hi all, im new to the forum and would really appreciate some help. i ahve a ford focus estate 1.8 diesel 2002 (02 plate).
when i bought the car it needed a gearbox, so got one from the breakers yard and had it fitted. i then noticed a slight grinding noise ( constant regardless of clutch in/out, and gear engeged /not.). took it to NATIONAL TYRES for a diagnosis and they said could be the wheel bearing on drivers side front. had that changed and noise still there, national tyres then said " there was a score mark on the hub when we took it off, but we thought it would be ok. they then reluctantly agreed to change the wheel bearing under warranty if i paid for a new hub. they fitted both this morning, and lo and behold............. the noise is still there !!! they now say it is probably the diff bearing ? what is this diff bearing and how easy is it to change, also is their diagnosis correct ? any assistance on this matter would be very much appreciated, as its a lovely car to drive ( apart from this noise ).

thankyou in anticipation of your help.
ben.