I just bought a TH475 transmission which comes with a drum parking brake attached, and the yoke is a bolt on type. The transmission comes from a motorhome with only 35k miles on it. These transmissions are installed for pretty heavy use, so have straight cut planetary gears- a bit stronger, but possibly a bit noisier. However, this trans is going behind a blown BBC, so a little gear whine shouldn't be too much of a burden. Now, what I want to know is exactly what the situation is regarding changing from bolt on to slip on yoke. On the interbabble there are conflicting stories, but the consensus seems to be that a slip on yoke that has the splines counterbored into the yoke by about an inch to 1.5" is the answer. And then you see, "except for motorhomes". So, what's the story here?