F 350 4WD Pickup V8-7.3L DSL Turbo VIN F (1994)
Wheel Hub (Locking): Component Tests and General Diagnostics
Locking and Unlocking Hubs
Manual Locking Hubs
Manual locking hubs are simple to diagnose. Place the transfer case in two-wheel drive and raise the front wheels off the ground. When in the unlocked
position, the wheels should be able to turn freely. Then lock each of the front hubs and rotate the front wheels. The additional load of the drivetrain
components should be felt once the hub has been engaged. In addition, the axle and front driveshafi should be moving along with the wheel Disengage
the hubs and repeat the procedure to check that the hubs have smoothly disengaged.
Automatic Locking Hubs
NOTE: While the vehicle is hoisted, shift into 4WD from a dead stop and not while rear wheels are rotating in order to avoid slamming the hub locks
into the lock position.
Raise vehicle on a hoist so that all wheels are off the ground. Start engine (6007) with vehicle in neutral and transfer case in 2WD. Front wheels should
spin freely by hand. Put transfer case in 4WD and put vehicle in gear. Front and rear wheels should rotate together. Put vehicle in neutral and spin front
wheels by hand in the forward direction. The front axle and front driveshaft should rotate with the wheels. The additional load of the drivetrain
components should be felt once the hub has been engaged. To disengage the hubs, spin the wheels in the opposite direction until an audible "click" is
heard. Spin wheels forward again and they should rotate freely without the axle and driveshaft rotating. Repeat the procedure, only shift into 4WD and
put the vehicle in reverse. This time the hubs should release when the front wheels are spun in the forward direction.
When checking front hubs for proper operation, road test the vehicle to make sure the hubs will remain engaged while under load. This is accomplished
by engaging four-wheel drive and taking the vehicle through several turns (both forward and backward) on dry pavement. This will put an additional
load on the front wheel at the outside of the turn because it is traveling the greatest distance.
Driving through several turns while traveling in different directions will ensure that both sides of the hub teeth have been tested under load. Hubs that are
not sufficiently engaged will "pop" out when loaded. This is due to the driveline releasing windup and is an indication of hub malfunction.
If slippage is suspected, mark the tire and axle with chalk (after locking the hub) and apply a heavy torque load several times. Then inspect your original
indexing marks. If they are no longer aligned, the hubs are not remaining locked when under load. They will have to be replaced.
Should hub locks become submerged in water or mud for a long period of time, water may get past the seals and into the hubs and axle. In this case, all
water must be expelled from the system. The axle must be drained by loosening the axle cover and new lubricant F1TZ-19580-A (WSL-M2C191-A)
used to refill the axle (F1TZ-19580-A has no equivalent).
Disassemble the hubs See: Service and Repair
Repack the wheel bearings See: Wheel Bearing/Service and Repair
and dry off the hub locks. Reassemble hubs.
