NP203 problems

Hey guys Im hoping you can help. I have a 1978 chev 3/4 ton 4x4 plow truck with a TH400. The Np203 transfer case is jumping and skipping so bad I cant plow anymore with it. I have a NP205 from a '78 three speed. I also have the option of putting in a TH350 with another NP205 from a junked 1/2 ton. Will either option be feasible with existing driveshafts from either truck and hardware? Thanks in advance for any insight.

Welcome to AF. I've never swapped out a 203 for a 205, but here are my thoughts on that.

If you do it why change the tranny? I think there are t-case adapters available to match up the 205 to the TH400.

Drive shafts I'm not sure about but they sould be easy to measure to see if they will work with the 205.

If you have the "full time" front hubs you'll need to replace those with manual ones.

I'm sure you know this but! If you're in hi 'lock" or low "lock" it's going to hop around in tight turns. In regular hi or low the hopping should be very minimal.

Have you checked fluid level and/or changed it lately?

My '78 K5 Blazer has the 203 system and works great. Best thing about it is I don't have to get out and change the front hubs.

Hope this helps and once again just my thoughts.

I know about the jumping and lurching while turning. This one works alright until I start to work it, like pushing snow. I just bought the truck and now my wife says I must have sucker written on my forehead. So I'm trying to fix it ACAP (as cheap as possible) to keep her quiet. I did pop off the side cover and the fluid was pretty dirty. It smelled like gear lube but if I'm not mistaken it should be 30W oil. As for the adaptor plate, I don't fully understand how they work. Since the output shaft on a TH400 is larger with more splines than a TH350. In order to save my pride and not admit to my wife she was right, I would appreciate any "cheap" ideas. Thanks

The 203's use gear lube.

Best of luck to you with the wife.