Constant humming noise
 

Hi all! I have a 2003 Shogun 3.2 DI-d LWB Auto that has a constant humming noise regardless of speed. It sounds like wheel bearing but doesn't get louder or quieter when going around corners as they normally do. There was a lot of metal shavings on the rear diff magnet so mechanic said it's a good chance it's that so I've had it changed but still the same noise. Anyone else had the same issue & know what it could be? Thanks in advance.

Do you have normal road tyres on it?

Yes, normal road tyres. Just taken it out again & I can notice just a slight difference in noise when turning right but only a very very slight deduction in noise?