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still truck

Discussion in 'Chevy Trucks' started by mudflinger78, Jan 24, 2006.

  1. mudflinger78

    mudflinger78 Junior Member
    Messages: 10

    I have a 78 scotts ck-10 which has a th-350w/np203 t/c. I talked to a couple of people about my problem; and I'm not sure of the conclusion. The problem is that I started my truck after I rebuilt the motor for the first time and went to drive it to find out that it won't go in to gear. The wierd thing is that I left the trany in the front shaft in; and linkage hooked up. It also has plenty of fluid. With the it in park I can turn the wheels either way. When I put it in 4wd the trany works it goes threw all the gears in the trans cause i'm putting the front wheels in gear. So to my knowledge the rear should be in gear or in park at all times when it's put there. so my guess is that the trany is damaged somewhere. If so how hard is it to seperate the trans from the transfer case? I have some one to do the work just don't know what to bring hin trans or transfer case. Thanks.
  2. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    I'm not sure I understand your description of the problem.

    Obviously it worked before you tore it down.

    You left the tranny, linkages, and driveshafts in place.

    There is no motion in any gear?

    You've confirmed that the wheels are all free and rolling, nothing is jammed etc.

    You didn't, by chance, forget to bolt the torque convertor to the flexplate, did you? Or not seat/bottom the tc properly in the tranny (assuming it was out at all) and force the tranny on, binding up the pump possibly?

    Forgive me if I've misunderstood something. :cool:
  3. mudflinger78

    mudflinger78 Junior Member
    Messages: 10

    yeah there is no motion in any gear except when it is in 4wd. The torque converter was bolted to the flywheel. The T/C was never off if that's what you were trying to say. I'm thinking that the trans is done because the rear wheels should turn no matter what. The only reason I can think that the trans works in 4wd cause the front wheels are running off the trans. When everything works and it is in 4wd is engaged both front and rear run off the trans. For instance if you take out the rear drive shaft and put your truck into 4wd your front wheels run off the trans; and your trans will still work as if the rear dive is in. So when driving down the road 2wd is always there when in gear even when in 4wd. With the rear wheels off the ground I can turn the wheels in park drive shaft moves too. The more and more I think about it I think the trans is done. Help if there's anymore ideas.
  4. bgingras

    bgingras Senior Member
    Messages: 282

    well, If I recal, the transfer case is after the transmission. if the only spinning you get is in 4wd then I would suspect that the transfercase is toast, allowing only power to go the the front when in 4wd and nothing at all in 2wd. if the transmission were gone, then you would not have any power to the transfer case to start with.
  5. sefh

    sefh Senior Member
    Messages: 439

    Does your driveshaft turn when you move the wheels?? Might be ring and pinion in stead of transmission or t/c.
  6. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    If you have motion in 4wd but not 2wd then the tranny is fine.

    When you jack up the rear of the truck and turn the wheels (in park), the wheels spin together (not opposite rotation) and the driveshaft turns, correct? Then the rear axle is functioning ok.

    So that leaves the transfer case.

    My advice would be, assuming it worked before you took it apart of course, is to check the linkages from the shifter on the transfer case that none of the little cotter pins broke from being shoved around during the install of the engine etc.

    Have you ever read any 4x4 Offroad magazines? Judging by your screen name I'd take a wild guess that you have. Remember how they talk about how they add a twin-stick shifter to control the front and rear axles independantly? They do it by scrapping the stock linkage that operates the two plungers on the transfer case in tandem, and replacing them with individual shifters and linkages.

    My guess is that possibly the rear axle's plunger has been shifted to neutrel somehow and is stuck there, possibly from a broken or disconnected linkage.

    Barring that, sounds like a bad transfer case... but that shouldn't happen sitting still, if you know what I mean.

    BTW, does your truck have a part-time conversion kit in that NP203? ie: manual locking hubs on the front and the mods inside the case
  7. mudflinger78

    mudflinger78 Junior Member
    Messages: 10

    I finally split the trans and T/C and found out that the trans is ok I think. The reason I say that is because when I put the torque converter in and turn it; the shaft at the end of the trans doesn't turn or should it? There are two splinned shafts at the torque converter end of the trans and one comes out of the other and the smaller one turns like it should I think and the bigger one doesn't. When I turn the smaller one in (park) the shaft at the other end doesn't move like it shouldn't right? When I put it into gear I turn the small shaft and the shaft at the other end of the trans turns; like it should right? When I put it back in to (park) and turn the small shaft it clicks and the shaft at the other end stops turning like it should right? Refering to the top about the torque converter. Now when you put it in to gear does the torque converter engage itself, something or lock something in when it's at idle to turn that small shaft to turn the other shaft at the other end of the trans? If so the torque converter is ok too. Now the side that the T/C slids on to the shaft of the trans there's enough area to grab (female end) and turn on the T/C; but when I turn it either way, on the other side of the T/C which is the tail section with a u-joint to hook up the drive shaft doesn't turn. Now that makes me believe that the T/C is shot. When I put the 4wd in gear and turn the drive shaft for the front wheels; the tail section for the drive shaft for the rear wheels also turn but not the (female side) that slides on to the shaft of the trans. So something in that area is shot right? HELP!! I think I'm getting closer in figuring this out with your help. thanks!!! P.S. I hope there is enough info to help you help me figure this out.
  8. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    I think you will be needing a shop to have a look at this, it is too hard to diagnose this thru descriptions.

    A NP203 transfer case is originally a full-time 4x4 transfer case. If you have 2wd as an option and manual locking front hubs (confirm here) then someone has added a part time conversion kit.

    Part time kits have their own list of problems, so perhaps something has failed. One of the largest complaints resulting from the installation of one is a lubrication issue, since the tcase relies on the chain's motion to lubricate certain parts. It is recommended that 4wd be engaged at least once a week (more often is better) to maintain proper lubrication. If this was not done, there could very well be damage in there.

    You still haven't confirmed that this was in working condition before the engine swap.

    Also are you certain it is a 203 and not a 205?

    I'd say take it to a shop and show them, get their opinion based on what they see and report back to us.
  9. mudflinger78

    mudflinger78 Junior Member
    Messages: 10

    I'm pretty sure it's an np203 to my understanding that the np203 has 2 lows and 2 highs and a neutral. How do I find out for sure? does it say on the T\C some where? I don't have manual locking hubs. Can I see if there's a part time 2wd. yes the T\C did work before prior to pulling the motor.
  10. Joe D

    Joe D Senior Member
    Messages: 605

    The 203 uses a center diff which gives you the full time feature with high and low range, it also alows you to lock in high or low range. I would bet the diff is gone. I like the the 203 for the full time 4 wheel on a plow truck.
    Double check shift linkage and fluid level. If it's just swap it out for another one, they are pretty common in the bone yards
  11. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Most don't have tags on them anymore, as they rot from salt.

    The easiest way I know of to tell a 203 from a 205 is that while they look nearly identical and are both cast iron, the 205 has a small round cover on the rear (approx 2" dia?) with three bolts holding it on. The 203 doesn't have this.

    Joe is probably correct on the center diff being gone if its a 203. It would only drive in one of the two LOCK positions. The lack of manual locking hubs on the front says it is "probably" an original full timer without the part time kit. You wouldn't have a 2wd position.

    Look on ebay. No one really wants 203's, so they go dirt cheap. I've seen them as cheap as $20.

    Funny that it just died like that... but stranger things have happened.
  12. mudflinger78

    mudflinger78 Junior Member
    Messages: 10

    hey derek you mentioned that my 4wd would only lock in one of the two positions. The problem is that it locks into both; which isn't a bad thing. I thought if I put the 4wd in neutral with the shifter on the floor it would go into 2wd. That's how it worked before it quit working I thought. where should the shifter for the 4wd be postioned when in regular use? like it was said earlier something in the linkage(4wd) might be off or bad. I might have to go with double shifter. I would assume that it would go in high not high lock right or shold it go in to low not low lock
  13. wfd44

    wfd44 Senior Member
    from Maine
    Messages: 369

    First you are confusing the h*** out of me with all the trans and T/C. I can't keep it straight whether you are talking about "trans"mission, "trans"fer case, and whether T/C means "T/C"ase or "T/C"onverter.

    You can not accurately diagnose an automatic transmission without an engine actively driving it (in the shadetree world). This is because it takes hydraulic pressure to actuate servos inside it and shift it. To further explain it would require a full day of Automatic Transmission theory. Suffice it to say that you are getting drive in certain transfer case positions so we assume the transmission is OK. They don't usually die overnight and baring a catestrophic failure (abrupt disassembly without the aid of hand tools) they generally show signs that they are about to s*** the bed.

    Your transfer case - if it has the following positions on the shifter: High Lock, High, Neutral, Low and Low Lock and the truck has blind caps where the manual locking hubs usually are then you have an NP 203 transfer case (originally full time 4wd - current status unknown). I would be pretty sure that your problem lies here. As stated before probably either the transfer case differential or shift linkage issue. If you need to fix it or replace it this is also the ideal time to convert it to part time 4wd.

    Neutral on the transfer case shifter is for flat towing and/or PTO operations. It does not and should not deliver any power to the wheels. If it does or did then that is further condemnation of the transfer case.
    Last edited: Jan 30, 2006
  14. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    In stock form, an NP203 has NO 2wd position. It is a full-time 4x4 transfercase.

    For normal driving, it would be driven in the regular 4HI position. You would also have 4HI Lock, 4LO, and 4LO Lock... and a neutrel.

    Neutrel is typically for running PTO's. The Lock positions disable the differential in the t/c that Joe was talking about above... for optimal 4x4 traction in slippery conditions... the other two are for on-road useage.

    Tell us what the front hubs look like:

    You say they are not manual hubs... there are two other kinds. One is just a solid cap (fairly large, most were originally chrome) with nothing on it at all. The other is the smaller chrome cap with the 4x4 logo on it and tiny allen bolts surrounding the perimeter.

    You need to identify what you have. Anything we are talking about here is all guesswork until you can tell us for certain that it is a 203, and the hubs on the front axle.

    You should also be able to operate this thing on a bench, turning the yoke and moving it thru the gear positions on the two plungers. They need to be in the right combination to operate correctly.

    I'm sure there are people better qualified to talk about the 203 than me, as most of my experience is with 205's.
  15. tuna

    tuna Senior Member
    Messages: 488

    If it is original a 78 K10 with an auto trans has a 203 and the front hub will have the smooth cap.The auto hubs that say 4x4 are on the 208 that came along in 1981.
  16. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    That is a big IF it is original. Alot of things get changed on a truck in 28 years.

    For example, I recently picked up an '89 Suburban for parts. It has a 12 bolt rear, 10 bolt front with one manual locking hub on one side and a full-time hub on the other!

    Note that neither the rear axle nor either of the front hubs are original to a loaded Sub.