true. This fix has lasted 2 months with no sign of failing. Note: this video is really for novice diy people like me; I think a lot of people in this group are so accomplished at jeep mechanical fixes that they just need three words: Permatex sleeve retainer - replace the bearings and use this to keep them from spinning. For the rest of us, the how-to section starts at 6:30. The first part of the video is just my awful joking and dad sense of humor so skip it. I hope this helps someone. I didn't see anything like this posted here, but I may have missed it https://www.youtube.com/watch?v=FefYiGUwGSM

Never even heard of this being a issue before !!!!!!!!!!

I've seen seized bearings that spun the outer race or just over heated enough to expand the bore. I've also had crappy chinese bearings that were slightly out of spec. Loctite bearing/sleeve retainer works great if the bearing doesn't fit snugly. Just beware it can make it a bitch to remove during a future rebuild. A few taps to dimple the bore or stake the bearing in is a bit more crude, but also works in a pinch.