Copyright Goodheart-Willcox Co., Inc. 589 Chapter 17 ∣ Final Drives checked separately from the differential housing because the final drives are sealed separately from the differential housing. Final drives should be inspected for leaks during daily visual walk- around inspections. Some final drives are equipped with a sight glass for checking the fluid level without the need for special tools. See Figure 17-27. Pro Tip Be sure to view the sight glass closely. The glass can become discolored over time, causing a misreading of the final drive’s fluid level. Checking Outboard Planetary Fill Levels On Caterpillar dozers with elevated sprocket undercarriages, several wheel loaders, and haul trucks, the final drive must be oriented in a specific posi- tion before the fill level is checked. The final drive has a horizontal oil level mark across the face of the housing that must be rotated until it is horizon- tal to the ground, with the wording right side up. When the final drive is correctly positioned, the fill plug can be removed. The fluid should be level with the bottom of the fill plug opening. See Figure 17-28. When the final drive oil level line is horizontal to the ground, the drain plug at the bottom of the final drive can be used to drain the oil if needed. Some machines do not have a horizontal oil level mark on the final drive. They have only two plugs, a fill plug and a drain plug. To check the final drive level, orient the final drive so that the drain plug is positioned at the bottom of the final drive. The fill plug can then be removed to check the fluid level. Caterpillar recommends checking the final drive’s fluid level and taking a fluid sample every 250 hours or monthly. The fluid change inter- val is once every 2000 hours or annually. Final Drive Inspection Cover Some late-model Caterpillar dozers (for example a D9T WH) have a final drive inspection cover in the final drive housing. Removing the cover’s four bolts allows a technician to inspect inside the housing to see if any debris has become wrapped around the shaft, potentially causing an oil seal failure. See Figure 17-29. The recommended interval for removing the cover and inspecting the final drive is every 500 hours, or sooner if the dozer is used in severe applications (such as landfills). Tandem Drive Fill Levels Chain tandem drives have their own oil compartment. Periodic fluid level checks are necessary. Motor Grader Chain Drive Fill Levels Caterpillar recommends the following service intervals for motor grader tandem chain drives: • Check the tandem oil level once every 100 hours. • Clean or replace the tandem breather every 500 hours or three months. • Take an oil sample from the tandem housing every 500 hours or three months. • Change the tandem oil every 2000 hours or two years. Goodheart-Willcox Publisher Figure 17-27. This Case IH combine final drive has a sight glass. The final drive has been removed, drained, and inverted. The sight glass and breather are normally located at the top of the final drive. Goodheart-Willcox Publisher Figure 17-28. On several Caterpillar machines, a line on the housing must be horizontal before the fill plug is removed to check the final drive fluid level. Sight glass Fill line Drain plug Fill plug Goodheart-Willcox Publisher Figure 17-29. A drawing of a Caterpillar D9T waste handler dozer’s final drive with an inspection cover that can be removed to check for debris wrapping around the final drive components. Inspection cover