Stripped threads on TH350 transmission

[BrianG]

When I took my transfer case away from my transmission I though it was odd that it had three studs and one bolt. There was a bolt in the lower left hand spot if you are looking at it from behind. This is right next to the (sorry for sounding like a complete idiot, but I am with transmissions) round cover in the back... the modulator maybe??

So anyhow, when I went to put it all back together today, that bolt would not tighten up. It almost did, but never really got tight. Tried putting a stud in, but just wound up with what was left of the threads on my stud.

My question is... Can I just run a tap in that hole to the next size larger bolt, or will I end up with shavings where I don't want them. I can't tell if that hole is open to anything inside the transmission. I know that it is not open to the area right next to it where it mates to the transfer case adapter.

What are my options here besides a complete tear down?