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Originally Posted by eschaider
When ever you transmit power through two gears the heat treatment, gear material, tooth design, gear face (tooth) width and center to center distance between the two gears determines their strength and ultimate torque transmission capability.
Remember how to determine load capacity for the gear set from my paragraph above. If you cut the face contact by 50% you have 50% of the torque capacity of the same gear set with full face contact. Why do you think Tremec lines up all the other gear sets correctly. Third is the bastard child, sacrificed for manufacturing cost reductions.
Because we do not use these transmissions like grandma on her way to church the continuous load failure model can be misleading. The shock loads on a gear change under power are much more damaging to the transmission than a continuous load from the same engine car combination. This is further aggravated if your tires are hooked up with a good clutch and a clean but fast shift into third gear. That clean fast shift puts spectacular momentary loads on the gear. Anything less than full tooth contact is a significant reduction in gear life.
Unlike Keisler's representation of a missed shift causing the damage, quite to the contrary a clean shift under power with the tires hooked up and enough torque is what will kill third gear.
From what Tremec told me the TKO500 and TKO600 both suffer the misalignment.
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We are not talking about a 50% reduction in tooth contact area, maybe a 5-10%, and I'm not sure that at these smaller levels of misalignment the reduction in strength is linear with the reduction in contact area (length). You may be right though. A mechanical engineer needs to respond. The failure may have occurred even if the gears were aligned properly, but that still doesn't excuse the misalignment issue.
In addition, although I think the torque capability is related to the distance between gears, I would think specifically, it's the radius of each gear factoring in the amount of torque multiplication, based on its ratio, which determines the actual force on the gear teeth, possibly different for each gear set. If you have 500 ft lbs out of the engine, if 1st gear is 3:1, then you should have close to 1500ft-lbs coming out the tail shaft. The actual forces on all the teeth from the input shaft to the output shaft should be calculatable, because the power is being transmitted through 4 gears ( two sets of gears). This would give the relative loading of each specific gear.