NP203 only operational in lo-loc and hi-loc
 

Ive been searching and Im not coming up with anyone having the same trouble Im having.

My rig is a 78 K5 350/350 lifted 8" on 35" Gumbo Mudders. It has 3/4 ton d44 up front and GM corporate 14bff in the rear. The NP203 transfer case apparently has the part time conversion kit in it because the danna 44 has lockout hubs already installed.

What will cause the t-case to only power the K5 in lo-loc and hi-loc? Is there something they previous owner could have missed or done wrong when doing the part time conversion? And also, how do I tell if they actually did the internal conversion or just simply installed the Warn lockout hubs? Thanks in advance and sorry if I missed this topic in my search efforts. Nick

From the sounds of it, the previous owner did not do a part time kit. Lock in the hubs and see if it moves in LO & HI. If it does, then the transfer case is stock.

Thanks a million, locking the hubs in did the trick. Believe it or not, I am actually mechanically inclined and even worked as an assembler in a truck manufacturing plant. I just completely overlooked this possibility assuming that the previous owner would have converted the np203 while going through the trouble of upgrading the front and rear differentials. The lockout hubs must have already been on the 3/4 ton axle when they put it in.

Now, Im wondering about running with the hubs locked in all the time. Ive always heard (and practiced) that you shouldnt leave your hubs locked in while the transfer case is not in 4 wheel drive. I realize that this is a full time 4 wheel drive transfer case, but while in H or L it doesnt actually power the front diff all the time. So will this hurt anything to run it with the hubs locked in for a while until I do something different (part time conversion or swap t-cases)?

All NP203 equiped vehicles were originally supplied with a splined 'puck' at each end of the front axle with a dust cover to close things up. So running with the hubs locked is just putting things back to how things were originally. You may notice a drop in fuel mileage, but with these trucks... You can do the part time conversion or swap t-cases, which ever you prefer. Hang onto that NP203 though (search "np203+np205+doubler" in google).

I have a 3/4 ton 10-bolt that I am stealing the hubs/brakes/spindles out of to swap over to my D44 when I drop in my 14BFF. It came out of a truck originally equiped with an NP203. I'll be keeping those caps & the 'pucks' as they are good backups on the trail.

Sounds like youre building a tank. Ive always been a fan of the 70s model Chevy trucks and Blazers. I just got this chance to trade my 87 S-10 Blazer 4x4 with the 2.8 V6 backed by a 5 speed, for this 78 K5. I cant wait to take this big guy out on the trails and dump it some holes we play in. Ill check out that 203+205 doubler you told me about. Thanks again.

I have a 79 with an automatic and a previous owner installed locking hubs instead of leaving it in full time all wheel drive. This confuses me. Why would someone do this? What are the advantages besides better gas mileage?

Without doing the part time conversion, nothing is really gained by putting lockout hubs on the front. With the part time conversion, nothing in the front drivetrain spins when in LO or HI with the hubs unlocked. This decreases the rotating mass and can increase mileage.

But even with the part time conversion, you need to drive it in a LOC position for a bit to get oil thrown around inside the transfer case to keep the rear output bearings lubricated.

I have no idea if I have the conversion or not. Not really mechanically inclined and new to the Blazer game. However with hubs locked my Blazer runs in all modes.

This is the same as my 78, except they had swapped in 3/4 differentials. But now its all taken care of thanks to swartlkk. Keep em locked in and hammer down. lol

Not sure if I am missing something, but whether I have the part-time conversion or not, just keep the hubs locked 24/7 whether driving in hi or hi-loc since it is an automatic?