Some 2019-2021 Ford Ranger vehicles may exhibit a shudder/vibration when accelerating from a stop. This may be due to an excessive rear axle pinion angle.
Park the vehicle on a level surface (drive-on hoist or alignment rack). Verify that the front and rear ride height is within workshop manual specifications. If the ride height is within spec, calibrate a digital inclinometer by placing it on a clean, flat and level surface of the vehicle frame rail and zero the tool. Do not use an analog dial gauge angle finder protractor to measure the rear axle pinion angle.
To simplify taking the measurements, rotate the driveshaft until the rear axle pinion flange yoke is parallel to the floor. Take the rear axle pinion angle measurement from the horizontal face of the rear axle flange yoke and record as angle A.
Subtract angle A from 5.25 degrees to determine the appropriate shim required to adjust the rear axle pinion angle.
Support the front of the vehicle with a stand. Support the rear axle assembly. On both sides, remove and discard the rear shock absorber lower bolt and nut. Be sure to support the rear axle before removing the rear spring U-bolts.
Remove and discard the rear leaf spring U-bolt nuts on both sides. Remove the rear leaf spring U-bolt plates. Remove and discard the U-bolts.
Lower the axle assembly to gain access to the ¼-inch spacer on the left side and remove the left side spacer.
Note: The service kit KB3Z-4C088-B contains all of the parts necessary for the adjustment procedure. The rear axle pinion angle can be changed by adding 0.5, 1, 1.5 or 2 degree rear axle pinion shims. The shims provided in the kit are marked as LH and RH to identify vehicle sides. The thicker rear axle pinion shims are to only be used on the left side of the vehicle. The thinner shims are for the right side.
Use only one shim per side. Make sure that the rear axle pinion angle is between 5.00 – 6.00 degrees. Install the desired shims on the axle spring seats based on the previously calculation (subtract angle A from 5.25 degrees).
To decrease rear axle pinion angle, the thick edge of the shim should be facing forward. To increase pinion angle, the thick edge of the shim should face rearward. Make sure that the word FRONT (stamped on the shim) is facing rearward when increasing pinion angle.
Position and raise the rear axle. Tighten the rear spring U-bolts in a cross pattern with the vehicle resting on the wheels/tires, at curb height. Position the new U-bolts. Install the leaf spring U-bolt plates. Install the new U-bolt nuts, tightening to 98 ft-lb.
Position the rear shock absorbers and install new lower bolts and nuts. Remove the transmission jack and tighten it to 52 ft-lb. Remove the support from the vehicle front.
