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1978 3/4 Ton with 4x4

Discussion in 'Chevy Trucks' started by bcofdayton, Dec 1, 2009.

  1. bcofdayton

    bcofdayton Member
    Messages: 55

    Looking at a '78, the owner has no idea what is 4W Low or 4W High. There are 4 positions on the 4wd. All the way forward a 4wd light comes on, first position ?, 2nd position back ?, third position 4wd light comes on. There is no layout on the handle or any sticker anywhere. Any ideas?
  2. ahoron

    ahoron Senior Member
    from here
    Messages: 422

    forward should be low then neutral then 2wd and back 4 high
  3. bcofdayton

    bcofdayton Member
    Messages: 55

    Thanks, HUGE help!
  4. purplehavoc

    purplehavoc Member
    Messages: 97

    Is it auto or stick?
    If it is auto of that era,they had the NP203 behind them which is a full time
    transfer case. All the way forward was Low loc,low,netural,high,high loc.
    The part time NP205 was found behind the manual trans.
    The 203 was a decent t-case,just watch for chain slop.
  5. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    also 74ish there was a 4speed with the 203 full time tcase. but ultra rear item. off road guys love them for building rock crawlers.

    but if your shifter shows a loc postion then its a 203 fulltime tcase. but might be possible to have a parttime kit in it by now tho. if it has selctable lock out hubs on the front axle it should have a part time kit then. as a full time tcase will not work right with hubs unlocked.

    if the shifter only shows 2wd/4wd/n/4low then 203 tcase. great super strong unit.

    and 78 and 3/4 ton prob auto and th400 tranny and 203 full time tcase.
  6. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    That would be a 205, not 203. Isn't the shift pattern the same for the 208 also?
  7. bcofdayton

    bcofdayton Member
    Messages: 55

    I drove it, the problem is that there isn't any label on the 4wd shifter or nearby. How would I find out what it has? What is the difference between low and low loc? It does have manual locks on the wheels. I've always been a Ford man, this is all new. Thanks for all of the help
  8. bcofdayton

    bcofdayton Member
    Messages: 55

    It is a 3/4 ton automatic, the automatic seems to be 3 speed
    Last edited: Dec 1, 2009
  9. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    If you go under the truck, on the back of the tcase by the output for the rear drive shaft, there should be a plate with what kind of tcase it is. Could be rotted off by now though.
  10. bcofdayton

    bcofdayton Member
    Messages: 55

    I do have an auto, so will it possibly be in low or high without locking the hubs?
  11. purplehavoc

    purplehavoc Member
    Messages: 97

    Since it is auto chances are it is a 203 that was converted to part time.
    As mentioned probably a turbo 400 trans.(strong)
    If there is still a tag on the t-case see what number it has,otherwise try moving the t-case shifter through each range and moving the truck.

    The np205 will only have low 203 lo loc
    neu low
    2hi neu
    4hi hi
    hi loc.
    Been along time since i shifted a fulltime case,so i think that is right.
    Low range should be all the way forward for low range.
  12. welded wrenches

    welded wrenches Senior Member
    Messages: 177

    shift what

    this is a easy question .is the 4x4 shifter handle rectangular it is a 203 full time chain drive casriron case n may have after market part time kit in if the truck has lockout hubs..thethe other t-case gear drive is a np205 with a 1.96 low range (the best one.)cast iron case has a round shifter handle round like a tire iron.shift pattern is forward 4L -N -2H-4H if the t case is aluminum its a 208 chrome round handle forward to rearward 2high 4 high nuetral 4low ...with a 2.61 low range ratio tons of truck info at chuckschevypages.com or coloradok5.com
  13. bcofdayton

    bcofdayton Member
    Messages: 55

    Chuck's had everything I needed including pictures. For anyone interested this is where I found what I needed to show the shift pattern: http://www.chuckschevytruckpages.com/drivetrains.html

    I still don't know when I should use L loc or L vs. H loc or H? Do I not need to lock the hubs when I use one or the other? I realize the difference between 4H and 4L just don't get the loc part
  14. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    darn it you got my type o goof up.

    yes i meant 205 tcase. :dizzy:
  15. tuna

    tuna Senior Member
    Messages: 488

    A 203 if it has not been converted to part time 4wd is a full time 4wd that has a differential in the transfer case.This alows the front and rear to spin at different speeds around corners on dry pavement .It works the same way as an open diff in your rear axle ,if you loose traction at the rear it will send all the power to the rear .You have a Hi and a low in this open mode.When you shift in to hi loc or low loc it locks the differential in the case sending equal power to both front and rear this would be the prefferred mode for off road or plowing.They came without locking hubs because the system would not work in the non lock postions because the differential would send all the power to the unlock hubs .If yours has locking hubs somebody probably put in a part time conversion kit ,the 203`s in stock form tended to be gas guzzlers so most were converted it is very rare to find one today that has not been converted.I`m not sure of the shift pattern of a converted 203 but I`m sure someone here does.
  16. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Shift pattern on a converted 203 is...

    • 4 Lo
    • 2 Lo
    • N
    • 2 HI
    • 4 HI

    2 Lo can be very handy. :nod:
  17. bcofdayton

    bcofdayton Member
    Messages: 55

    Now I have all of the pieces to the puzzle! The truck runs great, I got it with a plow, plow extensions, & a tool box in the bed for $2K, ready to plow! He's not the prettiest but like I said everything works and runs out great :)
  18. JohnMeyer

    JohnMeyer Member
    Messages: 31

    The NP 203 was the Full Time four wheel drive. There was no 2 wheel drive position on it. The positions front to back were Low Lock-Low-Neutral-High-High Lock. I had a 1977 Chev K10 with the full time 4wd, and drove it for 22 years. I had to work on the engine and transmission but not the 4wd! They were excellent plow trucks. Occasionally you can find a survivor here in upstate NY. The rust killed most of them.