[willisodhiambo]

A friend is looking for a replacement gearbox for an X6 M54 engine. The gearbox in the car is 6hp28 but realoem shows it should be 6hp19z for his chassis.

Can any be used or it should be exact? What is the difference between 6Hp19, 24 and 28? I guess the HP rating?

Current gearbox goes into limp mode when car is driven hard. I think it was replaced and may be wrong version for the car?

[aleksandrw]

i think he should try changing oil and filter first , as on hard driving a clutch is slipping.if the oil change is not solving the problem, mechatronik should be check as after 100k valve pistons wear. as for a second hand gearbox that you dont know nothing about , could do the same soon or a later .as the production of n55 begin in 2009 i dont think they use hp19 . i think(dont know for sure) 19 was used till 2006( at lest on e60 )

[willisodhiambo]

i think he should try changing oil and filter first , as on hard driving a clutch is slipping.if the oil change is not solving the problem, mechatronik should be check  as after 100k valve pistons wear. as for a second hand gearbox that you dont know nothing about , could do the same soon or a later .as the production of n55 begin in 2009 i dont think they use hp19 . i think(dont know for sure) 19 was used till 2006( at lest on e60 )

You are right. My mistake. It is M54. Oil and filter already changed, mechatronic replaced once already. A rebuild would be best but no trusted specialist in Kenya. For that reason a used unit best. If used unit develops fault then a rebuild of it can be considered.