A right-angle gear pair in which the pinion shaft is offset below or above the gear centerline instead of intersecting it. The offset allows a larger, stronger pinion and lets a vehicle's driveshaft sit lower, but it adds lengthwise sliding along the teeth. That sliding is why hypoid gears need extreme-pressure gear oil and why scuffing is their classic failure.
Hypoid gear in that axle is scuffed on the coast side, somebody filled it with plain gear oil instead of the EP stuff.
Hypoid axles need a GL-5 rated EP oil; plain gear oil in a hypoid set is a fast way to scuff it.
Also heard as
- hypoid
- hypoid set
Related terms
Ring and pinion
Shop name for the hypoid final drive in a vehicle axle, named by its ratio, such as 3.73 or 4.10.
Spiral bevel gear
A bevel gear with curved, oblique teeth that overlap in engagement for smoother, quieter right-angle drives.
Scuffing
Sudden adhesive damage where tooth surfaces weld and tear apart because the oil film broke down.
Pinion depth
How far the hypoid or bevel pinion sits along its axis toward the gear, set with shims behind its bearing.