Lean Correction
Lean Correction
Front and rear lean correction
1. NOTE: When verifying the vehicle lean, all tires must be inflated to the correct specifications and all equipment must be removed from the vehicle, such as tool boxes, caps and bed fuel tanks. The vehicle must also be parked on a level surface.
Inspect all 4 tires for correct inflation, adjust as necessary.
- Refer to the Safety Certification sticker located on driver door jamb.
2. With the vehicle in NEUTRAL, position it on a hoist. For additional information, refer to Vehicle Jacking and Lifting.
3. NOTE: The front and rear springs must be in correct working order before a vehicle lean condition can be correctly diagnosed.
Inspect the front and rear springs for any signs of damage (fractured or broken).
- If a spring is damaged, install a new spring and re-evaluate the vehicle.
- If the lean condition is not corrected, proceed to Step 4.
4. With the vehicle on a level surface and the suspension at curb height, measure from the wheel lip to the top of the wheel well opening at all 4 corners. Record the measured values.
5. Using the front wheel well opening measurements, take the smaller measured value and subtract it from the larger measured value, this is the wheel well difference number. Record this number.
- Repeat the calculation using the rear measurements.
6. Measure chassis ride height and record the measured values. For additional information, refer to Ride Height Measurement Ride Height Measurement.
7. Using the front chassis ride height measurements, take the smaller measured value and subtract it from the larger measured value. This is the chassis ride height difference number. Record this number.
- Repeat the calculation using the rear measurements.
Front lean correction
NOTE: Correcting the front or rear lean condition will have an effect on the other lean condition.
NOTE: If the recorded front wheel well difference number is greater than the rear, correct the front lean condition before correcting any rear lean conditions.
8. Remove the high side front coil spring.
9. Compare the height of the original front coil spring with a new one with the same part number. Note the difference.
10. Compare all 3 front coil springs and select the 2 most evenly matched for installation.
11. From the 2 most evenly matched coil springs, select the tallest and install it on the lower side of the vehicle. Install the shorter of the 2 on the higher side of the vehicle.
Front Lean Correction Chart
12. If the original front coil spring exceeds the height of the new spring by 13 mm (1/2 in), install the new front coil spring in the vehicle. For additional information, refer to Front Suspension &/or Steering Knuckle (Rear Wheel Drive (RWD) vehicles) and Front Suspension &/or Steering Knuckle (Four-Wheel Drive (4WD) vehicles).
13. If the original front coil spring is shorter than the new spring by at least 13 mm (1/2 in), remove the low side front coil spring from the vehicle. For additional information, refer to Front Suspension &/or Steering Knuckle (RWD vehicles) and Front Suspension &/or Steering Knuckle (4WD vehicles).
Rear lean correction
NOTE: If the recorded rear wheel well difference number is greater than the front, correct the rear lean condition before correcting any front lean conditions.
14. Using the recorded wheel well difference numbers, the recorded chassis ride height difference numbers and the following repair action chart, determine what repair action is needed to correct the vehicle lean condition.
Rear Lean Correction Chart
- If shim installation is required, continue with this procedure.
15. Support the axle.
16. Remove and discard the 4 nuts and 2 U-bolts to allow the rear axle to separate from the rear spring.
17. Turn the shim so the recess is facing upward.
18. Insert the shim between the rear spring and the spring seat.
- Position the shim so the center bolt through the spring leafs is in the shim recess, the stud on the bottom of the shim is in the spring seat recess and the shim is aligned with the rear spring.
19. Install 2 new U-bolts and 4 new nuts. Tighten the nuts evenly in a cross-type pattern in 4 stages.
- For F-250 and F-350:
- Stage 1: Tighten to 50 Nm (37 lb-ft).
- Stage 2: Tighten to 100 Nm (74 lb-ft).
- Stage 3: Tighten to 150 Nm (111 lb-ft).
- Stage 4: Tighten to 200 Nm (148 lb-ft).
- For F-450 and F-550:
- Stage 1: Tighten to 100 Nm (74 lb-ft).
- Stage 2: Tighten to 200 Nm (148 lb-ft).
- Stage 3: Tighten to 300 Nm (221 lb-ft).
- Stage 4: Tighten to 400 Nm (295 lb-ft).
20. Remove the support from the axle.
21. Install new spring(s) as necessary.