Author Topic: NP203 w/Manual Hubs...questions  (Read 8507 times)

Offline jharness74

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NP203 w/Manual Hubs...questions
« on: August 02, 2002, 09:17:00 AM »
I'm looking at a '78 Chevy Suburban and it has the NP203 transfer case with manual locking hubs. I assume since the NP203 is a full-time case that the transfer case is always engaged and the front drive shaft and axles are always powered. So, with the hubs unlocked the front wheels are free from the axles, but everything is still powered by the transfer case...is that right? If so, then what is the advantage of having the locking hubs? I assume with the fronts unlocked that you will probably have a better turning radius and get longer tread life from your tires, but that's just my guess. Is this something that alot of people with the NP203 have done, or was there actually an option to have the NP203 with locking hubs from the factory?

Also, this would be my first 4WD, so where do you check your fluid level for the transfer case? Is there just an extra dipstick? I've read some other posts about transfer case maintenance and they say to use 10w40 in a NP203. If there is something else in there (tranny fluid or gear oil), should this be a cause for concern? The guy who has it doesn't seem to have alot of mechanical know-how, so he may not even know what is in it. He's had the 'Burb a couple of years but never really used it.

Thanks for any info.

Jason Harness
'74 GMC C2500 Camper Special 454/TH400/4.10  


Offline oscarone

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t-case
« Reply #1 on: August 03, 2002, 03:46:00 PM »
If the axles have manual hubs the case should have a part time conversion.  Do this (slow please) with the hubs "unlocked", drive the truck and, hanging out the door, watch the front output shaft.  It should not turn.  If it does someone has put the hubs on without the conversion.  This would mean the case has been driving the axle and not the wheels.  This could be bad.  If so, I would pull the dif.  cover and check the gears.  Chevy/GM did not offer manual hubs with the 203 case, as, it was full time.  The purpose of the conversion is to save driveline wear.  Installing the conversion allows the case to "act" like a part time case.  It will have no effect on your turn radius.  If the truck is stock height your turn radius should be ok.  If it has been lifted (suspension, not body)  than the radius is probley cut down a little.  The correction for this is a later topic.  
To check the fluid level...there is a square plug on the back of the case...just above and to the right of the output shaft.  Pull the plug...if oil comes out your ok.  If something besides oil comes out, change it!  The 203 should be serviced with nothing but 10W-40!  If you need to drain it, pull a couple of bolts from the bottom of the case.  When re-installing the bolts seal them with some rtv.


Offline 79GMC4x4

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Re: t-case
« Reply #2 on: August 07, 2002, 10:40:00 AM »
I have been there, and done what Oscar says to do, but if you have a second person, have them watch for the driveshaft's movement.  

'79 GMC shortbed 454 th400 14 bolt FF NP205 Dana 60


ehjorten

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t-case
« Reply #3 on: October 31, 2002, 02:15:00 PM »
test...


ehjorten

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Re: t-case
« Reply #4 on: October 31, 2002, 02:25:00 PM »
If you have manual locking hubs and you don't have the transfer-case conversion...you will probably not go anywhere, depending on the condition of your differentials.  Without the conversion the truck will try to drive through the driveshaft that has the least resistance...the front!  The conversion takes the center differential out of the system.  The NP203 has a tendency to stretch the drive chain and it sounds like your u-joints are going out (clang-clang when you are getting on and off the throttle).  One thing that many people don't know about the converted NP203's is that the rear bearings rely on splash oiling from the action of the full-time transfer case.  With it converted you should drive the truck around with the hubs locked every few hundred miles to re-oil the rear bearings.  In fact...you can drive around in 2wd with the hubs locked in poor traction conditions and then just put the t-case into 4wd on the fly (say...if you are heading to the snow...you don't have to stop and turn the hubs in)!