transfer case swap help

[ncguy89]

ok guys please bare with me as im going to try to keep this as simple as possiable. ok to start with i have a 84 chevy k10 with a th350 and np203 setup with part time conversion. my transmission went out on me and im getting it rebuilt. the 203 has a broke output shaft so i have a brand new np208 sittin in my building that came out from behind a th400. i got it with a parts truck that i put maybe 500 miles on. now these are my questions! what output shaft do i need to put in my th350 to use this np208? do i need to move my tcase crossmember and do i need a different drive shaft (also has the front driveshaft still bolted on it)? thanks alot for any help provided.

[ncguy89]

and btw the 350.203 combo was swapped in by previous owner, its not orignal.

[thirsty]

I can't answer all of your questions but know the answer to at least one. You need a th350 to np208 adapter to use the two together. They are hard to find because not many trucks came with that combo. I'm not sure which transmissions have the same splines. I do know for sure that a 208 that was behind a th350 will not work with a sm465 (I thought they were the same spline and hung onto one for about 4 years then realized I was wrong while installing it ). So before you go to far make sure everything you need is available to you.

[ncguy89]

i do know i will have to change output shafts i just dont know what output shaft to use in the th350. i know it needs to be 32 splines. are these adapters available through advanced adapters?

[ncguy89]

i actually just found one on advance adapters websight. everything im reading is for a 2wd th350 but mine is a 4wd th350 so im guessing i need a certain output shaft?

[thirsty]

are these adapters available through advanced adapters?

Not sure about that. I would look for an 81 truck or blazer to get the real thing first. I'm not sure how long GM used the th350 after 81 if at all before they went to the 700. Somebody here will chime in that knows for sure. I know that in 81 when they started using the 208 the th350 was still an option.

[ncguy89]

nvm about using the th400 adapter i know i cant use it. i just have to find a adapter for the th350 to np208 now.

[ncguy89]

im guessing this is the adapter i need? http://www.ebay.com/itm/TH700R4-TH350-NP208-NP241-Short-Adapter-Plate-Chevy-GMC-Truck-4x4-15597796-/290685586588?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26otn%3D5%26pmod%3D290621217018%26ps%3D63%26clkid%3D7791226549073729561

[thirsty]

Here is a link I found for you that might help you out.
http://67-72chevytrucks.com/vboard/showthread.php?t=323994

[ncguy89]

great article, the more i read the more i see imma have to spend about $400 on a adapter kit to make this work which is more money than i have to spend right now. i have figured out i need a adapter. now my quiestion is what 32 spline output shaft do i need for my th350 to work with my np208?

[Irish_Alley]

imo i would look for a used 203 off a th350 and be done with it use it for parts or swap out the whole thing it will be a whole lot cheaper than buying a custom shaft then buying a new front and rear driveshaft. might even be able to find a th350

[Blazin]

208s were only used behind TH350s for 81, and 82. The adaptors are hard to find, but are still out there.
 Thanks to Thirsty I have one that's not broke in half in my Blazer!
 
The output shaft of a TH350 that was bolted to a 203 is to short if I remember correctly from years ago when I tried to put one in my 81 Blazer.
I put a short tail shaft 2 wheel drive TH350 in it. I had to cut about 34/" to an 1" off the output shaft to use it with a 208. If you get an output shaft for one of them, and shorten it you should be in business.
I came to the amount needed to be cut off by sliding the 208 on the back of the TH350 until it bottomed out. Measured the distance between the two housings, and gave it an 1/8" Stuffed a rag in the back of the trans, and cut it off with an air wizzer while my girlfriend held a magnet real close so as not to get a bunch of metal shavings into the trans. Used a file to bevel the end.
SM465 and TH400 have if I remember correctly 28 spline output shaft. 700r4s, and TH350s have I think 32 spline output shafts.
 

[Psycho71]

For the money, wouldn't it be worth looking into getting aa th400 transmission? It would bolt right up, and is inherently stronger than a th350 anyway. I had my trans guy do a complete rebuild on my th400, with converter, for $450. Food for thought.

[bake74]

For the money, wouldn't it be worth looking into getting aa th400 transmission? It would bolt right up, and is inherently stronger than a th350 anyway. I had my trans guy do a complete rebuild on my th400, with converter, for $450. Food for thought.

     I think he was trying to use what he had laying around without spending a lot of money.

[ncguy89]

i was but instead of rebuilding the th350 i went ahead and called the trans guy and am having him to build me a th400 and i will just take him my core with a 32 spline output since thats what the tcase has. only gonna cost me $80 more and i know it will work since thats what trans the tcase came off of!!! thanks for all the help guys!!! and just for everybody to know if you dont already im getting my trans done by cooks racing in cowpens sc. th400 rebuilt out the door is running me $380 with core. heck of a deal and awsome warranty.