This shows a completely destroyed ring and pinion gear.
This shows chipped teeth, which would make pretty horrendous noise, but keep rollin' on (for awhile)
This pic shows what I mean about pinion teeth vs ring gear: the pinion teeth are very large in comparison.
The orange **** coated on the teeth show the unloaded contact pattern on the ring gear teeth:
As torque is applied to the gears, this contact pattern spreads to encompass the entire tooth, explaining why the entire surface is worn nice and shiny under normal conditions. Note the view is of the "coast" side of the teeth: the lesser important of the two. Also note the very shallow angle of the teeth: gears try to "spread" themselves apart in operation. Modern axles use "hypoid gears" which have distinct advantages: While the coast side teeth are angled steeply, the "drive" side teeth rise almost straight up at right angles. This produces minimum "spread", is a much stronger and long lived concept in gearing.
From this pic, it is obvious the pinion gear teeth are much larger than the ring gear's. This accounts for the commoner tooth failure on ring gears. At the same time, the torque forces on the pinion teeth are 1/4 (approx) of those on the ring, in our example here. Ring gears commonly transmit torque values of several thousand lbs-ft. In fact, when Chevy introduced their 427 cu. in. Corvette in about 1966, their engineers failed to note that the Corvette half-shafts (axles) would be hit with as much as 4000 lbs-ft of torque, almost 4 times the max rating assigned to the U-joints used by their mfr., Dana Spicer. Just about every 427 Corvette produced was handed back to GM with broken rear axle half shafts, UNDER WARRANTY!
