The NP 208 transfer case is a full-time unit that attaches directly to the back of the automatic transmission on a four-wheel drive vehicle. Full-time means that the vehicle has four-wheel drive at all times. The NP 208 has a built-in differential that allows the front and rear axles to move at different speeds on the pavement. When driven off-road, it has a "lock" function that locks the front and rear axles together for improved traction. It can be found on various Chevrolet, Dodge, Ford, and Jeep products from 1980 to 1988. A bad rear output seal will allow lubricant to leak out where the rear drive shaft meets the transfer case. Lubricant loss can, of course, damage the unit.
Park the vehicle on a level, paved surface. Place the transmission in park, and set the parking brake. The vehicle should be high enough off the ground so that you will not need to use a jack and jack stands in order to make the repair. If you want extra clearance, raise the front of the vehicle with a jack and support with jack stands.
Use a wrench to remove the bolts from the u-joint straps where the drive shaft connects to the output yoke on the transfer case. Remove the straps. Pull the u-joint and drive shaft out of the yoke. Tie a piece of wire to the frame. Tie the other end to the drive shaft to keep it out of the way.
Use a ratchet and socket to remove the output yoke nut and washer from the center of the yoke. Paint a mark on the output shaft and the yoke with white-out. This will allow you to install the yoke in its original position. Pull the yoke from the output shaft. The output seal is now exposed. Use a flat screwdriver to pry out the old seal.
Spray parts cleaner on a shop rag and clean the area in the transfer case where the seal fits.
Coat the outside rim and inside lip of the new seal with a thin coat of all-purpose grease.
Fit the new seal against the transfer case. Place a large socket that is as close to the size of the outside diameter of the seal as possible. Tap the back of the socket with a hammer to drive the seal into the transfer case.
Spray parts cleaner on a shop rag and clean the outer surface of the yoke. Place a thin film of all-purpose grease on the yoke. Line up the marks you painted on the yoke and output shaft and slide the yoke onto the shaft, being careful not to damage the lip of the new seal.
Install the washer and nut on the yoke. Use a torque wrench and socket to torque the nut to 110 foot-pounds. Mount the u-joint and drive shaft back in the yoke. Install the retaining straps and bolts. Tighten the bolts. If the vehicle is on jack stands, raise the front end with a jack, remove the jack stands and lower the vehicle to the ground.
