F 150 2WD Pickup V8-4.6L CNG SOHC VIN 9 (1997)
Pinion Gear: Testing and Inspection
Rear axle universal joint flange runout should be checked when all other checks have failed to show the cause of vibration.
Another cause of excessive rear axle universal joint flange runout is improper installation of the rear axle drive pinion seal. Check to see if the spring on
the seal lip has been dislodged before replacing the differential ring gear and pinion.