Vehicle - Drift While Braking & Steering Diagnosis
Bulletin No. 002/95Issued: 9/21/95
Revised:
Category
R
Applicable Model/s
1991-94 Navajo
1994 B-Series
Subject
DIAGNOSTIC PROCEDURES DRIFT/PULL WHILE BRAKING and STEERING
APPLICABLE MODELS/VINS
1991 - 94 Navajo Model Vehicles
1994 B-Series Model Vehicles
DESCRIPTION
The following procedures update sections "R" or "P" in the workshop manual. Refer to these instructions when troubleshooting "Drift/Pull" while braking complaints.
The contents are as follows:
^ Symptom Descriptions
^ Repair Procedures
^ Parts Information (current at the time of printing)
^ Warranty Information (current at the time of printing)
NOTE:
1. This Service Bulletin contains all current 1991-94 Navajo and 1994 B-Series Steering and Braking Drift/Pull issues and known repair and parts information.
2. Refer to the workshop manual for symptoms other than those described above.
3. READ THIS BULLETIN COMPLETELY PRIOR TO PERFORMING ANY DIAGNOSTICS OR REPAIRS.
4. Place a copy of this bulletin in the applicable workshop manuals.
SYMPTOM A - DRIFT/PULL WHILE BRAKING
GENERAL INFORMATION
Some vehicles may experience pulling/drifting to either side while braking. If a customer complains of this problem, perform the following repair procedure.
REPAIR PROCEDURE
1. Verify the complaint. If the vehicle pulls/drifts while braking, proceed to step 2. If the vehicle pulls/drifts while not braking, refer to Symptom B for diagnostic and repair procedures.
2. Remove the pins from the caliper.
3. Hold the caliper in place against the bottom pin rails. Refer to Fig. 1.
4. Measure the clearance between the caliper and the top pin rails. Clearance should be within 0.5-0.9 mm (0.020-0.035 in.)
5. If the clearance is too small, replace the caliper and measure again. If the clearance is still not within the specified amount, replace the knuckle.
NOTE:
Check the clearance of the new knuckle before installation.
6. After confirming clearance (between the caliper & knuckle), remove both calipers and inner pad assemblies.
7. Remove the anti-rattle clips from the inner pads.
8. Check the side and end clearance with a feeler gauge.
Pad Tab Clearance (Without Anti-Rattle Clips)
MAX MIN
Side 0.5 mm (0.026 in) 0.25 mm (0.010 in)
End 1.2 mm (0.047 in) 1.0 mm (0.039 in)
9. If the pad clearances are within specification proceed to step 12. If not within specification, proceed to step 10.
10. File the backing plate removing equal amounts of material from both sides. Refer to Fig. 3.
WARNING:
Wearing Safety Glasses when filing backing plate.
CAUTION:
Do not grind backing plate. It is possible to remove too much material when grinding.
11. Check the tab clearance.
12. Install the anti-rattle clip on the lower pad tab.
13. Apply a light coat of "anti-seize" solution to the inner knuckle top and bottom pad groove and the caliper rail.
CAUTION:
DO NOT ALLOW ANTI-SEIZE SOLUTION TO CONTACT ROTOR, PAD LINING OR DUST BOOT.
14. Inspect the left and right side radius arm bushings for cuts or deterioration. Replace as necessary.
15. Verify repair. If pulling/drift still occurs, proceed to Symptom "B" - Pull or Drift While Not Braking.
SYMPTOM "A" PARTS INFORMATION
INTERCHANGEABILITY "A" = A new part can be used in place of an old part but an old part can not be used in place of a new part.
SYMPTOM "A" WARRANTY INFORMATION
(Applies To Verified Customer Complaints On Vehicles Covered Under Normal Warranty.)
Warranty Type: A
Symptom Code: 39
Damage Code: 9H
Part Number Main Cause: Refer to Parts Information
Operation Number: YY0072RX
Labor Hours: 1.3 (Left and Right Sides)
SYMPTOM "B" - DRIFT/PULL WHILE NOT BRAKING
GENERAL INFORMATION
This diagnostic procedure should be performed if the first procedure failed to correct the problem or if the vehicle pulled or drifted while not braking.
REPAIR PROCEDURE
1. Prepare the vehicle for road test and adjust the following if necessary:
^ Check that the steering wheel is straight
^ Check tire pressure.
^ Locate flat, straight road.
NOTE:
When road testing, use the same road to and from the starting point. This will cancel cross wind effects on the vehicle.
^ Test drive with the customer or dealer personnel in the passenger seat whenever possible.
^ If the vehicle is equipped with 4WD, unlock the front hubs.
NOTE:
After disengaging the hubs (by pushing the 4X4 button on the dash or rotating both manual locking hubs to the Unlocked" position). It is then necessary to drive twenty (20) feet forward then backward to unlock the hubs.
2. Test drive the vehicle.
NOTE:
The vehicle may experience more than one symptom. Refer to the chart which details the symptoms.
During all braking applications, the driver should keep both hands on the wheel. This will accurately assess the amount of steering wheel movement (pull/drift).
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 1: Tire Mismatch
1. Verify the vehicle's wheel and tire size with that listed on the certification label located on the driver's side B" pillar. If sizes match, proceed to step 2.
^ If the sizes do not match, compare the size to the optional tire size information provided by the Sales Dept.
^ If the sizes do not match, exchange the tires for known good tires (match certification label or optional equipment list).
2. Set tire pressure to the value on the certification label.
NOTE:
Reset tire pressures for front and rear tires. On vehicles with limited slip differentials it may be necessary to measure the tire's circumference to place a matched set of tires on the rear of the vehicle.
3. Spin front tires to ensure hubs are unlocked. If the axle shaft rotates with the tires, the hubs are locked.
4. Switch the front tires (left to right).
5. Road test vehicle. If the pull is not corrected, proceed to step 6.
6. Switch the rear tires (left to right).
7. Road test vehicle. If the pull is not corrected, proceed to step 8.
8. Switch the front and rear tires.
9. Road test vehicle.
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 2: Alignment
1. The vehicle DOES NOT require alignment if the drift or pull occurs ONLY when braking.
2. Check the vehicle for properly matched tires and inflation. Refer to the instructions in steps 1 and 2 of PROCEDURE 1.
3. Measure the front wheel alignment and compare those values to the chart for 1991-92 Navajo vehicles. All other vehicles, refer to alignment specifications.
4. If the vehicle is not within the alignment specification, align the vehicle.
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 3: Tires
1. Spin front tires to ensure hubs are unlocked. If the axle shaft rotates with the tires, the hubs are locked.
2. Measure the circumference of all tires. Install the two closest circumference tires on the rear axles.
NOTE:
Tire pressure must be equal on all tires.
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 4: Steering Gear Valve Off-Center
1. Lift the front wheels off the ground.
NOTE:
Vehicle should be raised so there is no interference with the steering linkage.
2. Straighten wheels and start engine.
3. Observe steering wheel or linkage movement when the engine is started. If movement is observed, proceed to step 4.
4. Spin front tires to ensure hubs are unlocked. If the axle shaft rotates with the tires, the hubs are locked.
5. Stop the engine and install a 0-14000 kpa (0-2000 psi) pressure gauge in the pressure line between the power steering port outlet # 1 and the steering gear inlet port.
6. Start the engine and rotate the steering wheel from stop to stop to bring fluid to normal operating temperature.
7. Check the fluid level in the power steering reservoir, add if necessary. Use Type F ATF (M2CC33F) or equivalent.
8. Turn engine off and recheck fluid level. Add if necessary.
9. Start the engine and run at 1000 rpm.
10. Attach a in-lb torque wrench to the steering wheel nut.
11. Apply sufficient torque in each direction to get a pressure gauge reading of 1723kpa (250 psi).
12. The torque wrench readings should measure the same in both directions. If the difference between the readings exceeds 6 in-lbs. (0.68 Nm), replace the steering gear assembly.
13. Remove pressure gauge.
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 5: Rubber Ball Socket (RBS) Linkage
If the RBS linkage has wind up or memory steer, replace the RBS linkage.
NOTE:
All steering linkage supplied as service parts are the greased steel socket type.
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 6: Brake Imbalance
1. Spin front tires to ensure hubs are unlocked. If the axle shaft rotates with the tires, the hubs are locked.
2. Check the front wheel rotation drag with warm or hot brakes.
^ Make a series of ten (10) stops from 30 MPH
^ Make a series of ten (10) stops with less than thirty (30) second intervals between stops. This procedure will induce a maximum pull if there is a pull/drift problem.
^ Raise the front of the vehicle so that both tires are off the ground.
^ Rotate the front wheels by hand.
^ Both tires should rotate the same amount with little drag. If excessive drag is present, proceed to step 3.
NOTE:
Some drag is natural.
3. Open the bleed screw on the affected wheel to check for residual line pressure. If a squirt of fluid occurs when the bleed screw is loosened and the amount of drag is reduced or eliminated, the master cylinder may not be allowing the brake fluid to return to the reservoir.
^ Check the master cylinder push rod adjustment.
^ Check for full return of the brake pedal after application.
4. Remove both calipers and check the piston retraction using "C" clamps and wooden blocks. The pistons should move easily into the bore when applying force with the "C" clamps. If not, rebuild or replace with new parts.
5. If steps 1 through 4 have not determined the cause of the pull, switch rotors and lining (left to right).
NOTE:
Tab clearance should be checked and, if necessary, modified. Refer to Braking Pull/Drift Repair Procedure.
6. Test drive the vehicle. Perform ten (10) stops from 40 MPH (64 K/H). If there is no change in the pull/drift while braking, the problem is not in the front brakes.
7. Check the rear brakes.
^ Remove the rear wheels and drums.
^ Check for contaminants on brake components (i.e. grease, axle lubrication, leaking brake fluid etc.).
^ Check for broken components, frozen or corroded parking brake cable and improperly installed parts.
^ Check the brake shoe diameter. If either side is out of specification, check for proper function of the adjustment mechanism and repair or replace as necessary.
8. Check the rear cylinders as follows:
^ Install one brake drum and have someone apply the brakes. Check for movement of one of the brake shoes on the wheel that does not have a drum installed.
^ Hold the brake shoe that moved and have the brakes applied again. The other shoe should move.
^ If no movement occurs, repair or replace the wheel cylinder.
^ Install the drum and repeat the procedure on the other side of the vehicle.
9. If the pull/drift still exists, switch the rear shoes (left to right).
10. Test drive the vehicle. If the pull/drift is significantly reduce, replace the rear linings. If the pull/drift is not significantly reduced, go to Procedure 7.
NOTE:
Slight steering wheel movement (right or left) just before the vehicle stops, under hard braking conditions, should be considered normal for twin (staggered mounted) front axles.
SYMPTOM "B" REPAIR INFORMATION PROCEDURE 7: Miscellaneous
1. Check for loose, damaged or excessively worn parts.
2. Visually inspect the front suspension for loose or worn components (i.e. joints, radius arm bushings, radius arm attachments at the axle and frame, alignment adjusters, steering linkage etc.).
3. Repair or replace as necessary.
WARRANTY INFORMATION
(Applies To Verified Customer Complaints On Vehicles Covered Under Normal Warranty.)
Warranty Type: A
Symptom Code: 32
Damage Code: 9H
Part Number Main Cause: 5555 FE 001
Quantity: 0
Description Operation Number Labor Hours
Road Test YY0073RX 0.3
Tire Circumference YY0074RX 0.5
Steering Gear Valve YY0075RX 0.9
Brake Imbalance YY0076RX 2.3
Tire Mis-Match YY0077RX 1.4
Alignment (4 x 4) A0109ECX 1.9
Alignment (4 x 2) A0109FCX 1.9