73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Transfer Cases and Front Drivelines => Topic started by: Chadwick717 on April 06, 2014, 07:15:24 am
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Hey guys. Newbie here with an extreme newbie question. I just picked up a 79 c-10. Through this
forum I've been able to do some searches and I figured out that I have a np203 transfer case and a part time kit. (The truck moves in hi without the front hubs locked.) I am however, having trouble shifting the transfer case, and making sure I am in hi only. What is the proper process for shifting between lo lock, lo , hi , hi lock? And how do I make sure I am in hi only? Thanks so much for the help I have learned so much already here.
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It's easy to figure out from the shifter, unless your shifter is loose, so I am assuming your shifter is loose. Also, there is a switch on the shifter box that indicates on the dash, so I am also assuming your dash indicator is non-functional.
First thing. There is a chrome piece of the shifter that sticks up out of the boot into the cab. There is an unchromed piece that actually goes into the shifter box on the front of the transfer case. These are bolted together under the boot. If they get loose, the shifter will feel wobbly, and move around without shifting the shifter box.
Remove the boot -- four screws, trim ring comes off; four more screws, boot comes off. Identify the two bolts in the shaft. Tighten 'em up. Replace boot and trim ring. The shifter should now be solid in whatever position you shift the case into, and you can tell what mode it is in by the distance the knob is from the seat.
Second thing. There is an indicator on the dash. Probably the left one in the speedometer. Look up in behind there with an inspection mirror and a flashlight. Is there a bulb holder there with white and brown-with-white-stripe wires coming from it? That's the "4WD LOCK" indicator lamp. Now, when you have the boot off in the above step, notice the white and black wires that come out from under the carpet and go down through the hole. Those go to a 4WD indicator switch on the very front of the shifter box. Look down through the hole and you should be able to see the 4WD indicator switch.
To debug all this: First, pull the lamp holder in the dash. It twists one-eighth turn in the "unscrew" direction and pulls out. Is there a bulb in it? Is the bulb good? Get underneath the truck and pull the connector off the switch. Short the switch connector with a piece of wire. Does the bulb light? Is the switch adjusted properly? To adjust the switch, push it deeper into its mounting hole, then shift the shifter into LOC and back out. The switch is self-adjusting in the hole, in that it will push out to the correct position.
Finally, the switch may be dead. NOS GM part will cost you a hundred bucks. However, there is a reproduction made that works. It's what I am using. It is also used by GM as the throttle arm position indicator on a 1969 Camaro cowl induction setup. Here it is:
http://www.heartbeatcitycamaro.com/store/product/13747/Camaro-Cowl-induction-throttle-switch-1969/
You probably should replace the mounting clip as well.
http://www.heartbeatcitycamaro.com/store/product/13748/Camaro-Cowl-induction-throttle-clip-1969/
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Great info! Thank you so much. I'm gonna start looking to the indicator lamp when I get home. I guess my question is also a little more basic than that. I have an automatic so should the truck be in park or neutral when shifting the transfer case? When I'm in hi the transfer case shifter knob should be straight up correct? And hi loc angled back towards the seat? Mainly I'm concerned about driving on the roads in hi loc accidentally.
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There is a great write up on chuckschevypages.com on how to properly adjust an np203. I swaped my 203 for a 205 my 203 shifter levers were all messed up the shifter kept shifting into neutral good luck with the 203 its not real easy to adjust when in the truck
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I guess what I'm asking is how to tell if I am in hi or hi loc with the part time kit. When I think I'm in hi, the front shaft still spins when I watch the truck drive away, but I can get down and spin it with my hands.
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You can shift from HI to HI LOC and back any time when the hubs are in LOCK, such as in the winter if you lock the hubs before you leave home, as I do. I normally lock them on first snow and keep them locked more or less all winter, for sure any time there is a chance of bad conditions. I put them in FREE once the weather turns.
When the hubs are in FREE, you can shoot from HI LOC to HI any time, but the vehicle must be stopped or moving very slow (1-2 mph) to shift from HI to HI LOC. This is because the front hardware is either not spinning at all or only spinning slowly due to drag in the hubs and transfer case. So you can't slide the splined collar onto the splined part of the shaft when they aren't close to the same speed.
When the hubs are FREE and the transfer case is HI, there is no oiling of the rear output shaft bearing of the NP203. It was designed to be full-time, so there is no oil pump per se. The chain for the front drive flings oil against the inside of the case, which runs down into oil ways and back to an oil reservoir for the rear output shaft bearing. You can drive that reservoir dry, and then burn up the rear output shaft bearing of the transfer case. MY solution is to put the transfer case into HI LOC for the first couple miles of my first drive of the day, to fill that reservoir, then shift out of HI LOC to HI, which I can do while moving. There is no need to do this when the hubs are locked, because the hubs are driving the differential, driveshaft and the chain in the transfer case, oiling the rear output shaft bearing reservoir.
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I guess what I'm asking is how to tell if I am in hi or hi loc with the part time kit. When I think I'm in hi, the front shaft still spins when I watch the truck drive away, but I can get down and spin it with my hands.
Fix the indicator lamp.
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Rich thanks for all the help. I'll get on that indicator lamp.
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this is all very useful information!
I just got a '79 a few weeks ago and was doing some reading trying to find out more about it and it turns out mine has the part time kit 203 aswell (low loc-low-n-hi-hi loc shifter) and it has lockout hubs.
i was not aware that i could drive around with the hubs locked and switch from high to high lock at any time while moving
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this is all very useful information!
I just got a '79 a few weeks ago and was doing some reading trying to find out more about it and it turns out mine has the part time kit 203 aswell (low loc-low-n-hi-hi loc shifter) and it has lockout hubs.
i was not aware that i could drive around with the hubs locked and switch from high to high lock at any time while moving
Yeah, just as long as you are not spinning the rears. When you go from HI to HI LOC, both axles have to be going the same speed. I kick it in and out of LOC on the fly a lot in the winter when the roads are clear but the parking lots and side streets still aren't.
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awesome good to know!
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Quick update. I did get under the truck yesterday while changing the oil and I saw that the connector to the switch was disconnected, so I reconnected it. (http://img.tapatalk.com/d/14/04/08/2umabuva.jpg)
Still no light on the dash, and I ran out of time, so I need to check the bulb, but I ran out of time.
I did find the pins holding both rods to the shift knob were gone, both rods were still in the holes on the levers, but I replaced the pins. Still can't tell from feel if I am going In between hi or hi loc. I can shift into neutral and down into lo and lo loc, then back into neutral, and back into one of the hi-s. Basically it feels like there is only one option on the hi side of neutral. Should the be a noticeable clunk or something going from hi to hi-loc? I guess I need to get under there and adjust the linkages per chucks chevy pages.
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No clunk if stopped. If you are going 1-2 miles per hour, there should be a clunk when it engages.
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If you have a stock NP203 I don't think they ever included a dash indicator lamp.
Also, if someone has added locking hubs you also have non-factory setup that won't work the same as original. Locking hubs were never an option with the NP203 because it was full-time 4WD. There is a differential in the transfer case that allows it to stay in AWD all the time. The shifter changes from high to low range, and locks the transfer case into true 4WD.
A stock NP 203 has a shift pattern of:
LowLock (2:1 gear reduction, Tcase differential locked to 4WD),
Low (AWD, 2:1 gear reduction),
Neutral,
High, (AWD)
HighLock (Tcase differential locked to 4WD)
After a part time conversion kit installation (e.g., Milemarker 501 kit) the shift pattern becomes:
4x4 Low
2x4 low
Neutral
2x4 High (Normal Street use)
4x4 High
Bruce
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If you have a stock NP203 I don't think they ever included a dash indicator lamp.
Beg to differ. My 78 K10 had one as built, which was extra wiring outside the normal harness, the switch on the shifter, a lamp socket on a pigtail, and the plastic lens with 4WD LOCK lettering on the LHS lamp behind the speedometer. The switch on the NP203 shifter mounts in a bracket that is part of the shifter and has no other purpose. The 1978 parts book calls out the switch.
On mine, the lamp was burned out, and the switch was broken. I replaced both and now have the indicator lamp functional with no changes required.
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so i talked to my buddy that i bought the truck from and turns out he was the one that installed the lockout hubs and before that it was full time awd so it does not have the part time kit as i had thought.
also i had the gauge cluster apart and noticed there is the 4wd lock lamp there. but i know it does not work. its a 79
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OK, so that is why you can't figure out the shifting. If you have it in HI, the open differential in the transfer case will try to run power to front and back, but with the hubs in FREE, the truck is going nowhere. All the power will go to spinning the front axle and you will think you are in neutral. HI LOC will lock the differential so the rear wheels will get power.
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that sounds pretty much right cause i went all the way up to low and tried to count down to HI and when i got there it wouldnt go anywhere(after i unlocked the hubs) so i had to drop it down one more to get it to move i assumed that was actually HI not HI LOC due to slop in the shifter
sooo i have to keep it in HI LOC all the time in order to drive with the hubs in FREE? and to actually engage 4x4 I gotta get out and lockt he hubs
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that sounds pretty much right cause i went all the way up to low and tried to count down to HI and when i got there it wouldnt go anywhere(after i unlocked the hubs) so i had to drop it down one more to get it to move i assumed that was actually HI not HI LOC due to slop in the shifter
sooo i have to keep it in HI LOC all the time in order to drive with the hubs in FREE? and to actually engage 4x4 I gotta get out and lockt he hubs
Exactly correct. And once the hubs are locked, you have the option of open differential (HI) or locked differential (HI LOC). Note that you can drive with the hubs locked on dry pavement as long as the transfer case is in HI. So this is a good choice for winter, when you have a mix of conditions. Lock the hubs, then drive in HI on dry/clear pavement, and go to HI LOC when you need it (but only on loose surfaces!).
And that isn't slop in the shifter itself. The bolts in the shifter lever (under the boot) are loose. 15 minute job to tighten those up.
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understood!
what i meant by slop in the shifter was that i thought the shifter was sloppy because i couldnt get it to move in hi with the hubs unlocked so i was assuming it was sloppy between N and HI but really the hubs were unlockd and it wouldnt move in hi as you said
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So I finally got the chance to mess with the truck again today. My oil pressure gauge scared me to death and dropped to zero. I put on a mechanical tester and it was showing 35 psi at idle, so I replaced the sending unit (thanks to what I learned on this forum) and it now works fine.
After I got that taken care of I climbed under the truck to adjust the rods linking the shifter to the np203. When I placed the shifter in neutral it looked pretty good already. This is what I got.
(http://img.tapatalk.com/d/14/04/15/pu9y8uny.jpg)
I did have a drill bit in the gauge pin hole, and it looks like it is pretty well adjusted? I still did not get the light fixed, but I am unable to discern 2 different positions after neutral. It feels like only one.
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Here is a video of me trying to shift the transfer case. The video is not great, so I'll try to explain what I am doing. I shift the automatic transmission into neutral, then I'm able to place the transfer case into what I think is neutral. I then place the truck into reverse, and give it some gas. It doesn't go anywhere, confirming that I am in neutral on the transfer case. I then put the transmission back into neutral and try to shift the transfer case back into hi, and you can hear the grinding, it won't go. I then place the transmission into park and you can hear the weird ratcheting sounds coming from the transfer case. I am then able to place the transfer case into hi. I think.
http://youtu.be/9hu80vhJ--c
Is it supposed to sound like that weird ratcheting noise? Why can't I shift out of neutral into hi when the transmission is in neutral? Thanks for all the help! I am trying to figure out this transfer case.
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This is completely normal operation. There is drag through the transmission in neutral that will spin the innards of the transfer case. You have to have the transmission in PARK to shift out of NEUTRAL on the transfer case in either direction. Putting it in PARK keeps the output shaft of the transmission from turning so that the transfer case internals are stopped: then you can shift from NEUTRAL into HI or LO. The "weird ratcheting sounds" you here when you put it in PARK with the engine running are not from the transfer case, they are from the transmission trying to catch the parking pawl. If you do find yourself in NEUTRAL of the transfer case without the tranny in PARK, you should shut the engine down to bring all the innards to a stop so you can shift the transfer case out of neutral without breaking anything.
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Ok. That makes sense. Thanks for all the help Rich. I'll get this figured out eventually.
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Will the front driveshaft keep spinning with the part time kit and the transfer case in hi?
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I just ended up installing a 205 the 203 was fine my shifter was all fubar i had the drive shafts and hubs from a previous truck i like the 205 much better than the 203 i had a 1x6 jammed between the shifter to hold it in hi for about a month it didn't want to stay locked in at all
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Will the front driveshaft keep spinning with the part time kit and the transfer case in hi?
Not if the hubs are in FREE. If the hubs are in LOCK, it will spin, because it will be driven by the wheels. But mine does not spin at all in HI with the hubs in FREE.
There's an issue if the hubs are in FREE because of the way the NP203 oils the rear output bearing, so the first time I drive it every day (if the hubs are FREE), I put it in HI LOC for two miles to fill the oil reservoir for the rear output shaft bearing, then just pop it into HI on the fly.
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Was just messing around in the truck trying to find hi and I knocked it into neutral. I went to shut the truck down, but I can't unless the shifter is in park. So basically don't get into neutral unless the truck is turned off?
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Or in park
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Ok I got my dash 4 lock light to work. I pushed it into lo loc and it came on. Still have not been able to get it into hi loc. here is a video of me driving in what I think is hi. You can see the front driveshaft spins a bit at first but then stops spinning even when I give it a bit of gas. I then try and shift into hi loc, but am unable to. Could there be binding in my transfer case or shifter? Also when I got it down into lo loc and drove with the hubs unlocked, the front driveshaft was not spinning. I thought in lo loc it would spin all the time, even with the hubs unlocked.
http://youtu.be/oVzp1xie3R4
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In LO LOC and HI LOC, the front driveshaft should spin all the time, even with the hubs in FREE.
Yes, don't go into neutral unless the engine is off or you are in PARK.
I would start by liberally dousing the shifter box with something like Silikroil or PBBlaster, to make sure nothing is stuck in the shifter itself. You can just pour it all over it from the top through the shifter hole in the floor, and see if it frees up. Mine is easy to shift back and forth through all five positions. If the 4 LOCK light doesn't come on in HI LOC, then the LOCK lever to the NP203 is not moving far enough to engage HI LOC.
You could have a busted chain packed up in the NP203 or something drastic like that, but it may just be a balky shifter box.
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Ok. That's the next step. My only concern now is the front shaft not spinning when I was in lo loc. truck drives around nice with no noises from the transfer case during normal driving, besides a clicking noise outside of the passengers window.
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Ok quick update. Thanks for the patience as I figured this out. It was tough not knowing exactly what was going on. I sprayed some pb blaster down the shifter box and let it sit. Came back out and it was like I had a new shifter box. I now have five definable positions a long with a working light on the dash. I drove it around in hi loc with the hubs free and the front driveshaft spins right along with the back one like it's supposed to. I'm pumped!! Thanks for all the help Rich!!
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I love it when the magic works.
Glad you got it sorted. BTDT on all of the above, but it took me longer to figure it out! Those shifter boxes can give trouble because they are exposed to all kinds of road dirt and dust, so cleaning it out good once in a while is necessary. You probably want to run a little engine oil down into it now that you have it freed up and operating properly.
Enjoy. And don't forget if you have the hubs in FREE that you need to oil that rear output shaft bearing. Run it in HI LOC for a couple miles the first time you drive it every day, then shift into HI, which you can do on the fly.
[edit] Actually, if you don't have the part-time kit in it, you don't need to run it in HI LOC to oil the rear output shaft bearings. You will either be hubs in LOCK or transfer case in HI LOC, or you won't move. Either will oil that bearing.