Fulltext TSBs

Technical Service Bulletins

TSB
97-6-28
  • NOISE – “RATCHETING” – FRONT AXLE – 4X4 – SELF-ENGAGEMENT OF AUTOMATIC HUB LOCKS – BRONCO, F-150 AND F-250 UNDER 8500# GVW
  • AXLE – 4X4 – “RATCHETING” NOISE – SELF-ENGAGEMENT OF AUTOMATIC HUB LOCKS – BRONCO, F-150 AND F-250 UNDER 8500# GVW
Publication Date: MARCH 17, 1997

LIGHT TRUCK:
1995-1996 BRONCO, F-150, F-250 LD

This TSB article is being republished in its entirety to remove reference to F-250 HD (over 8500# GVW) vehicles.

ISSUE:

A “ratcheting” noise from the front axle and/or a self-engagement of the automatic hub locks may occur on some vehicles. This may be caused by a combination of high axle motoring torque and hub locks which require little torque input to engage.

ACTION:

Reduce the axle motoring torque by replacing the differential side gear thrust washers and adjusting the pinion preload. This procedure will reduce the axle motoring torque to a level below the required hub lock torque to engage. Refer to the following Service Procedure for details.

NOTE:THE FRONT AXLE SHOULD BE “BROKEN-IN” FOR 402 km (250 MILES) PRIOR TO PROCEEDING WITH ADDITIONAL DIAGNOSIS OR REPAIRS. TO BREAK-IN THE FRONT AXLE, ENGAGE FOUR-WHEEL-DRIVE, DRIVE FORWARD AND THEN SHIFT OUT OF FOUR-WHEEL-DRIVE WITHOUT DISENGAGING THE HUB LOCKS. DRIVING WITH THE HUBS ENGAGED WILL BREAK-IN THE AXLE. IF THE VEHICLE IS BACKED UP DURING THIS TIME PERIOD, THE HUB LOCKS WILL DISENGAGE AND WILL HAVE TO BE ENGAGED AGAIN BY REPEATING THIS PROCEDURE.

SERVICE PROCEDURE

Remove the front driveshaft and tie a 12-pound test monofilament fish line between the front output yoke of the transfer case and the round locator hole on the side of the transfer case (Figure 1). Drive the vehicle in two-wheel-drive with the hubs unlocked for a minimum of 3 km (2 miles), including some lock-to-lock figure eight turns. Refer to the following two conditions.


Figure 1 – Article 97-6-28

  • If the fish line breaks, the concern is being generated by the transfer case. It will require further diagnosis and possible repair. Refer to Section C – Transfer Case Diagnosis And Repair of this article.
  • If the fish line did not break, proceed to Section A – Measure The Motoring Torque Of The Front Drive Axle of this article and follow through all of the service procedure until the concern is resolved.

A - MEASURE THE MOTORING TORQUE OF THE FRONT DRIVE AXLE

  1. With the vehicle on a lift, remove both hub locks.
  2. With the left axle shaft free to rotate:
    1. Slowly rotate the right axle shaft in a clockwise direction using the Axle Torque Metering Socket (T96T-3219-A for F-150/Bronco and T96T-3219-B for F-250, found in the 1996 Essential Service Tool Kit), and a dial or beam-type inch-pound torque wrench. Stop at the highest reading, then restart and record the breakaway torque reading. Repeat this procedure in a counterclockwise direction, stopping at the highest reading, then restart and record the breakaway torque reading.
    2. Repeat the procedure in Section A, 2a, for the left axle shaft.
  3. With the left axle shaft held from rotating (place a screwdriver in the U-joint to prevent the axle shaft from rotating):
    1. Repeat the procedure in Section A, 2a.
    2. Repeat the procedure in Section A, 2b.
  4. If all of the torque readings through the differential obtained in Section A, 2a and 2b, are 2.8 N-m (25 lb-in) or less AND if all of the torque readings through the pinion (opposite axle held) obtained in Section A, 3a and 3b are 6.8 N-m (60 lb-in) or less, return the vehicle to the customer and ask that an additional 240 km (150 miles), with the hubs engaged, be put on the vehicle and note any additional occurrence of hub lock self-engagement.
  5. After the 240 km (150 miles) have been driven, repeat Section A, Steps 2 and 3.
    1. If the torque measurements have dropped, the self-engagement should be eliminated.
    2. If the torque measurements have not dropped, and the concern continues, proceed to Section B.

B - FRONT DRIVE AXLE DIAGNOSIS AND REPAIR

  1. If all torque readings obtained in Section A, 2a and 2b, are 2.8 N-m (25 lb-in) or less, the differential side gear thrust washers DO NOT need to be replaced. Proceed to Section B, Step 2.

    If any of the torque readings through the differential obtained in Section A, 2a and 2b, were over 2.8 N-m (25 lb-in), replace the two (2) flat differential side gear thrust washers (Figure 2) with the 0.635mm (0.025″) thick washers supplied with the Axle Motoring Torque Reduction Kit (F6TZ-4228-BA). Follow the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 05-03A for differential and carrier removal instructions.

  2. If any of the torque readings through the pinion (opposite axle held) obtained in Section A, 3a and 3b, are over 6.8 N-m (60 lb-in), measure the pinion bearing pre-load to determine if the pinion should be re-shimmed using the Axle Motoring Torque Reduction Kit (F6TZ-4228-BA).
    1. Follow the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 05-03A for differential and carrier removal instructions.
    2. While the differential assembly is out of the axle housing, check the pinion for smooth, pulse-free rotation.
    3. Slowly rotate the pinion in the carrier using a dial or beam-type inch-pound torque wrench. Stop at the highest reading, then restart and record the breakaway torque reading. Measure and record the torque required to rotate the pinion.
    4. If the breakaway torque is more than 0.7 N-m (6 lb-in) greater than the torque to rotate and/or the pinion rotation is not smooth and pulse-free, inspect the pinion bearings for cage deformation and/or irregular roller or cup wear patterns. Replace the bearing (4621-outer, 4630-inner) if either condition is found.

      NOTE:USE OLD PINION NUT AND WASHER TO ESTABLISH THE SHIM PACK REQUIRED FOR REDUCED PINION TORQUE TO ROTATE. ONLY USE NEW PINION NUT AND WASHER AFTER REQUIRED SHIM PACK HAS BEEN ESTABLISHED.

    5. If the pinion torque to turn is greater than 2.3 N-m (20 lb-in), adjust the shim pack (using the shims provided in the kit) so that pinion torque to turn is 1.7 N-m (15 lb-in). For each thousandth of an inch added to the shim pack, the torque to rotate the pinion will decrease by approximately 0.9 N-m (8 lb-in).

      WARNING:DO NOT ALLOW ANY PINION END PLAY IN THE PINION BEARING ADJUSTMENT.

    6. While the axle shafts are out of the axle assembly, inspect the U-joints for freedom of movement and replace if seized.

      CAUTION:DO NOT USE 80W90 OR 90W GEAR LUBE.

    7. Reassemble the front drive axle following the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 05-03A for differential and carrier installation instructions. Replace the pinion nut and washer with those supplied in the kit. If the ring gear was removed from the differential, replace the ring gear bolts with those supplied in the kit. Fill the axle assembly with 4X4 Gear Oil (F1TZ-19580-A or equivalent meeting Ford specification WSL-M2C191-A).
    8. Recheck torque reading in Section A, Step 2a to verify that axle modifications have been performed properly.
    9. Return the vehicle to the customer and ask the customer to drive the vehicle for 80 km (50 miles) with the hubs locked to “break-in” the modified axle. To break-in axle, engage four-wheel-drive, drive forward, and then shift out of four-wheel-drive without disengaging the hub locks. If the vehicle is backed up during this time period, the hub locks will disengage and will have to be engaged again by repeating this procedure.

      If this procedure has not resolved the concern, call the Self-Engagement Hotline at 1-503-786-5486 (Monday-Friday, 10:00 AM-6:30 PM Eastern Time).

C – TRANSFER CASE DIAGNOSIS AND REPAIR

  1. Check the transfer case for proper amount of Automatic Transmission Fluid (ATF).
  2. Measure the end play of the rear output shaft using a dial indicator. If the end play is over 1.27mm (0.050″), there is a possibility that one (1) of the two (2) rear output snap rings is missing or out of position. Note end play for reassembly purposes. Regardless of end play, proceed to the following Step 2a.
    1. Disassemble the transfer case following the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 07-07.
    2. Inspect for missing or out of place rear output shaft snap rings. Repair or replace as necessary. THIS STEP DOES NOT APPLY TO THE BORG WARNER 4407 TRANSFER CASE.
    3. Check for a minimum of 0.25mm (0.010″) clearance between sprocket and lockup hub on the rear output shaft using a shim gauge. If insufficient clearance exists, replace rear output shaft (-7061-), drive sprocket (-7177-), and hub shift collar (-7100- for manual shift and -7G362- for electric shift).
    4. Inspect the disassembled transfer case for galling in the following locations:
      • Between the drive sprocket bore and the rear output shaft journal. If galling exists, replace both components.
      • Between the sprocket thrust faces, the rear output shaft shoulder and hub shift collar. If galling exists, replace the rear output shaft, sprocket and lockup hub.
    5. Assemble the replacement sprocket and lockup hub on the rear output shaft with a snap ring.
    6. Clean pump screen and magnet.
  3. After reassembly, refill the transfer case with Motorcraft MERCONĀ® Multi-Purpose Automatic Transmission Fluid (ATF) (XT-2-QDX), or equivalent meeting the Mercon specification, to just below the fill plug hole.
  4. If the transfer case diagnosis and repair has not resolved the concern, proceed to Section A – Measure The Motoring Torque Of The Front Drive Axle.

    MOTORING TORQUE MEASUREMENTS AND RECORDING CHART
    BEFORE ADJUSTING FRONT DIFFERENTIAL
    Pinion Bearing Pre-load (N.m or lb-in)__________
    Left Side MeasurementsBreakawayBreakaway
    Right Side FreeClockwise (CW) – _____Counterclockwise (CCW)-_____
    Right Side HeldCW – _____CCW – _____



    Right Side MeasurementsBreakawayBreakaway
    Left Side FreeCW – _____CCW – _____
    Left Side HeldCW – _____CCW – _____



    MOTORING TORQUE MEASUREMENTS
    AFTER ADJUSTING FRONT DIFFERENTIAL
    Pinion Bearing Pre-load (N.m or lb-in)__________
    Left Side MeasurementsBreakawayBreakaway
    Right Side FreeCW – _____CCW – _____
    Right Side HeldCW – _____CCW – _____



    Right Side MeasurementsBreakawayBreakaway
    Left Side FreeCW – _____CCW – _____
    Left Side HeldCW – _____CCW – _____

    The Axle Motoring Torque Reduction Kit (F6TZ-4228-BA) contains the following:

    • Two (2) 0.025″ Differential Side Gear Washers
    • Two (2) 0.005″ Pinion Shims
    • Three (3) 0.003″ Pinion Shims
    • One (1) Pinion Seal
    • One (1) Pinion Washer
    • One (1) Pinion Nut
    • Ten (10) Ring Gear Bolts
    • One (1) Keystone Boot Clamp
    • One (1) Instruction Sheet (I.S. 7144)



    Figure 2 – Article 97-6-28


PART NUMBERPART NAME
F6TZ-4228-BAAxle Motoring Torque Reduction Kit
F1TZ-19580-A4X4 Gear Oil
XT-2-QDXMotorcraft MERCONĀ® Multi-Purpose Automatic Transmission Fluid (ATF)

OTHER APPLICABLE ARTICLES:

NONE

SUPERSEDES:

96-26-20

WARRANTY STATUS:

Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATIONDESCRIPTIONTIME
970628APerform Diagnosis And Road Test (May Only Be Used Once Per Vehicle)0.9 Hr.
970628BCheck Motoring Torque0.7 Hr.
970628CAdditional Time To Re-shim Pinion2.1 Hrs.
970628DAdditional Time To Replace Side Gear Thrust Washers0.4 Hr.
970628EAdditional Time To Overhaul Transfer Case As Outlined4.0 Hrs.

DEALER CODING

BASIC PART NO.CONDITION CODE
422807

OASIS CODES:

509000, 597997, 702100