What mistakes do people make when they build for more power?

Summary:

Jaden says the main mistake, though he does not consider it especially common, is leaving the transmission stock when power or towing load has been added. He also mentions using the wrong parts. His reasoning is that added power or added towing demands heavier duty internals with more holding power than the stock components provide. He illustrates the point with a direct example: build a transmission to stock specification and then put 800 horsepower in front of it, and that transmission is not going to last very long, because it does not have the proper internals for what is being asked of it. His answer frames the transmission as a component that has to be matched to the engine and the intended use, rather than something that can be left untouched while power is added elsewhere in the vehicle.

Answer:

I don't think it's common, but mistakes that people can make when you're building a transmission for power is, yes, leaving it stock. Using the wrong parts. Because if you've got added power or added towing or whatever, you're going to want the heavier duty internals with more holding power than the stock ones. So if you make a mistake of building a transmission stock and then going and putting 800 horsepower in front of it, that transmission's not going to last very long, because you don't have the proper internals for it. That's really what it comes down to. The transmission has to match what's in front of it and what you're asking it to do. If the power went up and the transmission stayed the same, you've built something that can't hold what's being put through it, and it's going to show up as a failure sooner rather than later.