Service Procedure

1. Drive the vehicle and verify the condition. Record all speeds, engine rpms and transmission gears that correspond to any boom, rumble or vibration that occurs. Note if the condition is cyclical, or if the condition severity changes by changing from 2H to AWD and 4H or by changing gears (3rd or OD), or the condition changes from cruise to coast and/or tip-in or tip-out.

2. Verify tire pressures are 207 kPa (30 psi) in the front tires and 241 kPa (35 psi) in the rear. If incorrect, correct tire pressure and redrive. If condition is not resolved, exchange all four tires with those of another Expedition or Navigator with same powertrain and wheel configuration which does not exhibit the condition. Redrive or properly calibrate wheel balancer and check the balance of the tires without removal of the factory weights. If tires are out of balance, rebalance and drive the vehicle. If the condition is not resolved, proceed to Step 3.

3. Both the driveshaft and the rear axle flange will have yellow paint dots. Verify that the driveshaft yellow dot and the rear axle flange yellow dot are aligned. If not aligned, rotate driveshaft at the rear axle flange so that the yellow dots are aligned and redrive. If the condition is still present, measure the driveshaft runout at both ends and in the middle. If the runout is over 0.030" at any location, replace the original double carden driveshaft with a new heavy duty single carden Driveshaft (XL1Z-4602-AA - 5.4L engine or XL1Z-4602-BA - 4.6L engine) and redrive. If the condition is still present, disconnect the driveshaft at the rear axle and measure the rear axle flange runout per the 1997 Expedition Workshop Manual, Page 205-00-25. If the flange runout is out of specification (spec is 0.011"), consult the Sterling Axle Plant Hotline at (800) FORD-AXL. Otherwise, proceed to Step 4.

4. Index the driveshaft in 90 degree increments around the rear axle flange and drive the vehicle after each reindexing. If condition is not resolved, reindex the driveshaft so that the yellow dot is aligned with the yellow dot on the rear axle flange and proceed to Step 5.

NOTE
AFTER CONDUCTING STEPS 1-4 AND ENSURING THAT THE CONDITION IS NOT ORIGINATING FROM THE TIRES/WHEELS AND/OR DRIVESHAFT, IT IS POSSIBLE THAT THE CONDITION COULD BE ORIGINATING FROM THE TRANSFER CASE. A TRANSFER CASE CONDITION IS TYPICALLY CHARACTERIZED BY A NOTICEABLE INCREASE IN THE SEVERITY OF THE VIBRATION FROM AN ACCELERATION/COAST TO A DECELERATION DRIVE MODE. IF THE VIBRATION CONDITION BEING EXPERIENCED IS SIMILAR TO THIS VIBRATION, COMPLETE STEPS 5-7 TO IDENTIFY IF THE TRANSFER CASE IS CONTRIBUTING TO THE CONDITION.

5. Transfer case testing is as follows:

a. Index the rear driveshaft in 45 degree increments at the transfer case only (maintain the same alignment with the rear axle flange) and redrive between each index. Note if the condition severity changes. This process may reach a point where the vibration is eliminated and/or reduced to an acceptable level.

Does the condition disappear or change significantly?

^ If yes, return vehicle to customer.

^ If no, or customer returns unsatisfied, proceed to Step 5b.

NOTE
THE TRANSFER CASE REAR OUTPUT MUST BE PLUGGED SO THAT FLUID DOES NOT SPILL DURING VEHICLE OPERATION. USE PLUG F75Z-7H408-AA.

b. Completely remove the rear driveshaft from the vehicle and redrive in 4H mode so that the vehicle is being driven through the front driveshaft only.

Does the condition disappear or change significantly?

^ If yes, proceed to Step 6.

^ If no, proceed to Step 7.

6. If not already done in Step 3, replace the carden rear driveshaft with a heavy duty single carden driveshaft (refer to Step 3). When installing the new driveshaft, be sure to align both the driveshaft and rear axle flange yellow paint dots. Redrive vehicle in 2H at highway speeds to verify the condition has disappeared or improved significantly. If the double carden driveshaft was replaced in Step 3, or after completing Step 6, the redrive resulted in little or no improvement, proceed to Step 7.

NOTE
REAR DRIVESHAFT REMOVAL IS FOR TEMPORARY TEST USE ONLY AND IS NOT RECOMMENDED FOR LONG DURATIONS OF TRAVEL. WHILE DRIVING IN THIS CONDITION, NOISE AND VIBRATIONS WILL BE EXPERIENCED AT VARIOUS SPEEDS THAT MAY NOT HAVE BEEN NOTED PREVIOUSLY. THE PURPOSE OF THIS TEST IS TO DETERMINE IF THE ORIGINAL CONDITION HAS BEEN CHANGED.

7. If the vehicle was built on or before 7/15/97, call the Transfer Case Hotline at (765) 286-6234 to request a certified transfer case. Calls to the hotline will be screened to ensure that the diagnosis in this TSB article has been followed thoroughly and properly. If your vehicle is a good candidate for a transfer case exchange, a certified transfer case will be shipped to your dealership. Install the certified transfer case into the vehicle and redrive. If the condition is not resolved, or the vehicle was built after 7/15/97, proceed to Step 8.

8. Call the Sterling Axle Plant Hotline at (800) FORD-AXL for a certified rear axle. If new axle does not completely correct the concern, repeat Step 4 and index the shaft to the axle.