Differential Man's Products LLC
1080 Valley Street, Suite A
Colorado Springs, CO 80915
Last Update 7-20-2025
Differential Man Products
Office: 719-424-0050
Getting ready to Retire
2025
The Workings of a Differential & Why so much metal in the oil
Hypoid Gears
Why is the Pinion not in the center of the Ring Gear?
Why are the Pinion teeth twice as large as the Ring Gear Teeth? The very first differential had the pinion located in the center of the ring. The teeth kept breaking. The engineers found that if the pinion was offset from the center line, the ring gear teeth had to be longer and thicker, so they would mesh properly with the ring gear. That in turn, made the pinion teeth stronger. By solving one problem, they created another. Tooth wear and a increase of metal particles in the gear oil. This increase the wear of everything, Gears, Bearings, Seals, Axles and even the Internals of the carrier. I've always said, the differential is the only part of the vehicle that is a Metal making machine. Let me explain.
Why is there always metal particles in the oil ?
Spur Gears Helical Gears
Spur Gears and Helical Gears operate differently that the Differential Hypoid Gear. They push against each other in a straight line. But the Differential Hypoid Gear push and wipe against each other. Its the wiping that produces the metal particles. Can't be helped. It's the nature of the Gears. That why its so important to change your oil and use the right lubricant.
1st
Where does the Metal Particles Go?
The Metal Particulates travel with the oil flow. They end up in the strangest places. That's why it takes time to clean the housing the right way. Let's look at all the metal hide-outs.
1st: The Carrier: When the internals wear, the centrifugal force generated inside forces the particles to the inside wall of the carrier.
2nd: As the gear oil is slung up and forward towards the pinion, gravity forces the particles to settle to the bottom of the pinion bearing area. Also, anytime there is metal chunks, they always end up trapped between the two pinion bearings. Just wearing the bearings away!
3rd: As the oil flows over the carrier bearings and shims, it gets trapped between the the tube and the bearing journal. You have to scrape this area when cleaning.
4th: When the vehicle is parked, Gravity causes the particles to settle to the bottom of the housing and collect on the drain plug magnet.
5th: As the metal filled oil travels down the tube, it starts to settle on the bottom of the tube. I always say, the tubes act like a filter. When the metal settle, only clean oil returns.
To clean, I always scrape, soak, and push a solvent rag down the inside.