I have a problem with a d-15 allis transmission - in third gear, the reverse idler gear hits the reverse gear and third gears.
the trans was pulled down origionally to replace third gear, because it jumped out of third gear. i replaced 3rd gear with a new gear, and reverse gear with a good used gear, which solved the third gear shifting problem. it doesn't appear that there is enough room between the third gear and the reverse gears for the idler gear (which is where it rides at rest). I scrapped the old gears, so i can't compare the new to the old.
I just have an I&T manual to go by, and the info in there isn't great.
if you think you can help, email me. i would greatly appreciate it.