Actually all you need to convert a TH from two wheel to four wheel is the appropriate output shaft for your T-case and the appropriate T-case adapter. I have done this many times since two wheel drive trans are cheaper to find. Beware of the combo you choose since some of the T-case adapters are getting rare and can get rather expensive. Years ago I converted a TH475 from 2wd to 4wd drive for my fullsize mudder. Took about four hours with the prerequiite beer breaks. Any good tranny book will help you figure it out.You need to change the mainshaft too in addition to what was posted above. Its not worth it. Remember you need to put a manual valve body or a mechanical modulator in it too.
I beg to differ on that one. I've had a NP208 in my 84 fullsize K30 for quite a few years now. It does see some moderate of road use like getting fire wood and the occasional juant through whatever to pull my friends out. My buddy has one in a fullsize blazer that gets the living crap beat out of it everytime it goes out.The 208 is a pile of junk. They're far more expensive than a 205 seeing as they all break and everyone who needs one pays for it.
It's a bad design that's prone to case and shift fork failure.
Is there any possibility that you could find out where the bolt on NP205 application to the 2WD transmission was originally installed? Do you have a casting number available for the NP205 input housing? Probably a 3/4 or 1 Ton but in what what year range?There are some NP-205s that will bolt right up to a 2 wheel drive TH-400 tranny. I just bought a TH-475 last week that came from behind a 4bt and my 205 case bolted right up to it after removing the bolt on yoke and snout from the trans.
They are not as easy to find as the other 2 versions of 32 spline 205s, but I have had several in the past. Another option is to buy the adapter and a special 27 spline output shaft to go in your 400, this will mate your 400 with a much easier to find TH-350 version 205 case