Copyright Goodheart-Willcox Co., Inc. 575 Chapter 17 ∣ Final Drives 9R tractors and scraper 9R tractors are equipped with the inboard double-reduction planetary final drives. The differ- ential’s side gear delivers power to the first planetary gear set’s sun gear. The ring gear is bolted stationary to the axle housing. The first planetary carrier drives the secondary planetary sun gear. The second planetary ring gear is also stationary, and the second planetary carrier drives the bar axle. See Figure 17-3. Inboard Bull-and-Pinion Gear Final Drives In an inboard bull-and-pinion gear final drive, the pin- ion gear receives its power directly from the differential side gear. Usually, the service brakes are integrated on the pinion gear shaft. The pinion gear drives the large ring gear (bull gear). The center of the bull gear is directly splined to the tractor’s axle shaft, which propels the drive wheel. This type of drive is sometimes used in compact utility tractors. See Figure 17-4. Outboard Single-Reduction Planetary Final Drive On many off-highway machines, outboard planetary final drives are integrated into the axle housing. The final drive is still attached to the axle housing but is located out- board, near the drive wheel. Outboard single-reduction planetary final drives use a single planetary gear set. They are found in both steering drive axles and rigid drive axles. Outboard single-reduction final drives are used in the front drive axle in MFWD agricultural tractors, as well as in drive axles in large construction equipment such as four-wheel- drive wheel loaders, articulated dump trucks, and rigid frame haul trucks. Ring gear A B Inboard axle shaft Planetary carrier Outboard axle shaft Trumpet housing Goodheart-Willcox Publisher Figure 17-2. Two inboard single-reduction final drive assemblies resting on a shipping container. The axle housings resemble a trumpet. Figure 17-1. Inboard single-reduction final drives attach to the differential housing. A—A wheel loader axle with inboard planetary gear sets. The wheels mount to the drive hub flanges. B—A John Deere 8000 series rear axle with inboard planetary final drives. The left side inboard planetary final drive has been removed and inverted in a stored position. The ring gear is bolted to the differential housing and held stationary. The sun gear is machined into the inboard axle shaft, which is driven by the differential’s side gear. The planetary carrier is the output and is attached to an outboard axle shaft. Goodheart-Willcox Publisher Goodheart-Willcox Publisher