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T-Case Questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by acablik, Jul 31, 2002.

  1. acablik

    acablik Registered Member

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    Hello, I just bought a 75 K5 and I think the t-case is bad. I dont know which one (203, 205, 208) it has in it but it has manual locing hubs and a th 350 transmission, 12 bolt rear dana 44 front, 35" tires, built 350 engine. I dont know the t-case pattern b/c I dont know which one it is, but I have tried all diffrent positions with no luck.
    I suspect its a 205 b/c it works fine in two wheel drive.
    My questions are:
    1. which t-case is it?
    2. If it needs replacing, which one should I use 203, 205, 208???
    3. What other parts will I need to swap t-cases with another model, are all NP's interchangable?
    4. Is it easy to do, how long will it take assuming I am a decent mechanic and have nice tools?
    5. Are special tools needed?

    Sorry for so many questions but I am ready to get this thing on the trails!! Thanks in advance for your help!
     
  2. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    sounds like a 205 b/c 203's are full time 4 wheel drive and I don't think 75's came w/ 208's
     
  3. CooknwithGas

    CooknwithGas 1/2 ton status

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    I have a 1975 blazer and it has an NP203. I'm sure yours is the same unless it has been replaced with something else (doubtful). You can find lots of information in a shop manual (ebay has them for cheap), or a chilton's manual. Mine has a little play in it and I think that is not good, but it works just fine. I hope this is helpful.
     
  4. trailblazer87

    trailblazer87 1/2 ton status

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    What makes you think that the t-case is bad, both the 203 and 205 are pretty hard to break. It could be a 203 with a 2wd conversion kit. The only way to tell would be to check the tag on the back of the case, also if it chain driven it is a 203, if not it is a 205. Another test would be to put it in 2wd and slowly move the truck and have someone see of the front driveline spins. Someone might have put manual hubs on it to help with the on-road manners.
     
  5. BLUESMAN

    BLUESMAN 1/2 ton status

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    Well I'm guessing the 203 case,but we should could use some for info!If it is the 203 then it might be the chain has bit the big one.Now the Q is to repair what you have or replace it.Cheaper to replace the chain if that is the problem.Both the 203/205 cases are damn strong.Adapting an NP208/241 can be easily done,but you will need driveshafts(maybe get them from the donor truck).You are locking in the frt. hubs,right?It only drives in 2WD?,no lo range or hi?Give us some more info.Mike
     
  6. acablik

    acablik Registered Member

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    I have the t-case lever all the way down right now and it drives in 2wd. I lock the hubs out when I try to put it in 4wd. If I put my transmission in neutral, it allows me to push the lever forward. But it still does not engage into 4wd. Could the linkage be messed up? The transmission shop says its the t-case but I dont think they know their Azz from a hole in the wall!!! What else can I try? Does this info help ID it as a 205 or 203??
     
  7. MR.4x4

    MR.4x4 Registered Member

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    Hi, i have a Blazer 75 with a np-203.

    If your trans is Automatic you should have the 203
    If your trans is standar you should have the 205

    208 wasnt in the 75

    If you hear some loud Clicks, your chain may be loosen and you have to change it (100 dll new) Aprox.

    The np-203 its full-time (you could have the part time kit)
    The np-205 is part time (Factory)

    I hope this is helpfull!!!
     
  8. m j

    m j 1/2 ton status

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    ID a 205
    from the rear there is a small round cover held in place with 3 bolts
    chucks pages are real helpful here

    a 205 is the best TC easily available for these trucks.
     
  9. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Check for these things to identify which t-case you have:

    NP 203
    The shifter will have a metal plate/square ring at the base to hold the rubber boot in place.
    On the left side of the metal plate you should see some letters/numbers which will identify which range you are in. The letters/numbers go in order as:
    4 Lo
    2 Lo
    N
    2 Hi
    4 Hi
    These markings on the plate will tell you that the t-case is the NP203.

    NP 205
    Check the knob to see the letters/numbers stamped on it. They should read:
    4 Lo
    N
    2 Hi
    4 Hi
    There is no markings like the NP203 plate on the floor. NP205's use a regular metal plate/ring around the boot on the floor.

    NP 208
    These were not started til '81, but you never know as someone could have swapped this into the truck you have. To identify this t-case:
    Check the shifter and see if there is a black plastic box at the floor/base part of it. If the shifter is sticking out of a black box, and angled towards the firewall, it may be the NP208, but I'm doubting this since these were not available until 1981.
     
  10. Muddytazz

    Muddytazz 1 ton status

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    My 203 shifter plate is a littel different:
    L Loc
    L
    N
    H
    H Loc
     
  11. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    mine too!!! /forums/images/icons/confused.gif
     
  12. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Oh damn! I was thinking about the Ford plate!!! /forums/images/icons/blush.gif /forums/images/icons/laugh.gif

    Yeah, you guys are correct on the GM plates! Ford has them how I described above. /forums/images/icons/tongue.gif
     
  13. acablik

    acablik Registered Member

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    I have decided (thanks to everyone's help) that I have a 203 t-case, possibly with the part time conversion kit. It will go ito 4 lo and 4lo lock and I can feel the added torque, but the front wheels still wont spin! I have inspected my hubs and they seem ok but they are very easy to turn--almost too easy. How can I determine if my hubs are the problem and not the t-case chain??? Thanks for your help and patience. I cant wait to take this beast off road!! By the way what is the difference between 4lo and 4 lo loc?
     
  14. NoSmog73

    NoSmog73 1/2 ton status

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    Lock the front hubs with it in 4 lock and then try to turn the front shaft right behind the brakes if one side spins and the other doesn't then the hub that is spinning is bad ...Someone will correct me if I am wrong
    And the diff with the 4lo and the 4lo lc is the 4 lo is like a limited slip and 4lo lock is just that power is sent to front and rear equally 50/50
     
  15. acablik

    acablik Registered Member

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    Ill give that a try in the morning.
     
  16. acablik

    acablik Registered Member

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    I went to the 4wheel parts store and they told me my hubs were shot. So i bought a set of warns from them and put them in. That was not the problem. How can you tell if it is the axle rather that the t-case?
     
  17. 70~K5

    70~K5 1/2 ton status

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    acablik fill in your profile. Maybe one of us is close and can help you with this.
     
  18. thatK30guy

    thatK30guy 1 ton status Premium Member

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    There's your first mistake....you listened to 4 Wheel Parts and they suckered you into buying something you didn't need. /forums/images/icons/frown.gif /forums/images/icons/mad.gif
     
  19. acablik

    acablik Registered Member

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    Yep, I should have known.
     
  20. NoSmog73

    NoSmog73 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    That was not the problem. How can you tell if it is the axle rather that the t-case?

    [/ QUOTE ]

    Try this with it in high and the hubs unlocked then you should be able to turn the front drive shaft, Then engage the hubs and the shaft should not turn on you..
    Also try this put the blazer in park and engage the hubs then move the shift lever all the to the top might be hard just use a little juice (pull off the rubber boot too - because you can see that way if the shaft is turning or not)and hop in and start moving a little and look through the hole to see if the shaft is turning..then unlock the hubs and get back in and the shaft shouldn't turn then....mike /forums/images/icons/smile.gif
     

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