Quote:
Originally Posted by blykins
I would refrain from using absolutes...
I have numerous 600's in road race, drag race, and super hot street stuff and have never had a customer break a gear. This is up to 600-650 hp, launching on wrinkle walls and shifting at 7000.
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I understand what you are saying Brent and while the third gear breakage was (to my knowledge) not experienced at launch in first or third gear it was experienced in a gear change from second to third, in a drag car, with a medium power level (but torquey) big block, in a heavier car than a Cobra.
The Tremec designed third gear misalignment in their TKO600 transmissions unnecessarily loads the engaged third gear, gear teeth higher than they would otherwise be loaded with a full face contact design. Whenever you do that to a driving and driven set of gears they will fail sooner than the same gears with full face contact — it's just the mechanics of the gear system. This is a similar phenomena to getting the pinion depth wrong on a ring and pinion. Will they fail right away? Probably not. Will they fail sooner than a properly set up ring and pinion, yup.
While it is not an absolute that you will get shot every time you play Russian Roulette, it is true that the more often you play the more likely you are to get shot, again sort of a similar phenomena here. I think the number of Cobra's who can load their third gear, gears to their breaking threshold is relatively small, more because of the car weight and the spectacular experience available in car at WOT in third gear. That however does not mean that they will not fail. Importantly if and when they do fail the attendant gear tooth shrapnel is capable of expanding the scope of the failure if it gets into other gear sets inside the transmission.
So where is that magic line in the sand you don't want to cross? I can't say with any certainty. We do know Tremec claims the transmission is rated at 600 ft/lbs. They don't say if that is true for all gears some gears or only one set of gears. They also, to my knowledge, don't say if that is a sustained torque loading or a shock loading like we might see launching the car in a drag race style fashion. My suspicion (and that's all it is — a suspicion) is it is a continuous duty loading for a single gear set probably first gear.
If that is true (and that's a big if) it means 600 ft/lbs of torque and more represent a potential component failure threshold in third gear, again if everything is hooked up and really transmitting that much torque. How often can you do it with the misaligned gears? I don't believe there is any test data to give insight to that elusive number. However, we do know it happens and we do know those gears are misaligned 0.140" (if you believe Tremec).
Does this mean we should all forsake our TKO600's, probably not. Is it appropriate to make the knowledge available to someone who is contemplating the purchase of a new Tremec transmission? I think so. I know I would have liked to have had the knowledge before spending my monies and I think others might also. Will it or should it change everyone's mind? I doubt it and I don't think so but it will make some reconsider what they are about to buy and potentially allow them to make a better decision — for themselves.
In the final analysis if you are going to spend $2,400+ on a transmission why not buy the most robust unit with the highest torque rating and the best shifting qualities that will fit into your car for the dollars that you are about to spend?
Ed