You need to drain the primary and pull the cover, then remove the jackshaft.
#1 drain the primary
#2 remove the primary cover
#3 You will see the starter jackshaft at the top of the ring gear. Jam a flat head screwdriver in there to keep it from turning, and remove the 1/4-20 bolt holding it on. There may be a tab bent over the bolt to keep it from turning. If so, pry it open with the screwdriver. Pay attention to how the jackshaft goes together. When you re-assemble it, only torque it to 12 ft/lbs, which is very little. Use an inch-lbs wrench (12 ft/lbs = 144 in/lbs) The same goes for the primary cover bolts, and make sure you criss cross them when you tighten it up.