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TSB 03-05-99

Axle Diagnosis

Page 3 - Isolate the Condition

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ISOLATE THE CONDITION:  

Refer to the 2000 Jeep Grand Cherokee Service Manual (81-370-0047), Group 3 Differential and Driveline, for additional information regarding the following procedure.

Isolate The Front Axle (if four wheel drive):

1).    Raise the vehicle and support in a safe manner.

2).    For later installation reference, mark the front propeller shaft to the pinion companion flange and the front propeller shaft to the transfer case flange.

3).    Remove the front propeller shaft and lower the vehicle.

4).    Road test the vehicle through the different drive modes.

5).    If the noise decreases or changes in pitch, then the cause of the sound is probably the front axle.

NOTE- THE FRONT AXLE MAY GENERATE SUFFICIENT SOUND THAT THE REMOVAL OF THE FRONT PROPELLER SHAFT MAY CAUSE MINIMUM CHANGE IN THE LEVEL OF THE SOUND GENERATED BY THE FRONT AXLE.

6).    If the sound does not appear to be caused by the front axle, then proceed with the isolation of the rear axle, step 8. If the front axle is determined to be the cause of the sound then proceed to the Axle Inspection and Analysis

Isolate The Rear Axle:

7).    Raise the vehicle and support in a safe manner.

8).    Install the front propeller shaft. Align the previously made marks on the propeller shaft, pinion companion flange, and transfer case flange.

9).    For later installation reference, mark the rear propeller shaft to the pinion yoke.

10).   Remove the rear propeller shaft.

11).   Plug the hole around the transfer case rear output shaft with a shipping plug. Use Snap On kit YA321 or YA2340 for the appropriate size shipping plug.

12).   Secure the shipping plug to the transfer case to prevent possible loosening during the road test.

13).   Lower the vehicle.

14).   If the vehicle is equipped with a NV-242 (Select-Trac) transfer case, then shift the transfer case selector to 4x4 part time.

15).   If the vehicle is equipped with a NV-247 (Quadra-Drive) transfer case, be certain that the transfer case selector is in four high.

NOTE: IT IS NORMAL TO EXPERIENCE A MOMENTARY SHUDDER FROM THE NV- 247 (QUADRA-DRIVE) TRANSFER CASE WHEN INITIALLY PULLING AWAY FROM A STOP WHEN THE REAR PROPELLER SHAFT HAS BEEN REMOVED.

16).   Road test the vehicle through the different condition noted drive modes.

NOTE: KEEP STOP AND GO DRIVING TO A MINIMUM WHILE THE REAR PROPELLER SHAFT IS REMOVED.

17).   If the sound decreases or changes in pitch, then the cause of the sound is probably the rear axle.

NOTE: REPLACE THE NV-247 (QUADRA-DRIVE) TRANSFER CASE FLUID IF A ROAD TEST IS PERFORMED WHERE THE REAR PROPELLER SHAFT HAS BEEN REMOVED. PERFORM THIS FLUID CHANGE ONLY WHEN ALL AXLE REPAIRS ARE COMPLETE AND VERIFIED. ONLY USE AN APPROVED TRANSFER CASE FLUID (PIN 05016796AA) AND REFER TO TECHNICAL SERVICE BULLETIN 21-09-99 FOR FURTHER INSTRUCTIONS.

18). If the sound is still present, then the condition is not axle related and may be coming from other driveline components on the vehicle. Proceeding with this DIAGNOSIS will be of no further assistance.

Axle Inspection and Analysis Procedure:

The axle inspection and analysis is used to gather complete information about the axle in question. It is used to determine whether one or more of the specific problems defined (a gear, a component run out problem, or a bearing) exist within the subject axle. Having identified the type of sound(s) (growl, howl, or whine) should give you an idea of what needs to be checked.

Growl: Check bearings (differential case, pinion gear, axle shaft). Howl: Check runout (pinion gear, ring gear, differential case). Whine: Check backlash measurement, gear contact pattern, and bearing preload.

19).   Remove the wheels and the axle shafts.

20).   Obtain a clean container to drain the axle fluid into.

21).   Remove the differential housing cover.

22).   Inspect the axle fluid for discoloration, burnt, metal filings, etc.

NOTE: THE USE OF UNAPPROVED AXLE FLUIDS AND ADDITIVES MAY CONTRIBUTE TO AXLE SOUND. DUE TO THE UNIQUE PERFORMANCE OF THIS VEHICLE, ONLY MANUFACTURER APPROVED FLUIDS AND ADDITIVES ARE RECOMMENDED.

23).   Place 16 equally spaced marks around the perimeter of the ring gear.

24).   Measure the ring gear backlash at all 16 points. Set the dial indicator against the drive side of the ring gear tooth heel when taking measurements. Record your measurements.

NOTE: IT IS IMPORTANT THAT ALL 16 MEASUREMENTS BE TAKEN, SO THAT THE RING GEAR AND PINION GEAR ARE FULLY CHECKED.

25).   Ring gear backlash should be between 0.13-0.20 mm (0.005-0.008 in.).

26).   The ring gear backlash measurements should not vary by more than 0.05 mm (0.002 in.) between the highest measurement and the lowest measurement. If the backlash variation is greater than 0.05 mm (0.002 in.), then the cause may be runout in pinion gear, a ring gear, or a differential case.

27).   Rotate the pinion gear 10 times, in both directions, with an inch pound torque wrench. Note if the pinion rotates smoothly by observing variation in the torque wrench dial. The torque wrench dial should not fluctuate. A rapid fluctuation of the torque wrench dial may indicate a possible bearing condition. A gradual sweeping like fluctuation of the torque wrench dial may indicate the binding or interference of a component.

28).   Using an inch pound torque wrench, applied to the pinion nut, measure and record the total turning torque required to rotate the pinion gear. Record the measured torque. This measurement is called total torque to rotate or TTR.

29).   Paint the drive and coast sides of the ring gear with Mopar Gear Marking Compound (p/n 04883065).

30).   While placing a load on the pinion gear, rotate the ring gear one full turn in one direction. Note the pattern.

31).   While placing a load on the pinion gear, rotate the ring gear one full turn in the opposite direction. Note the pattern. The areas on the ring gear teeth with the greatest degree of contact against the pinion teeth will squeegee the compound to the areas with the least amount of contact.

32).   Compare the Gear Tooth Contact Patterns. Refer to the appropriate 2000 Jeep Grand Cherokee Service Manual - Group 3 page 3-134 for additional assistance with interpreting the contact patterns.

33).   Install an axle differential housing spreader.

34).   Spread the differential housing and remove the differential case and ring gear. NOTE: DO NOT SPREAD THE DIFFERENTIAL HOUSING OVER 0.50 MM (0.020 IN.). IF THE HOUSING IS OVERSPREAD, IT COULD BE DISTORTED OR DAMAGED.

35).   Rotate the pinion gear 10 times, in both directions, with an inch pound torque wrench. Note if the pinion rotates smoothly by observing variation in the torque wrench dial. If variation is noted, then the pinion bearings may be the affected components.

36).   Using an inch pound torque wrench, applied to the pinion nut, measure and record the pinion turning torque.

37).   Subtract the pinion bearing turning torque measurement from the total torque to rotate measurement (taken in step 28) to obtain the differential turning torque. Record this measurement.

38).   Remove the pinion gear. Inspect the ring and pinion gear set for nicks, chips, burrs, scratches, or high spots.

39).   Inspect each pinion bearing and bearing race for damage or wear.

40).   Compare the match number on the pinion gear to the match number on the ring gear. The match numbers must be the same.

41).   Record the match number and the pinion gear depth variance.

42).   Using a micrometer or caliper, record the thickness of the pinion gear depth shim.

43).   Mark the ring gear to the differential case for possible later installation-reference.

44).   Remove the ring gear from the differential case. Inspect the mating surfaces of the ring gear and differential case for nicks, chips, burs, or high spots.

45).   Install the differential case in to the axle differential housing.

46).   Using a dial indicator, measure and record the differential case flange runout of the ring gear flange (lateral runout check). This measurement is taken on the ring gear side of the differential case flange. The maximum allowed runout is 0.025 mm (0.001 in.).

NOTE: ONLY THE VARI-LOK DIFFERENTIAL CASE IS A TWO PIECE UNIT. IT IS HELD TOGETHER BY ATTACHING SCREWS WHICH ARE COUNTER SUNK INTO THE FACE OF THE DIFFERENTIAL CASE FLANGE. THE COUNTER SUNK HOLES AND SCREW HEADS ARE COVERED OVER BY THE RING GEAR. MINOR RUNOUT VARIATION OCCURS IN THE IMMEDIATE AREA AROUND THE COUNTER SUNK HOLES AND SCREW HEADS.

47).   Using a dial indicator, measure and record the differential case flange center pilot runout (radial runout check). The flange center pilot is the machined lip that is used to center the ring gear on the differential case. The maximum allowed runout is 0.025 mm (0.001 in.).

NOTE: THE COMBINED ASSEMBLY RUNOUT IS 0.051 MM (0.002 IN.), AS MEASURED WITH THE 16 STEP BACKLASH METHOD, BUT INDIVIDUAL COMPONENT RUNOUT MUST BE KEPT TO A TOLERANCE OF 0.025 MM (0.001 IN.).

48).   Using the appropriate special tools, measure and record the pinion depth. Compare this measurement with the previously obtained pinion gear depth shim and the pinion gear depth variance.

49).   Determine what may need to be adjusted or serviced.

 

Page 4 - Repair the condition, verify repair


Thanks to Bob Bergevin for supplying the TSB information

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Last Update: October 25, 1999