TSB Article No. 03-14-3
SUSPENSION - 4X4 WHEEL HUB NON-ENGAGEMENT/DISENGAGEMENT
2000-2003 EXCURSION, SUPER DUTY F SERIES
Some 2000-2003 F-250/350 and Excursion 4X4 equipped vehicles may experience a condition where the front hubs will not engage or disengage properly. It is possible that the vacuum necessary to operate the hub is being restricted.
Insure that the flow of vacuum is not being restricted through the hub. Perform Workshop Manual diagnosis per Section 308-07-A Pin Point Test G. If no problems are found in Pin Point Test G, perform the following procedure to relieve restriction in the vacuum path through the wheel end.
1. Remove both wheel hub assemblies (See WHEEL HUB removal procedure under Section 204-01B: FRONT SUSPENSION).
2. Remove thrust washer located between the wheel hub assembly and the axle constant shaft (This gray plastic thrust washer is approximately 2-3/4" OD, and has four slots on the back side).
NOTE KNUCKLE SEAL DOES NOT NEED TO BE REPLACED FOR THIS PROCEDURE.
3. File four (4) 1/8" to 1/4" "KEYWAYS" into the inside diameter of the thrust washer.
NOTE THE THRUST WASHER REQUIRES ONLY A LIGHT FILM OF GREASE. REMOVE ANY EXCESSIVE GREASE FROM WASHER, AND CAVITY BEFORE INSTALLATION.
NOTE THE ADDITION OF THE KEYWAYS AND THE REMOVAL OF EXCESSIVE GREASE WILL ALLOW VACUUM TO PASS, UNRESTRICTED, FROM THE KNUCKLE, THROUGH THE HUB, AND TO THE HUB LOCK.
4. Reassemble wheel end per Workshop Manual Section 204-01B.
NOTE DURING RE-ASSEMBLY, REPLACE YELLOW BEARING 0-RING WITH PART NUMBER F81Z-A322-AA. REPLACE HUBLOCK 0-RING WITH PART NUMBER F81Z-1K106-AA. THE 0-RINGS ARE CRUCIAL FOR PROPER VACUUM SEQUENCE OPERATION AND FUNCTION OF THE HUBLOCK.
TSB Article No. 03-4-1
FRONT LOCKING HUBS - SERVICE TIP
1999-2003 SUPER DUTY F SERIES
Article 00-8-6 is being republished in its entirety to update the model year coverage.
This TSB provides information on the 4X4 system, particularly the front locking hubs.
Refer to the following text for information regarding the 4X4 system and the front wheel hub locks.
4X4 ESOF LOCKING HUB: DIAGNOSTIC AND SERVICE ISSUES
Many system components are involved in proper operation of the ESOF (Electronic Shift-On-The-Fly) locking hubs on 1999 and newer Super Duty and Excursion 4X4 vehicles. Before diagnosing the hub locks themselves as the cause of 4X4 concerns, be sure to verity all related system components.
HUB LOCK OPERATION
The Super Duty and Excursion 4X4 ESOF system uses timed vacuum sequences to lock and unlock the wheel ends. A high vacuum level is used to engage the hub locks, and a lower vacuum level is used to disengage the hub locks, after which the vacuum is released, and the hub lock holds itself in the proper mode. The vacuum signals are supplied to the hub locks by system components, including Generic Electronic Module (GEM), wiring harness, solenoid, vacuum harness, and vacuum seals. As a first step in service, eliminate such obvious items as loose wiring connections, loose vacuum connections, or damaged vacuum lines.
"Slow" release of the hub locks is not considered abnormal for this system. Anytime vacuum is applied to the hubs, whether for 4X4 or 4X2, the hub locks will initially engage. If 4X4 was requested, they will remain engaged, but if 4X2 was selected, the internal mechanism will release only after the GEM timers expire and vacuum is vented from the hub. This normally takes 15 seconds, but can take up to 2 minutes depending on how the 4X4 mode switch was operated. After the hub mechanism releases, internal springs must work the hub lock gears to the disengaged position. Road bumps, vehicle speed, acceleration cycles, or momentary reversal of direction can assist this process, varying the length of time the hub locks remain engaged in each situation.
The hub locks have manual override selector dials which, when rotated to the "lock' position, will keep the mechanism locked regardless of the instrument panel 4X4 mode switch position. Verify that both dials are in "auto" before evaluating ESOF operation.
MATCHING PAIRS NOT REQUIRED
Left and right side hub locks are not connected other than by the common vacuum supply line. If a malfunction in either hub lock is diagnosed, it should be replaced as an individual unit; there is no need to "balance" an axle with new hub locks on both sides. If both sides appear to be malfunctioning, be sure to verify upstream system integrity before replacing both hub locks.
HUB LOCK REMOVAL
After removing the hub lock retaining ring, be sure not to use tools other than hands or "grip" gloves as damage may occur to either the paint or function of the hub lock. Pliers or channel locks should be only considered as a last resort as they will usually damage the hub lock, making replacement necessary.
If contamination (water, mud, etc.) is found in the hub cavity, look for the source. If it is due to system leaks other than the hub lock, they must be found and repaired. Always replace the hub lock 0-ring before re-use.
If a torsional failure (twisting fracture) of the hub lock is suspected or the internal gears are "shattered", the axle constant shaft may have been damaged as well. Inspect the axle shaft carefully; if twisting has occurred at the base of the axle splines, it is difficult to see without removing the bearing assembly.
If a "ratcheting" noise is found especially over road bumps and potholes, suspect the needle bearing that supports the inboard end of the axle constant shaft within the hub/bearing assembly. Eliminate this as a cause before servicing the hub lock. Wear at this bearing can set up vibration, which may be heard as ratcheting, while a seized bearing can bind the shaft, forcing it to rotate in 4X2.
Plastic? Really? Wow, next to the Edsel and the 255 v8, possibly the dumbest thing Ford ever did