203 Trans case question

[Cheyenne75]

I searched here first sounds historic but though I would ask again since it was a post from 2002 and more experts have fixed this buy now..


1975 K5 trans case does not want to stay in H and pops out or just won't engage. Works well in all other positions and I'm driving in H-LOC..what's the app that may fix this?.

Also will a NP205 fit my 75 and how do you fellas rate it vs 203 not sure on all the mix matching of car parts..sorry there but thanks for the site and all the experts

 

[diesel4me]

I'm not an expert ,but it might be the linkage just needs adjusting (if your truck has a body lift that is likely)--or it can be an internal problem too,like a shift detent rail & ball being worn ,excess end play in one of the shafts that the gears ride on,etc..

I put a NP205 in my 74 GMC that came with a NP203 (because it had issues like yours and a very sloppy chain inside that "jumped" if you took off too quick)--I had to use the tranny to t-case adapter that goes to a NP-205 that was on it when I bought it,(your NP-203 one wont work) --my truck had a TH350 tranny,it bolted up OK to the crossmember mount and the tranny,but the front driveshaft was now too long,and I had to find a shorter one..the rear one fit fine though...I think I had to cut a bit of the tunnel away too ,for the shifter to not hit,but my truck had a body lift and that may not need doing in your particular instance...

 

[onetonbb74]

do you have front hubs that lock and unlock? If you do, and there unlocked, the regular Hi and Lo positions will not work and you have to put it in Hi-loc and Lo Loc to move the truck.

 

[Cheyenne75]

Thanks Diesel kinda thought a adjustment but just needed a little more input. It's all stock it was a barn find no lift thanks for the extras I need to do and get when I replace the 203..thanks a lot again.


No the hubs are full time all stock 1975..now what do I need to buy

 

[diesel4me]

The trucks that came factory with NP-203 t-cases had no hubs,being "full time" 4wd...they used a "slug" (drive gear) without any provisions to lock or unlock,there was just a hub cap over the hub where locking hubs normally go..

You will need a NP-205 from another truck and the correct adapter to mate it to your tranny,and the side mount that attaches to the frame (you may be able to use the one off the NP-203 if it had one,they are very similar--some had a torque bar from the t-case to the bellhousing bolt or none at all,depending on what year and tranny it used)..

You'll need to determine if you have a TH350 or TH400 tranny ,the bolt patterns and spline count on the output shafts differ and the transfer cases have to have the correct input to mate them up...your original crossmember "should" work ok,you will also need the shifter for the t-case and maybe the little gear box that goes between the transfer case and speedometer cable too,to get accurate speedo readings..then you might need driveshaft mods if they end up being the wrong length...

It would be best to have a complete "donor" truck to pick all the parts from,it'll be a lot simpler that way and you'll see how everything should be assembled before removing the parts..

It could be your Np-203 had a "part time" kit installed ,and something in it failed,I remember some of the cheap kits sold in the 70's that would allow it to be a true 2wd to increse fuel mileage,used crap powdered metal gears in the differential inside the case,instead of good quality steel,and if one failed,it wouldn't move unless you put it in the "lock" position in either 2wd or 4wd..a lot of guys used to run them with no front driveshaft and in the lock position,due to way too high lift kits ,and that stressed the t-case beyond its limits and it would eventually fail...