From what I understand (and I have been known to be wrong once) BD bought all kinds of trans parts and mixed and matched them as they wanted to or had parts for. I do know that if Baker or Jims built the trans they would have good bearings in them and not the junk BD put in them and good main shafts.
Why in the world BD would do this and not just buy trans from Jims or Baker with a warranty is beyond me. Maybe that's why they went out of business. (too many repairs)
3 weeks after putting on a 3.5 belt drive my trans is leaking oil. I have the outer bearings too on the belt drive so I guess the trans bearing is wearing and the seal has taken a beating. I have a Jims case and Lord knows what is inside.