Nope! Upgrades to a modern tranny nothwithstanding, the 350 is a better tranny than the 400. The timeline has proven that the 400 is overkill, and lots of people are running 500+ horse-lb/ft through 350's with no affect on lifespan of the tranny. I don't know the gear difference--if any between them--but the 350 weighs however many pounds less. (Enough to make a difference.) Also, the 350 has less rotational mass, freeing up additional hp/torque for the back wheels.