The transfer case output shaft seal is located on the transfer case of vehicles with four-wheel drive. This transfer case allows you to switch between two-wheel drive, neutral, to, low four-wheel, and drive four-wheel drive. The case consists of a chain drive and gear reductions. The transfer case uses the chain drive and gear reductions to transfer power from the transmission to either the rear differential or front differential, depending on what the wheel drive the driver chooses operate in.
The purpose of the transfer case output seal is to keep fluid from leaking out of the input shaft from the transmission. In addition, it helps to keep fluid from leaking out of the front and rear output shaft to the differentials. This keeps everything lubricated so it runs properly.
If one of these seals should leak, fluid will escape onto the transfer and it is no longer able to cool and lubricate the components. Ultimately, the internal parts will overheat, seize up, and fail. When this happens, the four-wheel drive will not work at all. It is recommended that your transfer case fluid should be changed every 30,000 miles, so your seals should be inspected during this time for any signs of wear.
The transfer case does not have a fluid level indicator, so if you do notice any fluid that is reddish in color beneath your vehicle it may be that you have a leaking seal. Since the transfer case output shaft seal can go bad and wear, it is important to know the symptoms so you can recognize them before they completely fail.
Signs that indicate your transfer case output shaft seal needs to be replaced include:
Difficulty shifting into gear
There is noise coming from all of the gears
The vehicle jumps out of low four-wheel drive mode
You notice a reddish fluid underneath your vehicle
Grinding noise from the middle of your vehicle while driving
The transfer case will not shift between two-wheel and four-wheel drive
If any of the above problems arise, have a certified mechanic replace the failing transfer case output shaft seal on your vehicle to eliminate any further problems with your vehicle.
This article originally appeared on YourMechanic.com as How Long Does a Transfer Case Output Shaft Seal Last? and was authored by Valerie Johnston.