Join Date: Apr 2002
Location: Dandridge (Near Knoxville), TN, USA
Re: Final Drive
Several years ago I sent my totally failed bearing along with another members bearing which was replaced before it exhibited any real problem to SKF for failure analysis. I posted the results of their report about three times over the years.
Basically, the bearing engineer at SKF said that the major problem most likely stemmed from improper procedures at assembly, and to a much lesser extent a possible machining tolerance issue in that the inner bore showed fretting, which indicated a slightly TOO LOOSE fit of the inner race on the wheel hub.
The major problem was spalling of the races, ON BALL PITCH, which indicated impact/overpressure at assembly causing Brinelling of the races, which over time progresses to spalling. The balls constantly rolling over the spalled areas causes shock loads to the retainer, which then causes it to fail as a result of, not the cause of the bearing failure.
So, I have been totally convinced that the real issue was BMW's assembly procedures, not a design defect.
Remember, this final drive design is several decades old, and the failures did not start showing up in any noticeable quantity until about the year 2000. Most likely due to the larger weight of the LT exacerbating the problem and bringing the failures to the forefront.
Seemingly, LTs after 2005 show a greatly reduced failure rate.
Now, the NEW DESIGN final drives are failing at a pretty high rate, but a different type of failure.
I don't want to achieve immortality through my work...I want to achieve it through not dying.
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.