Newbie Question: Grinding noise from hub?

Hey there everyone I'm new to this forum and to the world of Toyotas. I recently purchased (in January) a 2000 Toyota Tacoma, 4 cylinder, 4X4 regular cab, with manual lock out hubs. I ran into my first problem when coming back from my parents house up in Eau Claire, WI down to my house in Madison. I was about 180-190 miles into my trip on Interstate 94 when I started to hear a grinding sound coming from the front left side of the vehicle. I knew it was somewhere near the front wheel. I pulled off the road after I discovered it wasn't going to go away and I did some investigation. I found out that I had accidentally unlocked one hub (the passenger side hub that was making the noise) and left the right side hub locked. Unsure what to do next I locked both hubs and the sound seemed to go away. I figured I'd free them up the next day and see if the noise came back. It did.

Here is what I know so far.

It's not a constant noise.
It seems to kinda start and stop if I hit a bump or I am on a rough road.
If the hubs are locked it stops. but still in 2wd

Sorry for the long post I thought the back story might help narrow it down. What do you guys think? I thought about replacing the problem wheel with my spare and see if that changes anything, that way I will know if its just in the hub or if its something else.

Thanks

 

Sounds like you need to rebuild the hubs, and check your wheel bearings