NP203 problems with 4H on part time kit
 

Hi all, new to the forum. I've been putting a 78 3/4ton K20 back together and have an unusual problem i can't seem to find anywhere on this forum. I have an NP203 transfer case with the part time kit, TH400 transmission, and a SBC 350. I know it has the part time kit because the hubs are locking and when i put it in 2wd Low i can turn the front drive shaft with the hubs unlocked and the same when i put it in 2H (used to be 4H without the part time kit). My problem is, in 2wd Low the truck does what its supposed to do, drives down the road with the hubs unlocked and locked, all be it at higher RPM's due to low gear, it also works well in 4wd Low, but when i put it in 2wd High, it bogs the motor down and dies when put under a load. Any ideas what could be causing this?

Re: NP203 problems with 4H on part time kit
 

Hi ,and Welcome,my 203 is changed as well
not sure about your issue but when it's converted it needs to be lubed up by running in 4X4.
I do it hubs unlocked a mile or two,move the shifter,so far so good!
and yes it will go 4X2 in low,but you don't want to run the front engaged on pavement or it will bind up.
I did use the front alone one time ,rear drive shaft was out,replaceing ujoints
dam hope nothings broke on ya

Re: NP203 problems with 4H on part time kit
 

I understand what needs to be done on a converted np203 to keep it oiled, my problem is i bought the truck without a transmission, installed the th400 and the np203 and i haven't been able to get it to run right yet lol. It appears to work fine in all gears except 4High (2wd). I'm not sure if the previous owner burnt it up by never running it in 4x4 or what. If the chain was broke, wouldn't it not turn the front driveshaft? Maybe it has the cheap part time kit with the wedges instead of the shaft and its worn out causing it not to work?

Everything i've done to the truck so far:
Brand new TH400 installed with torque converter.
Fresh oil in transfer case.
Fresh oil in engine.
New valve guide seals.
New Distributor, cap, rotor, coil, plugs and wires.
Total timing set to 36* at 2500 RPM.
Adjusted rockers with engine running, 1/2 turn past 0 lash.
New edelbrock 600cfm carburetor 1408.
New fuel pump.
New alternator.
Fresh gaskets on edelbrock intake manifold (as it wasn't on when i got the truck)
4wheel complete brake job, new master cylinder and all.

Fuel delivery problems, running sluggish
 

Welp, i feel like a dumb a** now. Put a fuel pressure gage on and noticed it was erratic between 3 psi and 8 psi. Thought what the hell and bypassed the tank and threw in a 2 gallon gas can straight to the fuel pump. Held a solid 8.5 psi with no needle jumping and held above 6 psi through RPM range. Truck runs way better but its still not at 100%. It no longer wants to die when i give it full throttle but i still feel as though its not getting enough fuel (now that i know that was the problem). My fuel pump has a return line, my rear tank is leaking and i need to replace the lines anyway. Can i get an earlier tank with a feed line only? and install a single in single out fuel pump?

Re: Fuel delivery problems, running sluggish
 

oh ,i'd stay 3 line,helps with vapour lock,my 78 is two line.79 is three.
it helps keep the fuel cooler
I was wondering gummed up transfer stick...
check this out "twin sticking a 203"
http://67-72chevytrucks.com/vboard/s...d.php?t=360447

Re: NP203 problems with 4H on part time kit
 

I dont believe its the transfer case being burnt up the one in mine is and it wont allow me to get into low unless I am rolling (I mean it wont. foot on shifter bumping trans it into gear it aint happening) but going into high is just like it should be I do have twin sticks in my truck though so the shifter doesn't bind.