1976 K20 NP203 HELP! So confused!

Thanks for taking the time to read this post! This will be a mouthful. Np203 with manual locking hubs, I have done so much research here on the forums and calling around and have gotten nowhere. Recieved the truck in Low LOCK. Got it running and have done everything thusfar in this mode, hubs UNLOCKED.

1. Will only drive in Low LOCK, and High LOCK with hubs unlocked OR locked, doesn't seem to matter.
2. Grinds like hell in High or Low if trying to go into Park on Tranny.
3. With Trans in N, front shaft will still spin by hand with truck not running?
4. When Trans in N, and placed into High, then Drive, truck will not drive (hubs locked or unlocked) but front shaft starts spinning like a PTO while in drive!
5. Case was low on oil, so oiled it, cleaned linkages and did a linkage adjustment, even though it didn't seem needed.
6. Inside arm on 203 wiggles around side to side loosey goosey but operating the shifter still moves arms where I (think) they need to be.
7. This tells me there is no part-time kit installed, but could the differential inside the case be toasted?

Any info helps guys, I'm pretty bummed.

Sounds like it's a problem in the front axle, whether it be something broken internal, a broken axle shaft, or a hub that is not actually locking in when you turn the knob. If the front drive shaft is turning, something else should have movement too. So when you rotate the shaft, look for the u-joints at each wheel to move. If one moves, lock that hub and rotate the shaft again and see if the other u-joint moves. If it does, then lock that hub too. At that point, you should not be able to turn the shaft.

If a u-joint rotates when that hub is locked, it's an issue with the lock or the stub shaft.

If neither of the u-joints rotate when you turn the drive shaft, something is blown in the pumpkin or an inner axle shaft is broken.

Depending on what is actually wrong, there may be a couple more steps to get it figured out. Just keep in mind that with an open differential, a failure of any kind on either side will make it so that the opposite side will not receive any drive power.

Also, it does sound like your 203 has not had a part-time conversion.

Take one variable out of your troubleshooting - lock the front hubs and verify each axle u joint turns when you rotate each wheel, since a factory NP203 truck would have had fixed hubs.

Then run through each transfer case position and see how it works to turn the driveshafts.

I think you might have an NP203 with a broken part time kit - but I have no experience with how they break.

#4 is the key. The front shaft spinning while in drive and the hubs locked but the truck does not move. No matter what could be wrong with the t-case, #4 says there's a problem with the front axle.

I will try this tonight again and report back, thanks for the replies! Last time I was under there with the hubs locked, when I spin the front shaft, the U joints at the wheel spin as well. Hopefully all of this is due to the hubs. But like I said, I will re-verify this after work.

Ok. So regardless of locked or unlocked, with 203 in H. I can spin that front shaft by hand and the wheel U Joints turn.


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Maybe someone didn't assemble the axle lockout hubs properly- or they are missing parts in them.

In your above post when you were turning the front driveshaft by hand were the front tires on the ground?

Yes tires on the ground. This weekend I’m going to jack the front and tear into the locking hubs and see if I can see anything that lets me know they’re junked or installed wrong. They are Warn brand. Look older.


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Jacked up truck. Took off those warm hubs and looking at the pieces, I’m unsure how they ever worked correctly. Doesn’t seem to me like they were engaging anything at all! It looks like there was a part never installed. I circled a part down below that these do not have. I didn’t pull axle shafts yet but spinning them by hand they feel good?


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I like this thread!
Keep goin....

Yeah, without those parts circled in yellow, it's just relying on hopes and dreams to drive the front wheels.

But hay, it's good to have hopes and dreams. Bucket ..stop bein mean .

Maybe you shouldn't listen to him new guy..I think he's an ass.

Ain't nobody gonna break it, your stride. Aint nobody gonna hold you down.
Oh no.
You got to keep on movin.














Wait.
























Oh no!

Stupid jukebox.

Well, there’s your problem.

Put drive flanges back on it.Simple,less parts to deal with.Probably be able to find the pieces in salvage yard.You’re gonna end up driving with the hubs locked all the time anyway.