Most BMW driveline designs use a rubber flex disc to connect the transmission to the driveline. This flex disc absorbs torsional vibrations from the engine/transmission and reduces shock load to the driveshaft and rear axle. The driveshaft is supported by a ball bearing, encased in a soft rubber cushion. This cushion also dampens unwanted driveshaft vibrations, and to some extent both the flex disc and the support cushion can be "tuned" to the specific arrangement of chassis, transmission and rear axle.

The front half of a BMW driveshaft, (excepting early 1600's) is connected to the rear driveshaft with a universal joint and either a fixed or sliding spline. A universal joint is a precision bearing, which allows for small angle changes from engine/transmission movement. BMW driveshafts use an extremely precise design of universal joint with considerable torque carrying capacity for it's size.

The BMW universal joint is quite interesting. Unlike most designs, the roller bearings are contained in a thin shell, stamped from an exotic alloy sheet metal 1 mm thick. It is formed accurately enough to not require subsequent machining and is heat treated sufficiently by the force of the stamping to not require subsequent heat treating. The thinness of this bearing cap allows a large cross and larger roller bearings to be utilized, greatly increasing both strength and bearing life, while keeping size and weight low.

The rear of a BMW driveline (again, excepting early 1600's) uses either another universal joint or a constant velocity joint. They both serve the same purpose, to take up small angle changes, and the constant velocity joint furthermore allows for small length changes in the driveshaft.

BMW driveshafts also utilize an extremely strong tubular section. It is made from a special steel and cold-worked for additional strength, which saves weight compared to other designs of drivelines. The tubing is inertia, or friction welded, to the ends allowing very fast and accurate manufacturing of BMW driveshafts.

Just the type of sophisticated design BMW is noted for!

The problem with this design of universal joint is that repair is difficult, relatively expensive and prone to early failure. Years ago, Driveline Service of Portland, Inc. developed unique tooling and fixtures to correctly repair BMW driveshafts. We created a proprietary universal joint, made to exacting specifications, that specifically eliminates the root cause of early BMW u-joint failure and allows subsequent repairs to be performed inexpensively. It requires extensive tooling, extremely accurate machines and a fundamental understanding of roller bearing theory to properly restore BMW driveshafts. Additionally the employees at Driveline Service of Portland, Inc. that remanufacture BMW and Mercedes driveshafts do nothing else. Very few driveline specialists possess the knowledge, machinery or personnel to properly repair a BMW driveline.

Another interesting feature of the most common BMW driveshaft design is that the front driveline is usually centered directly off the transmission main shaft. This driveline design causes BMW driveshafts to rotate with the smallest amount of radial run-out possible. Additionally the rear part of a BMW driveshaft is centered with the next most accurate means, a precision piloted fit flange.

Driveline Service of Portland Inc. takes advantage of this feature in our remanufactured BMW driveshafts. We created dedicated tooling and balancing equipment that controls the maximum eccentricity error of our balancing within .0076mm. This is literally an order of magnitude better than the typical driveline specialist and is not only within BMW specifications but approaches the limit of commonly available bearings. The extreme accuracy of our processes and the specialization of dedicated employees allows us to warranty our remanufactured BMW drivelines for a longer time than BMW warranties theirs.

In summary, BMW takes great advantage of state of the art techniques and designs in the manufacturing of their driveshafts. Driveline Service of Portland, Inc. with a bit of "Yankee ingenuity", has improved on the serviceability of a great design without any sacrifice in performance. If you would like more information about BMW driveshafts or Driveline Service of Portland's proprietary line of remanufactured driveshafts for BMW automobiles please contact us by any means below.