NP 203

[77chevyshortbox]

Hi, I have a 77' GMC shortbox, I had bought it through a friend who owned the truck for a few years. When I had first bought the truck I was under the influence that it was a part time 4x4. But as I had the truck I had noticed problems with my drivetrain. When I drove the truck home my hubs had been unlocked, and the truck seemed to move fine.(oh yeah I have manual locking hubs, from super winch. the previous owner said they were already there.)Anyways, as I got the truck home a friend of mine I belive put the truck into 4hi, or so I thought. for the longest time I thought something was wrong with my truck. I changed the shifter on the transfercase and everything seem to work fine. All under the idea that the truck was still a part time 4x4. The truck once again moved with the hubs "free" except one time the linkage had jammed up, but I gave it a smack with my palm of my hand and everything was fine again. So finally I go to bring the truck home from my schools shop and I run into the same problem. except the Hubs were free and the shifter was in what I assumed was 4lo. when I pulled it back the truck woudlnt move unless the hubs were locked. but if the shifter was all the way to the dash the truck would move fine. Finally I started lookin around and realized I had a NP203, not a 205. Not being sure I checked the top of my shifter and it was the same handle. so what my problem is,the truck will only move if the hubs are locked. unless the shifter is all the way forward in what in presuming now is 4lo loc. is the a possibility I have a conversion kit? or is this a normal thing. 

thanks  Nick.

[Irish_Alley]

as from what i understand you don't have the kit installed the reason you cant move is cause your in unlock instead of lock if you pull the shifter all the way back towards the seat it should be in 4hi lock and your hub should be able to be unlocked and you still move. whats going on is almost like when you only spinning one wheel the power goes to the ones thats spinning with little resistance " the front shaft " with it in lock you have the same power going to the front and rear. its normal but you should be in 4 hi lock with the hubs unlocked and you should be fine but the front shaft will turn
the conversion kit is this i think
4 low lock
4 low unlock
2 wheel high
4 high lock

the 203 is w/o

4 low lock
4 low unlock
4 high unlock
4 high lock

[beastie_3]

as from what i understand you don't have the kit installed the reason you cant move is cause your in unlock instead of lock if you pull the shifter all the way back towards the seat it should be in 4hi lock and your hub should be able to be unlocked and you still move. whats going on is almost like when you only spinning one wheel the power goes to the ones thats spinning with little resistance " the front shaft " with it in lock you have the same power going to the front and rear. its normal but you should be in 4 hi lock with the hubs unlocked and you should be fine but the front shaft will turn
the conversion kit is this i think
4 low lock
4 low unlock
2 wheel high
4 high lock

the 203 is w/o

4 low lock
4 low unlock
4 high unlock
4 high lock

Correct.

[77chevyshortbox]

thanks guys. I wasn't really sure, I had read up alot of stuff and fooled around with it a bit but it makes sence. so basically the truck will run in 4lo loc or 4hi loc without the hubs locked, but the hubs should be locked in 4hi unlock and 4lo unlock? just wanna make sure I read that right. sorry if I'm coming off stupid or anything, I just wanna be sure. don't wanna run into any kinds of problems like this on the road and not be able to figure it out. thanks alot.

[beastie_3]

It doesnt sound like you have a transfer case conversion kit. If you can only move in 4low, then something is wrong. There is no reason to be driving the truck in any gear besides 4hi, regardless of the conversion kit or not. If the truck will only move with the hubs locked in 4hi, then you dont have the conversion kit, or something is broken. If that is the case, I would get the transfer case looked at or install the conversion kit.

[Captkaos]

Sounds like some just put locking hubs on it with no conversion, or they replaced either the transfercase with a none converted one or replace the axles with locking hubs.

[77chevyshortbox]

thanks alot for all the feedback. I'm pretty sure the 203 is bone stock, no conversion. after reading everything I have so far thats what I'm betting on. I talked to the guy i bought the truck from today and he said he's never even herd of a full time truck. soo that really goes to show that there is a good possibility it is, also I've herd rumor of people replacing the stock hubs with manual locking hubs, because of freezing in the winter with the automatic hubs, or even if they automatic hubs break it's easier to replace with manual. not to sure on all that but could be a possibility. thanks again tho.

[VileZambonie]

The full time trucks didn't come with auto locking hubs or manual locking hubs.

[77chevyshortbox]

alrite thanks. see im not to sure about how the fulltime system worked with the front hubs. ive got an idea just wasnt sure. any idea as to why theres manual locking hubs? because from what i can tell now the truck is full time 4x4. im assuming the previous owner before my buddy just threw them in there because?

[beastie_3]

I understood it better when I first learned about the 203's as I imagined it as an all wheel drive. When your in 4hi or 4low, there is a "limited slip" so to speak in the transfer case so you dont break anything when you turn (because each wheel turns at different speeds). Now when you put it in hi loc or low loc, imagine there is a spool in the transfer case and everything is locked. When you turn, which you dont want to on a hard surface, the front and back want to turn at the same speed. It might not be a good explanation, but thats how I understood it.

With the conversion kit, you now get 2wd hi instead of "all wheel drive". As for what happens when you put it in 4low, im not sure and dont care because I have no need for 4low. If im wheeling, its either hi loc or low loc. Just the terrain I drive in.


I have heard bad things could happen to the hubs if they are unlocked and the axle shafts are turning. Is that correct, I dont know and dont care because I wont drive that way. But if its true, you might want to keep them locked until you get that conversion kit.

[Irish_Alley]

i got the 203 in my truck with 38's with the kit or i think i do, with this snow i been driving with the front hubs locked 24/7 and only kept in in 2wd unless i needed to switch it over like for unplowed road or in a parking lot when i switch it over i just push in the clutch and pop it in place. now before the snow i would keep it in 2wd with the hubs unlocked, the reason i would think someone would put the locking hubs on i would think maybe to save money in gas so the front doesn't have to turn the tires just the shafts. also manuals are stronger. now the reason I'm not sure if i have the kit i was on my three wheeler one time and my dad was driving my truck we just came out of the woods and i was beside him and i saw my front drive shaft turning i could of bet i left it in 4 unlock and the hubs were unlocked so i don't know what was going on, if I'm under the truck and working on the shaft it has to be in lock for it not to turn

[77chevyshortbox]

yeah that makes sence. i've left the hubs locked since i found out it had a 203. before that i was under the impression the truck had a 205. now that i know otherwise i'll probably just leave the hubs locked. i gotta wait for it to warm up a bit so i can get my truck outside, my gates are frozen shut. one i do that i can look at it more try and drive it around to see whats all wrong with it. or if anything even is wrong with it. see alotta what ive read now makes sence and makes it seem like there wasnt a whole lot wrong in the begging. im not to sure tho. thanks alot tho.

[Captkaos]

any idea as to why theres manual locking hubs?

Sounds like some just put locking hubs on it with no conversion, or they replaced either the transfercase with a none converted one or replace the axles with locking hubs.

Running it with the hubs unlocked without the conversion is defeating the purpose of 4x4 as you have already found.
Running them unlocked with the conversion is not a problem.  BUT you need to lock them occasionally (say, twice a month) as the front unit gets oiled by the front shaft spinning.

[77chevyshortbox]

so just keep the hubs locked and i shouldnt have any trouble basically. and if i do then theres something wrong with the tcase?

[Captkaos]

Correct.