Originally Posted by turb934
Was told by M division engineers that a 1200 mile break in for the rear differentail & manual transmission is more critical than for the engine and then a fluid change.
M division engineers called you in Ontario to discuss trannies and diffs? Ok, I'll play along. I could only imagine that the reasoning would be that IF there were a problem, damage would be minimal ($$) and easily repaired as opposed to damage that takes place under full throttle. By no means though, do gears have a break-in period.