[TedG]

Put your bike on stand and check the rear wheel for side to side play like you would check the bearings on your car wheel.
I just had a scare, I did mine and it moved quite a bit. I am thinking bearings, hub and axle. Looked up the price and it is about $1000.00 to replace that stuff.
Found out is was the nut holding the rear hub had come loose.
Luckily I caught it before and damage.
Just an FYI.

 

[H2015]

There has been a previous thread on this, the nut on the right hand side of the wheel/axle, can't remember who posted first but they had to replace the parts you mentioned I think, until someone noticed it was that nut coming loose.

I check mine now as I came across it being slightly loose some time ago after reading about it. It's not an obvious place to check so can get overlooked.

Good job you found it now, especially with the amount of miles you do!

Cheers,
Don.