By: news (offline) Monday, 05 June 2017 @ 10:10 AM ICT
The differential problem was probably the collapse of the big bearing on the crown wheel which, when compared with the ABS situation, isn’t such an expensive deal.
With the BMW R1150RT and other motorcycles most problems can be fixed with a proper workshop / repair manual. Some faults can be fixed without having to replace the whole system. If your friend hasn’t had a proper diagnosis from an authorized BMW dealer, he should.