In a rear-wheel drive vehicle, the transmission’s power must be transmitted from the front of the vehicle to the rear wheels. This is done using a driveshaft – a long metal shaft that attaches to the end of the transmission and turns with the rotational speed of the transmission and the engine. However, the driveshaft cannot connect directly with the rear wheels. A differential is used to transform the rotational power of the driveshaft into movement at the wheels. To connect the differential and the driveshaft, a pinion shaft is used.
Depending on the make and model of vehicle in question, there will be one or more pinion seals. One will be located at the inner edge of the pinion shaft, and another (the pinion shaft oil seal) will be located near the end where the pinion shaft attaches to the drive shaft. The point of the seal is to prevent oil from leaking out of the pinion shaft.
All seals are subject to wear and tear, as well as degradation from heat. Eventually, they will fail. Your pinion shaft oil seal is no different. There’s no estimate on how long one should last, though, as there are many different mitigating factors. The seal is in use anytime you’re driving, and your driving habits and the conditions in your area will have significant effects on the longevity of the seal. For instance, if you regularly go off-road with your vehicle, you’ll but a lot more wear and tear on the seal than someone who sticks to the pavement.
The most important tip to remember about your pinion shaft oil seal is that it should be inspected for leaks at every service (your regular oil change, for instance). Once a leak is spotted, the seal should be replaced, as it will only become worse over time. Here are a few common symptoms of a failing pinion shaft oil seal to watch for:
- Wetness at the end of the pinion shaft/driveshaft
- Low differential fluid
- Whining or grinding from the differential while driving, particularly around curves (indicates low fluid)
If you suspect there’s a problem with your pinion shaft oil seal, a certified mechanic can help inspect the system and replace the pinion shaft oil seal if necessary.