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73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Transfer Cases and Front Drivelines => Topic started by: 78k10cd on January 18, 2004, 09:54:00 PM

Title: NP203 shift pattern
Post by: 78k10cd on January 18, 2004, 09:54:00 PM
Hello everyone. I'm new to this board and 4x4s as well. I just picked up a 78 K10 short bed custom deluxe and was wondering about the transfercases. I'm pretty sure it's an NP203 since it has only a fill plug and no 3 bolt cover. I read somewhere that the speedo cable should be on the driverside, but mine is on the passenger side.

I also, wanted to know the shift pattern for it. I think it has the wrong shift knob. What should it look like, the one with 4 wheels or with the letters going up and down?

Lastly, what is this conversion kit that everyone is talking about for the NP203 and how do I know if I have it. I appreciate any help and sorry for all the questions. Thanks!

Title: NP203 Shift Pattern
Post by: 77 Stepside Morph on January 19, 2004, 06:13:00 AM
Here is a start on identifying your case....

darkwing.uoregon.edu/~jri...ubler.html

John

Title: .
Post by: 78k10cd on January 19, 2004, 11:59:00 AM
thanks for the link. I'm pretty sure it's a NP203 now.

Any help on the shift pattern/knob and the conversion kit? I'm really interested in converting to part time. thanks again!

Title: re
Post by: aprice on January 19, 2004, 07:34:00 PM
Well to know if it already has the conversion kit you would have the lock outs in the front if not then its full time. i've never done it but also of you havent noticed everyone recomends to lock the the lock out once a week or so to lube the tail shaft of the t-case

the pattern should be

(front)
low loc
low
nutural
high
high loc
(seat)

Title: .
Post by: 78k10cd on January 22, 2004, 02:29:00 PM
thanks aprice! i went to a 4wheel shop and they told me it's a np203 and that if you have locking hubs, its already been converted, which they do. He also told me that I have the wrong shift knob of the np205, and that mine is:

(front)
4L
2L
N
2H
4H
(back)

He said I should be in 2H for regular driving, but it really matters only when you lock up the hubs. Can anyone explain to me what each position is for? Sorry for the newbie questions, again, it's my first 4x4. Thanks!

btw, anyone know a place where i can get a new shift knob for the np203?

Title: Re: .
Post by: oscarone on January 22, 2004, 07:32:00 PM
Let's start this with an np203 with no conversion.  It is a full time transfer case...that is, of course, all four wheels receive power at all times.  The shift pattern for this is:

(front)
Low Loc
Low
N
HI
Hi Loc

With this Hi is your normal driving position.  All four tires are driven, but, the front and rear axles are driven independent from each other.  They are free to turn at what ever speed.  This is done thru a differential in the transfer case like the one in your axle.  If you shift to Hi Loc you are still in Hi range, but, the front and back axles are now locked together and turn at the same speed.  Again, the same way a locker works on an axle.  The Lo and Lo Loc works the same way only using a lower range gear in the transfer case.

Now..part time conversion...There are a couple of conversion kits out there and I'm not sure which you have, so, I won't get into that.  The end result is the same with all of them.  The first thing is the locking hubs.  You are now able to disconnect your front axle from the wheel.  This prevents the wheel from "driving" the axle.  Now your shift pattern has changed...but, not much:

(front)
Lo Loc
Lo
N
2 HI
HI Loc

The only difference is the HI Loc has become 2 HI.  The differential in the transfer case has been"disconnected" so it will not drive the front axle.  And this is your normal driving position.

Make sense?
The Np203 shift knob dosn't have the shift pattern on it (at least mine doesn't).  The pattern was on a plate that mounted to the floorboard next to the shift lever.  You can try  competitor.com or classicindustries.com for both...

I'll keep my eyes open for them...I'll be looking at some stuff myself tonight.

Title: .
Post by: 78k10cd on January 23, 2004, 06:46:00 PM
thanks for all the info oscarone! i'm still a little confused. so, what he told me is incorrect. are the 4-and 2- designations even correct? are the topmost and bottommost positions when all 4 wheels are driven. sorry, i'm kind of slow on all of this. From your diagrams, the only thing that changed is the HI to 2HI, which i'm assuming is still for street driving.

i have no idea what kind of converstion i got, but I have B&M hubs. thanks for looking out for the shiftknob. just let me know. if you want to email me, you can @ wvicente@sbcglobal.net, so that we don't bore the rest on stuff they probably already know. thanks again!

Title: NP203 Shift Pattern
Post by: 77 Stepside Morph on January 23, 2004, 11:02:00 PM
Although it doesn't make any sense,  my truck has manual locking hubs on the front, NP203 Case,  but is still fulltime 4WD.  It does not have the conversion inside the case to make it part time.  I only bring this up so that you know that the presence of manual hubs does not necessarily mean that you have the conversion in the case....  Please don't ask me why the PO did this,  because he didn't have a good explanation for me.

Thank you for the lesson oscarone...  I learned a lot about my driveline from this thread....

John

Title: Re: NP203 Shift Pattern
Post by: oscarone on January 24, 2004, 12:31:00 AM
Hmmm...that's a good point.  I don't know why anyone would convert the hubs, but, not the t-case.  The t-case conversion is pretty cheap really, and, easy to install.  But, good thing you brought that up.  I guess the best way to tell would be to put the hubs in "free"...t-case in "hi" and try to spin the front drive shaft by hand.  It should spin.  What do you think?

Title: Re: NP203 shift pattern
Post by: tfdrooke24 on November 05, 2009, 10:00:58 PM
Hello all,

Well I'm glad I'm not the only person out there not really understanding this whole np203 conversion.  I have recently (this week) purchased a 1979 C10 with the np203 behind a 350/350.  I am guessing that the conversion kit has been put in this transfer case because: One, it does have the manual locking hubs up front and Two, I can turn the front drive shaft with the truck just sitting in 2H.  I haven't tried locking the hubs and checking to see if it still turns tho.  Will try this tomorrow and let ya guys know.  Also I'm not real sure what the shifting procedure is for shifting this from gear to gear at the transfer case.  All the others trucks I own are later model trucks with just 2H, 4H and 4L.  With them i can shift from 2H to 4H while driving at a slow speed.  But to go from 4H to 4L, i had to go back to neutral to make the shift.  I'm not quite sure what the "rules" are on this for the np203.  Any help is greatly appreciated.
Title: Re: NP203 shift pattern
Post by: beastie_3 on November 05, 2009, 11:46:41 PM
Hello all,

Well I'm glad I'm not the only person out there not really understanding this whole np203 conversion.  I have recently (this week) purchased a 1979 C10 with the np203 behind a 350/350.  I am guessing that the conversion kit has been put in this transfer case because: One, it does have the manual locking hubs up front and Two, I can turn the front drive shaft with the truck just sitting in 2H.  I haven't tried locking the hubs and checking to see if it still turns tho.  Will try this tomorrow and let ya guys know.  Also I'm not real sure what the shifting procedure is for shifting this from gear to gear at the transfer case.  All the others trucks I own are later model trucks with just 2H, 4H and 4L.  With them i can shift from 2H to 4H while driving at a slow speed.  But to go from 4H to 4L, i had to go back to neutral to make the shift.  I'm not quite sure what the "rules" are on this for the np203.  Any help is greatly appreciated.

I have the same year truck with same drivetrain. First, you have a K10, not a C10. C10 is 2wd. K10 is 4wd. To answer your question, my original owners manual says you are allowed to shift from HI to HI LOC while moving as well as LOW to LOW LOC while moving. DO NOT shift from HI to N or to LOW or LOW LOC and vice versa while moving. You must be stationary with the transmission in neutral. I always shift the transfer case in neutral while stationary anyways. Also, when it comes time to replace your transfer case fluid, you must use 10w-30 or 10w-40, not to be confused with the 80w-90 that the NP205 uses.
Title: Re: NP203 shift pattern
Post by: Irish_Alley on November 06, 2009, 12:05:13 AM
about the weight of oil I cant help out but I thinks its different with the conversion kit installed and about going from low to hi while moving its not recommended before I put my 350 in mine the old engine was worn out and the 38's, going down the highway with a truck on my trailer I had to do just that top get up to speed, lol
Title: Re: NP203 shift pattern
Post by: beastie_3 on November 06, 2009, 12:24:18 AM
The only thing I can think of about using different weight oil is if the aftermarket T case kit recommends it. Otherwise, I would stick with the normal stuff. Same thing with shifting, I am just going off what the factory manual says. Even new vehicles wont shift like that. It puts too much stress on the drivetrain. It would be like going from 5th gear to 1st gear in a manual transmission on the freeway. (closest example I could think of)
Title: Re: NP203 shift pattern
Post by: tfdrooke24 on November 06, 2009, 12:41:34 AM
Thanks guys!! I had actually just overlooked that I put C10 instead of K10 while reading back on my original post.  I've been looking at so many different posts and googling so many different C/K10 pickups that i just got turned around. Its amazing some of the custom stuff guys have done on these old trucks.  I love reading through all these posts, i've learned so much already about this truck just by looking and reading.  What sites do you guys recommend for finding parts (body, drive train, suspension, interior) for these trucks.  Ive got a little body work to do and then get the interior back looking good.  I'm gonna try to post some pics of the ride tomorrow so stay tuned!!  Thanks again.
Title: Re: NP203 shift pattern
Post by: Donut on November 06, 2009, 07:37:06 AM
 :D Well, we know the "search" function works.

Parts-start with the banner at the top of the page (just click on it).  Don't rule out the local paper, Craigslist, junkyard, or a friend of a friend. (or your local GM dealer)
Don't rule out "driving around", there are still a ton of these trucks out there. A bunch parked out behind the barn, in the field (you get the idea)
Title: Re: NP203 shift pattern
Post by: force11b on November 07, 2009, 08:08:11 AM
My 1983s pattern is;

(front)
2H
4H
N
4L
(back)

What kind of transfer case would this be?
Title: Re: NP203 shift pattern
Post by: Irish_Alley on November 09, 2009, 02:27:12 AM
My 1983s pattern is;

(front)
2H
4H
N
4L
(back)

What kind of transfer case would this be?
that would be a 205
Title: Re: NP203 shift pattern
Post by: Irish_Alley on November 09, 2009, 02:39:23 AM
some pic to help you all out
203
(http://www.chuckschevytruckpages.com/images/anp203_.jpg)(http://www.chuckschevytruckpages.com/images/203shift.jpg)(http://www.chuckschevytruckpages.com/images/203shift1.jpg)

205
(http://www.chuckschevytruckpages.com/images/anp205.jpg)(http://www.chuckschevytruckpages.com/images/NP205knob.jpg)
sorry nothing for the 208
 you can find this at

http://www.chuckschevytruckpages.com/index4.html now i know hes not a sponsor but if theres any problems just delete the web page
Title: Re: NP203 shift pattern
Post by: tfdrooke24 on November 09, 2009, 04:33:53 PM
(http://i94.photobucket.com/albums/l116/Tfdrooke24/New%20Truck/000_0022.jpg)

The new rig!!

(http://i94.photobucket.com/albums/l116/Tfdrooke24/New%20Truck/000_0027.jpg)

With the NP203
Title: Re: NP203 shift pattern
Post by: Marc on November 09, 2009, 05:33:25 PM
A mid-late -70's W100/W200 Dodge has a shift knob which has the descriptions on it as it has a NP203 as well.
Title: Re: .
Post by: Russ130 on December 20, 2009, 10:56:14 AM
thanks aprice! i went to a 4wheel shop and they told me it's a np203 and that if you have locking hubs, its already been converted, which they do. He also told me that I have the wrong shift knob of the np205, and that mine is:

(front)
4L
2L
N
2H
4H
(back)

He said I should be in 2H for regular driving, but it really matters only when you lock up the hubs. Can anyone explain to me what each position is for? Sorry for the newbie questions, again, it's my first 4x4. Thanks!

btw, anyone know a place where i can get a new shift knob for the np203? <p></p><i></i>
This the shifting pattern I have after the conversion.  Its nice to have the 2l for pulling a heavy trailor or something like that where you don't need the 4 wheel drive.