I often get questions about high pinion axles and low pinion axles and what the advantages are and what exactly is meant by the terms. I though I would start off the axle tech forum with a brief and simple explanation of both and what the terms mean and how they are important.

What is a high pinion axle? High pinion and low pinion reference where in relation the pinion gear is located within the housing based on the centerline of the ring gear. High pinion axles have the pinion gear located above the centerline of the ring gear and a low pinion is located below the centerline of the ring gear.

Why is this important? First and foremost the importance is in terms of ring and pinion strength. When a low pinon axle is used on the front position of a four wheel drive vehicle, the ring gear is spun backwards. This is important because the ring gear teeth are curved. A simple geometry lesson tells us the convex side is stronger because the load is equally distributed throughout the length of the tooth. This can be verified by comparing the ring gear tooth to a dam holding back a lake. The convex side goes towards the load. The high pinion axle uses a reverse cut gear, and when used in a front position, the convex side becomes the drive side again, and the concave side becomes the coast side. Consequently, a high pinion axle located in the rear position of a vehicle is spinning backwards, and again the strong side of the tooth and the weak side of the tooth are switched.

Is there any other advantage to a high pinion? Yes, another advantage is that the driveshaft location tends to be noticeably higher because it is above the centerline of the ring gear, as much as 4-5" higher in some vehicles. This can be an advantage where ground clearance is important, and also a better driveline angle can be acheived. This can be especially important on shorter front driveshaft vehicles such as Jeep ZJ's and XJ's, which tend to devolop driveline vibrations when lifted above 4" with a low pinion front axle.