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 such as a drive-on hoist or alignment rack. Verify that the front and rear ride height is within specification.
Calibrate a digital inclinometer by placing it on a clean, flat and level section of the vehicle frame rail and zero the tool. Do not use an analog dial gauge angle/finder protractor to measure rear axle pinion angle, as this may provide an inaccurate reading.
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 this 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 vehicle front with a stand. Support the rear axle assembly using a transmission jack. On both sides, remove and discard the rear shock absorber lower bolts/nuts. Make sure the rear axle is supported before removing the rear spring U-bolts.
Remove and discard the rear leaf spring U-bolt nuts, U-bolt plates and U-bolts. Lower the axle assembly to gain access to the six mm (1.4-inch) spacer on the left side.
Note: the service kit contains all of the parts needed for the adjustment procedure. The rear axle pinion angle can be changed by adding 0.5, one, one-and-a-half, or two-degree rear axle pinion angle shims. The shims are marked as LH and RH. The thicker shims are to only be used on the left side. Thinner shims are for the right side. Use only one shim per side. Make sure that the rear pinion angle is between five to six degrees.
Install the shims on the axle spring seats. To decrease rear axle pinion angle, the thick edge of the shim should face forward. To increase angle, place the thick edge of the shim facing rearward. Make sure that the word FRONT stamped on the shim is facing rearward when increasing angle.
Position and raise the rear axle. Tighten the rear spring U-bolts in a cross pattern with the vehicle resting on wheels/tires at curb height.
Install the U-bolt plates. Tighten the new U-bolt nuts to 98 ft-lb.
Position the rear shocks and install a new lower bolt and nut. Remove the transmission jack and tighten the fasteners to 52 ft-lb.