Main Gear Bearing Design





Johnson Engineering
100 Blake Road
Denver, IA 50622
(319)984-9299 fax

web site map


updated February, 2003

Preventing Main Gear Bearing Failure

High and moderate horsepower applications generate substantial lateral movement of the inner drawn cup bearing, which can eventually work its way out of the main drive gear bore, resulting in catasrophic transmission failure.

A close look at the little details that make a big difference in reliability and capacity.

roller bearing

Our exclusive caged roller bearing is securely retained in the bore by snap rings over washers at both ends. Only Johnson Engineering provides performance details like this.

caged bearing

New SportGear cross section below. Washers between snap rings and bearing shell allow bearing to float freely without axial movement for even longer life.

SG cross section

Snap ring retainers on both ends put an end to bearing "walk" and possibility of failure. Details like this keep your tranny alive and well.

Our bearing can't shift laterally thanks to retainer snap rings over washers. Big and beefy design ends radial crushing.

Caged roller on left, drawn cup needle bearing on right illustrate major differences in load capacity where it counts.

Johnson Engineering's helical main (output) gears replace the inexpensive driven end drawn cup bearing (not shown) with a high performance caged roller (top left) that's capable of much higher load and torque than OE or aftermarket bearings.

We've also added snap rings (top, middle drawing) over washers on both sides of our roller bearing, as well as on the sprocket end needle bearing, to eliminate lateral movement in either direction.

Bearing Size

Premature bearing failure can also occur when the bearing dings the sheet metal drawn cup that retains the OE needle bearings. The small diameter of the needle bearings, coupled with the relatively soft drawn cup sheet metal, allows the drawn cup to become dimpled under heavy loads. And nobody thinks dimples are cute when bearings are the issue.

Our massive caged roller bearing features 3.5 mm diameter heavy duty rollers, over 30% larger and with three times the load capacity of standard 2.5 mm diameter needles. They won't crush down under heavy use, and can't walk because of our exclusive snap ring retainers.

main gear assembly

The entire main gear assembly results in a much stronger gear set. Notice the snap rings on both ends of our stout caged roller bearing on the driven end. Our new SportGear (shown) main gear oil seal is retained by another exclusive, our drive end snap ring that stops unwanted oil leaks that start with a wobbly, unsecured oil seal.

Also check out our four-point bearings for Big Twins and Sportsters!

SportGear™ and TwistGear® are trademarks of Johnson Engineering, Inc. Buell™, Dyna™, and Sportster™ are trademarks of the Harley-Davidson Motor Company. No affiliation with the Harley-Davidson Motor Company is implied or inferred.