For a Dana 80 rear axle, here's some info out of my manual:
PINION SEAL
REMOVAL
(1) Raise and support the vehicle.
(2) Scribe a mark on the universal joint, pinion
yoke, and pinion shaft for reference.
(3) Disconnect the propeller shaft from the pinion
yoke. Secure the propeller shaft in an upright position
to prevent damage to the rear universal joint.
(4) Remove the wheel and tire assemblies.
(5) Remove the brake drums to prevent any drag.
The drag may cause a false bearing preload torque
measurement.
(6) Rotate the pinion yoke three or four times.
(7) Measure the amount of torque necessary to
rotate the pinion gear with a (in. lbs. ) dial-type
torque wrench. Record the torque reading for installation
reference.
(8) Hold the yoke with Wrench 6719. Remove the
pinion shaft nut and washer.
(9) Remove the yoke with Remover C-452 (Fig. 22).
(10) Remove the pinion shaft seal with suitable
pry tool or slide-hammer mounted screw.
INSTALLATION
(1) Clean the seal contact surface in the housing
bore.
(2) Examine the splines on the pinion shaft for
burrs or wear. Remove any burrs and clean the shaft.
(3) Inspect pinion yoke for cracks, worn splines
and worn seal contact surface. Replace yoke if necessary.
NOTE: The outer perimeter of the seal is pre-coated
with a special sealant. An additional application of
sealant is not required.
(4) Apply a light coating of gear lubricant on the
lip of pinion seal.
(5) Install new pinion shaft seal with an appropriate
Installer.
NOTE: The seal is correctly installed when the seal
flange contacts the face of the differential housing
flange.
(6) Position pinion yoke on the end of the shaft
with the reference marks aligned.
(7) Seat yoke on pinion shaft with Installer D-191
and Yoke Holder 6719 (Fig. 23).
(8) Remove the tools and install the pinion yoke
washer and nut.
(9) Hold pinion yoke with Yoke Holder 6719 and
tighten shaft nut to 597 N·m (440 ft. lbs. ) (Fig. 24).
Rotate pinion shaft several revolutions to ensure the
bearing rollers are seated.
(10) Rotate the pinion shaft using an inch pound
torque wrench. Rotating resistance torque should be
equal to the reading recorded, plus a small amount
for the drag the new seal will have (Fig. 25).
NOTE: The bearing rotating torque should be constant
during a complete revolution of the pinion. If
the rotating torque varies, this indicates a binding
condition.
(11) Install the propeller shaft with the installation
reference marks aligned.
(12) Tighten the universal joint yoke clamp screws
to 19 N·m (14 ft. lbs. ).
(13) Install the brake drums.
(14) Add gear lubricant to the differential housing,
if necessary. Refer to the Lubricant Specifications for
gear lubricant requirements.
(15) Install wheel and tire assemblies and lower
the vehicle.
Pinion Bearing Preload - Original Bearings 1-2 N·m (10-20 in. lbs. )
Pinion Bearing Preload - New Bearings 2. 8-5. 1 N·m (25-45 in. lbs. )
Pinion Nut 440-500 ft-lbs
Hope this helps...