Roaring noise from front diff.

Hey guys, I recently (last month) bought a 1997 Jeep Cherokee Sport 4x4 for cheap. Guy needed money and it seemed like a solid deal. It has 212,000 original miles on it and the guy has owned it since 2007. His daughter drove it back and forth to school. I noticed the Jeep had a grinding/roaring noise coming from the driver's side front which I thought was something to do with the brakes. Replaced the pads and rotors and checked the caliper to see if it was sticking, it wasn't.

I then decided to crack open the diff and let the fluid drain out. I sprayed the gears off with brake clean and checked them out. I didn't notice any huge chunks taken out of the ring and pinion/spider gears and everything looked decent. The fluid was pretty shiny when coming out. A little bit of metal shavings on the magnetic drain plug. I replaced with 75w140 Mobil 1 synthetic and the noise is still there. It's not near as loud as some driveline noises I've heard from previous Jeep's but it still worries me. My question is...what are the chances it's just going to blow apart on me? I plan on driving the Jeep to the mountains an hour away from my house a lot this fall/winter and don't want to be left stranded. It's very mechanically solid aside from this issue.

Was the fluid level correct or was it low? Frequently on the high pinion model D30's if they develop an axle seal leak, the fluid level will drain down low enough to allow the pinion bearings to basically run dry.

Also the unit bearings on the front are a common source of grinding/roaring noise, did you check them out?

Good axles don't drain shiny. On mine the gear oil comes out like it went in, like honey. If acceleration and deceleration don't affect it, its probably the carrier (side) bearings. They can make noise for thousands of miles and still keep on going. However, depending on how loose they are, you can actually trash the axle housing by letting them run like this. As the cups move about without preload, everything is moving and wearing and at some point new carrier bearing cups won't fit properly in the housing. Axle shaft seals will wear and leak, gear set will get worn, etc, etc, etc.