GM had great sales for a time with the Hummer brand. The economy has foreclosed on that segment of the market, and GM has sold the brand to a Chinese company. However, there are lots of Hummer H3s around and no dealer body to repair them, which sounds like opportunity for the transmission shop.
The Hummer H3 was available with either an automatic or manual transmission and used a 4493/4494 transfer case manufactured by BorgWarner. The 4493 and 4494 are operationally the same transfer case, a three-position, electrically shifted unit. The 4493 has a 2.64 low-gear ratio and the 4494 has a 4.1 low-gear ratio, which makes it a good rock crawler for the off-road guys. This obviously means that the internal gear trains will be different.