The big news, however, is down in the engine room, where a redesigned drivetrain has brought six speeds, a lighter clutch and a new engine/transmission interface. Peak clutch effort was reduced by a third with a new ball-and-ramp mechanism mated to a redesigned diaphragm spring. The new gearbox features a redesigned shifting mechanism that uses sliding "dog rings" instead of heavier moving gears, and beefier helical gears instead of the old unit's smaller straight-cut gear pairs. The primary ratio is taller, and the new gear ratios provide taller overall gearing in the new sixth gear than the old fifth gear, reducing engine speeds on the highway. The new tranny also gets beefed up with bigger bearings, improved seals and a stiffer housing that dispenses with external oil lines. The new primary-drive housing comes with an automatic chain tensioner, eliminating adjustments and the related inspection cover. All these improvements were supposed to offer greater durability and increased load-carrying capacity, but something didn't work out as planned because there is currently a service bulletin calling for owners to have a primary-drive bearing replaced every 15,000 miles. Harley has really stepped up in the matter and will pay not only for all the parts and labor, but also to have the bike taken to the dealer. Some owners see this as a nuisance, but others regard it as a free primary-drive service and an opportunity to get the bike to the dealer for regular service, as well.