# 203 fulltime



## hardycad (Oct 25, 2001)

i have a 80 chev shortbox yes with a 203 fulltime ftansfer case and manual hubs . will this hurt me driving with the hub's locked in i plan on getting the partime kit but not for a while and what do all the lo lock lo hi hi lock mean . and why does my transmission grind when putting in park some times. lot's of little prob's but just like to know the answers. thanks to any body who can help


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## MTCK (Feb 13, 2000)

Driving with the hubs in won't hurt it. That's how they came, without selectable hubs, they were just always in. On the shifter, when it says Loc, it's talking about the center differential in the transfer case. Like a normal part time 4x4. Use then only when off road or in snow, ect. The others leave the diff open. As for the tranny, I dunno about that. Stopped all the way before you throw it in?

MT


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## hardycad (Oct 25, 2001)

> _Originally posted by MTCK _
> *Driving with the hubs in won't hurt it. That's how they came, without selectable hubs, they were just always in. On the shifter, when it says Loc, it's talking about the center differential in the transfer case. Like a normal part time 4x4. Use then only when off road or in snow, ect. The others leave the diff open. As for the tranny, I dunno about that. Stopped all the way before you throw it in?
> 
> MT *


tthe truck only grinds the tranny when it is in neutral and i try to move the tranny into the 4x4 gears or the tranny from drive to park


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## MTCK (Feb 13, 2000)

I'm not sure that I follow. It grinds when you have the transfer case (4wd) shifter in neutran and select a gear with the transmission? When switching the transfer case between high and low range (at least with my 208 model case) you need to be stopped, and have the transmission in neutral. Otherwise it will grind. If it's grinding with the transfer case in neutral, why do you have it in neutral? The only time I've ever heard of people leaving it in neutral is when they are flat towing, or went to a party and didn't want to be able to drive home..... If you tell me more specifically when it's grinding, where both shifters are, and what you're doing, maybe I can get in this a little deeper.

MT


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## Chuck Smith (Dec 30, 1999)

A few things don't "jive" here. First of all, in 1980, GM used the NP 205 in all trucks. I am not saying it's impossible that you have an NP 203, just not likely. Let me explain more. As others have said, when a truck has the NP 203 transfer case, it doesn't have locking hubs, it has solid gears connecting the wheel hubs to the drive axles. The NP 203 as others have said, has an internal differential. As others have said, when you move the t case shifter to either of the Loc positions, it locks the internal differential, distributing power to the front and rear axle equally.

Now, if you installed locking hubs, and didn't install the part time conversion kit, the only way the truck would move with engine power, is if you had the t case in one of the lock positions, or if you had the hubs locked in. The internal differential is an "open" differential. That means if you didn't convert the t case, and left the hubs unlcked, all the power from the t case would go to the front wheels. Since the hubs aren't locked, the truck wouldn't move.

I learned this the hard way with my 77 Chevy when I first got it. I jacked up one of the front wheels when I was going to replace the front brake pads. The truck was in park. As soon as the wheel came off the ground, the truck started rolling down my driveway on 3 wheels and the jack. Luckily, I was able to drop the jack, and stop it before it got too far. I put the t case in Hi Loc, and jacked it up with no problems.

Also, the NP 203 can be shifted into the HI Loc position at speeds up to 55 MPH (so says the decal on the sunvisor, not that I recommend doing it at such a high speed) because it has the internal differential.

When you convert the NP 203 to part time, the kit comes with a solid gear to replace the internal differential in the t case. You then end up with an "extra" gear. The position on the shifter floor plate marked "Hi" becomes 2wd Hi. The position marked Lo, becomes 2wd LO. That is the extra gear you get, 2wd Lo.

These facts are why it doesn't make sense that you have the NP 203. Again, I am not saying it is impossible, just that the facts seem to indicate otherwise.

As far as the grinding, there is a way to ensure the NP 203 shifter is adjusted properly, which could be the cause. However, it is too difficult to expalin without the diagram in the GM Factory Service Manual. I need to scan it in, and I can't use my scanner with this computer.

As far as driving with the hubs locked all the time, depending on the quality of the hubs, they may not hold up for long driving on dry pavement. There is a lot more resistence driving on dry pavement under power than there is driving in mud, snow, wet pavement, etc.

~Chuck


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## Chuck Smith (Dec 30, 1999)

*NP 203 Shifter Adjustment*

I wasn't sure if I had the diagram on my server or not. I checked, and I do. You can see how to adjust the NP 203 shifter here:

http://www.chuckschevytruckpages.com/images/203shiftdiagram.jpg

~Chuck


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## DaveK (Jul 9, 2001)

> and left the hubs unlcked, all the power from the t case would go to the front wheels. Since the hubs aren't locked, the truck wouldn't move.


 And since the drivetrain IS moving..... putting it in park, would cause some "grinding" noise. 
Probably all the grinding noise is because you are shifting the Tcase or putting it in park when the front hubs are unlocked and the drive train is moving. Kind of like shifting or putting it in park when driving down the road.


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## hardycad (Oct 25, 2001)

*203*



> _Originally posted by Chuck Smith _
> *A few things don't "jive" here. First of all, in 1980, GM used the NP 205 in all trucks. I am not saying it's impossible that you have an NP 203, just not likely. Let me explain more. As others have said, when a truck has the NP 203 transfer case, it doesn't have locking hubs, it has solid gears connecting the wheel hubs to the drive axles. The NP 203 as others have said, has an internal differential. As others have said, when you move the t case shifter to either of the Loc positions, it locks the internal differential, distributing power to the front and rear axle equally.
> 
> Now, if you installed locking hubs, and didn't install the part time conversion kit, the only way the truck would move with engine power, is if you had the t case in one of the lock positions, or if you had the hubs locked in. The internal differential is an "open" differential. That means if you didn't convert the t case, and left the hubs unlcked, all the power from the t case would go to the front wheels. Since the hubs aren't locked, the truck wouldn't move.
> ...


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