What is the Transfer Case Output Shaft Seal all about?

Vehicles equipped with four wheel drive employ a gearcase to switch among two wheel drive, high gear four wheel drive, neutral mode, and low gear four wheel drive. This gearcase is known as a transfer case. It uses a chain drive and gear reductions inside in order to transfer power from the transmission to the rear differential and the front differential according to the driver’s input. The chain and gears rotate in fluid that lubricates and cools the components inside the transfer case, and seals keep the fluid from leaking out past the input shaft from the transmission and the front and rear output shaft to the differentials. When one or more of these seals leak, fluid not only gets on the undercarriage and ground, but the transfer case is no longer able to effectively cool and lubricate the internal components. If the internal components overheat and seize up, or a catastrophic failure occurs to the transfer case, the four wheel drive system will not operate.

Keep in mind:

• The transfer case does not have a fluid level indicator or dipstick. Any fluid leaks should be addressed immediately to prevent internal damage from low fluid.
• Seals such as the transfer case output shaft seal will normally sweat due to the output shaft rotation.

How it's done:

• The vehicle is lifted and supported on jack stands
• The driveline is removed and transfer case output yoke is removed
• The defective transfer case output seal is removed and replaced with a new seal
• The transfer case yoke and driveshaft is reinstalled and the vehicle is taken off the jack stands
• The repair is verified and the vehicle is road tested for proper operation

Our recommendation:

The transfer case is not made for any routine maintenance, however, if the transfer case fluid is leaking from either the front or rear seal, one of our expert mechanics needs to remove and replace the seal to prevent damage inside the transfer case.

What common symptoms indicate you may need to replace the Transfer Case Output Shaft Seal?

• Brownish color fluid spots on the ground under the middle of your vehicle
• Whining noise when shifting transfer case modes
• Grinding noise from under the middle of your vehicle while driving
• Rattling noise when driving at highway speeds
• Transfer case will not shift between two wheel drive and four wheel drive modes

How important is this service?

If your vehicle is equipped with four wheel drive, the transfer case is integral to its operation. A fluid leak from the transfer case should be addressed in short order to prevent further damage internally, and to prevent your vehicle from being unusable.