Just bought vehicle. It makes a roar similar to large tire roar, but not sure that it'* not the front end. It sounds too metallic/gear-like. It sounds like it'* coming from the front.

What are some particular things I should check?

Does it seem to roar in tune with the RPM of the engine?

No, it roars in tune with the speed/rotation of the tires/wheels, but not in tune with the RPM of the motor.

Could be a wheel bearing. Can you get the front wheels off the ground so you can check for play in the bearings?

Jack each corner of the vehicle up and push/pull on each wheel to see if there is any looseness indicating a bad bearing. Could also be a CV joint on the prop shaft, or a problem in the differential. jwfirebird is pretty knowledgeable on trucks and is on every day. We should hear something from him shortly on this.

Thanks for the input so far. Will try that out and watch for a reply from jwfirebird.

the likelihood of any 4wd failure like that is much less likely than the bearings or tires but they sound the same and most times the bearings wont be bad enough to cause play. i would rotate the tires see if the sound moves. bearings normally will get louder or softer when turning. tires usually wear out even side to side so turning wont normally change the sound