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Thread: Locking Hubs on '79 K-5

  1. #1
    Shadetree Mechanic
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    Locking Hubs on '79 K-5

    Here goes. I bought my "new" 79 the other day. It has warn locking hubs. Apparently the OEM was "Quadratrax"? I'm sure yall know better than I do. But, when I put the hubs in "free" with the floor shifter in "HI" I have a problem. When I try to put the transmission into any gear, it feels like the transmission is "free spinning" and makes a grinding noise. The only way to make the truck "go" is one of two ways: 1. Lock the hubs and put in "HI" and the truck goes but I cannot get the rear wheels to spin even in gravel. 0r 2. Put the hubs in "free", put in "HI LOC" and the truck also goes. In the second configuration, the rear wheels will spin in gravel very good.

    The problem is the "4 wheel drive" light is on when I have it in "HI LOC". Is this a problem? Is either configuration a problem?
    I can get a set of the original hubs that seem to be brand new. Should I do this and go back original?

    My floor shifter is labeled like this (closest to dash going to rear) LO LOC, LO, N, HI, HI LOC.

    Any help would be appreciated.

  2. #2
    Enjoying Life Chief Hunglikmule 70-K5's Avatar
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    Your t-case is a NP203, it is paired with automatic locking hubs. You can replace the hubs with manual like the ones you have but you also have to change things around in the t-case.

    Sounds like you don't have the part time kit in your t-case.

  3. #3
    (Brent) Senior member NightKrwlr's Avatar
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    Quote Originally Posted by 70-K5 View Post
    Your t-case is a NP203, it is paired with drive slugs. You can replace the hubs with manual like the ones you have but you also have to change things around in the t-case.

    Sounds like you don't have the part time kit in your t-case.
    203s came with drive slugs. they dont have a choice to be locked or unlocked. the hub and axle are always locked together.
    Last edited by NightKrwlr; 01-26-2011 at 08:41 PM.
    When the clutch drops... the bullsh*t stops

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  4. #4
    Shadetree Mechanic
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    Thanks for the help so far, but......I'm pretty new to the "non-push button 4 wheel drive" So.......without fear of sounding stupid, is it ok to drive in either configuration? Especially #2, since it doesnt seem that the front drive line is putting power to either wheel? Thanks in advance.

  5. #5
    $6Million man in progress Senior member Timberdoodles's Avatar
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    On dry pavement, you ONLY want to drive in 2Hi, with power to the back wheels. You can damage your T-case and hubs by driving in 4x4 on dry asphalt/cement, where they don't have a chance to slip some.
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  6. #6
    Enjoying Life Chief Hunglikmule 70-K5's Avatar
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    2HI is equal to HI on your setup.

    Hopefully somebody will chime in and explain the full time 4wd case because I don't really understand it either.

  7. #7
    Senior member Doppler's Avatar
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    Stock NP203 doesn't have 2HI does it?

  8. #8
    (Brent) Senior member NightKrwlr's Avatar
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    quote from here: http://www.4wheeloffroad.com/howto/47538/index.html
    The full-time four-wheel-drive NP203 transfer case is one of the most standard items found in ’70s fullsize 4x4s. Big, heavy, and relatively strong despite its chaindrive, this box can be converted to part-time with a simple gear or shaft swap inside the case. But few people understand how the insides tick on this case, so we thought we’d clue you in to some of the innards and theory without a complete rebuild or overhaul.

    The full-time aspect of the 203 is all in the rear section of the unit. The case has an internal differential that selectively splits the power to the front and rear axles when the shifter is not in one of the locked positions. When shifted into Hi-Loc or Lo-Loc, the differential locks to provide equal power to both driveshafts. If you removed either driveshaft and tried to drive the truck with the case in the nonlocked position, the internal diff would send all the power to the yoke with the missing shaft. It’s just like an open rear axle differential, where all the power goes to the tire with the least traction. However, if the case was shifted into a locked position, power would be equally distributed to the front and rear, so you’d be able to drive the rig as long as one driveshaft was still in place.

    Many of you with 203s are running around without a front driveshaft and with the shifter in Hi-Loc since that’s the free method of overriding the full-time 4x4 feature. But after a while you’ll probably notice a clunk emanating from the case. Whether your rig is a Dodge, a Chevy, or a Ford, the NP203 will develop internal wear when subjected to this type of use. Minimal driving isn’t a problem, but continual driving in the Hi-Loc position without the front shaft installed causes the internal coupler on the differential to develop a lot of slop, eventually causing a banging noise and then destruction.

    The differential carrier is also an item that can shred with this type of abuse. Many 203 cases use a pressed-steel cage for the differential gears instead of the two-piece heavy-duty style, and Jason Bunch at Tri-County Gear says the pressed-steel unit wears out quickly if you do a quasi conversion this way. The best bet is to install a conversion kit in the 203 case and add locking front hubs to eliminate wear and drag on the front axle internal components. Even the ’74-’79 Dodge trucks and Ramchargers with the live-axle front end can be converted to use hubs with a MileMarker kit.
    When the clutch drops... the bullsh*t stops

    Current:
    2005 EC/LB 2500HD Duramax- 4" fabtech lift, 5" flo pro, EFI live, EGR block, PCV reroute, LBZ turbo mouthpiece, future mods-suncoast stage 5 trans

    Past:
    1988 K5 the Night Krawler
    1990 K5
    1976 Jimmy, 7" susp 3" body, 40" ground hawgs
    1995 2500, SFA HPD44, 14bff, 350/nv4500/np241

  9. #9
    Shadetree Mechanic
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    thanks to all! I think I understand the configuration better. Im gonna drive it until something breaks and that will give me an excuse to re-build it. LOL Thanks again! Going to try and download some pics

  10. #10
    Knows their $hit burntclutch's Avatar
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    Quote Originally Posted by BLAZER CRAZY View Post
    thanks to all! I think I understand the configuration better. Im gonna drive it until something breaks and that will give me an excuse to re-build it. LOL Thanks again! Going to try and download some pics
    Drive it til it breaks! Spoken like a tru chevyk5blazer.com brother,,,,welcome to the family,,,,Brother!!!

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