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Rebuild NP203 or replace with NP205

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BAMA74K5, Apr 18, 2000.

  1. BAMA74K5

    BAMA74K5 Registered Member

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    I own a '74 K5 with 350/TH350/NP203. The guy I bought it from said the 4X4 does not work, but I do not know for sure because it does not run yet. My question is should I rebuild the NP203 or replace it with a NP205. I have read that the NP205 is a better unit, but I would like to know everyone's opinion. If I do decide to rebuild the NP203, were is the best place to buy a kit? Also, were can I find the kit that changes the NP203 from full-time to part-time 4X4? Any information will be very helpful.
     
  2. Bigd

    Bigd 1/2 ton status

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    If you have the money to redue the driveshafts.Don't waste the money on the 203.The 205 is a much better case cast iron all gear no chains.Hey they used it in 1-tons what can you say.But it all depends on how much you wheel it.Might cost the same after you have the 203 rebuilt and install a part-time kit.
     
  3. BAMA74K5

    BAMA74K5 Registered Member

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    Will I have to change my driveshafts if I put in a NP205? How much will it cost to put in a NP205?
     
  4. Bigd

    Bigd 1/2 ton status

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    I'm pretty sure you will have to change the driveshafts.I can't remember but i think the 203 has a slip tail shaft.If not i know its longer then the 205 so you'll need a longer one in the rear.Not sure about the front.I had a drive shaft built for 200 bucks.You can usually find a good deal on the tranfer cases make sure you get one for the t350 or you'll have to buy a adapter.
     
  5. BAMA74K5

    BAMA74K5 Registered Member

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    If I have to replace my driveshafts I think I will just rebuild my NP203 and put the part-time kit on it. Does anyone know if the '74 had manual locking hubs, because mine does. Since it does have the manual locking hubs, do I need the part-time kit? Please Help!
     
  6. BurbinOR

    BurbinOR 3/4 ton status

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    Ya know, I have been reading all sorts of boards for about a year, and keep seeing this "inferiority" issue with Np 203's. Gotta tell ya, seems I see more problems with 205's than the 203's. And from personal experience (5 K5's), NEVER have I had a problem with a 203, including one that was behind a beast of a 454 motor. Yep, I know the "popular" opinion is to go with a 205 but seems it isn't really justified. Just my $.02.

    '79 - 406 w/IROC TPI - K5#5 - a <font color=orange>sickness[​IMG] <font color=blue>you never get enough of!! [​IMG]
     
  7. Bigd

    Bigd 1/2 ton status

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    What kind of problems have you had with 205's.I've seen two 203's get destroyed in the same truck.It also depends greatly on driving style,and conditions too i guess.
     
  8. mudfanatic

    mudfanatic 1/2 ton status

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    I've gotta agree with blazinOR, I have seen a lot of 203's be just fine behind all kinds of engines and front bearing failures in 2 NP 205's over the years.
    Now, get your rig running, make sure the adjustments are set right on the transfercase linkage and see if the case works. It probably will work, not very many people know how to set the linkage and believe it or not the lock nuts will loosen due to vibration over the years.
    '77 K5

    <font color=red>mudfanatic</font color=red>[​IMG]
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    205 is a great case but good luck finding one that will bolt to the TH350. I run a 203 in both my 75 and 79 and other than a problem with a part time kit I have never had an ounce of trouble out of them. Lets put it this way. the 203 is still stronger than anything new out there including the Hummer case, with the exception of maybe the Atlas. 203 has gotten a bad rap. Its a tough case and will take plenty of punishment. The 203 is FIXED yoke. They never came with a slip yoke but the late 80's 205 were available with a slip yoke. Now really all that wears out in the 203 is the chain. You can get them all day long for $90 and as long as you keep the case with good oil they will last. I need to change the chain in my 75. Gosh after 200+k of full time operation it is getting loose. $90 for 200k is peanuts. I'll slap some new seals in it at the same time and I will be in my grave before it need any other work.
    Converting is another thing. Converting them leads to more failures than anything. Oil slinging off the chain is used to lubricate the case. You loose that when converted when in 2wd. It's the major cause of failure. Once converted you have to put the case in lock and get the front output spinning. the recomended schedual is every 200 miles drive 10 in lock. Personaly on my 75 that is my trail truck I have decided to leave it full time. It just felt to good in the snow on trail one at Tellico! all the Jeeps were sliding all over the place and my K5 was PLANTED and pulling good. I have also found that with monster truck driving style (when in doubt floor it) that you can get the full time truck to out handle the part time. My 79 is converted on 31 BFG AT's no lift. My 75 is on 32 BFG muds on a 4 inch lift and with the full time I can pull a corner much better in the 75. So much so I like scaring the pajesus out of little Rice boy punks in hondas by filling their rearveiw mirrors full of winch bumper and expanded steel grill on some curvy road in my area. It it rough on front tires but it's a trade off. If you do decide to go part time there is only one kit I would recomend. Mile Marker. They make 2 one is a set of tabs that locks out the center diff it's ok but over time they develop slop. Thats whats in my 79. Mile Marker also makes a better unit that replaces the whole output shaft assembly with a solid unit. For heavy off roading thats the one to get. I'm going to swap one in my 79 this summer because the beating of the shift kit in that truck as taken it toll on the cheap part time kit. That truck will rarely see a trail again. It's the wifes and she want me to pretty it up :) her idea of Pretty is a new black paint job, Mid 80's front clip with a phantom grill, NO CHROME except the polished grill and a set of monster bumper. God I know I married the right woman!

    Diging it in the dirt with my K5's
    Grim-Reaper
     
  10. Burt4x4

    Burt4x4 3/4 ton status

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    Grim, I am still gelous your wife loves K5s as much as you!
    My wife is a true city-slicker and wants a fancy car or dare I say it a preety SUV....Ouch that hurt.[​IMG].
    I almost had her convinced once she NEEDED a K5, but for only a few minnuts and she was back on the city wagon deal!!
    Later...........

    Rock ON![​IMG] 72 K5 [​IMG]
     
  11. laketex

    laketex 3/4 ton status

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    fulltime with hubs?

    Grim, got one for ya. I've got two axles and an NP203 I'm rebuilding. I've heard that you can add lockout hubs (to facilitate my detroit front) and not convert the case. That this will allow the front axle to disengage, but the driveshaft still turns, and what else? I mean, what all turns before it gets to the hubs? I would assume everything including shafts till the hubs? Reasons for not converting the case include money, wanting to keep a 2wd Low, and the problems I've seen associated with converting. My overall setup on drivetrain will be:

    Dana 44 front, new bearings and seals, 4.11, Detroit, Warn Premiums
    14 Bolt rear, new bearings and seals, 4.10, Detroit
    355 engine, rebuilt, approx 340 hp
    TH350 tranny, rebuilt
    NP203 case, rebuilt, new chain
    other stuff>>> 4" lift, 36" swampers....

    upshot, do you think I'll have a problem with an unconverted case? My truck is mainly a trail truck, some minor street driving, but mostly trails and cruising. I have a pickup for long hauls. Thanks

    Bryan


    [​IMG][​IMG]
    Durant, Ok
    '79 Blazer in progress
     
  12. blazer72

    blazer72 1/2 ton status

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    The only reson to got to a part time kit is gas milage anyway! If you do a lot of off road the stay with the 203 you have! Now if you are going to go with the 205 then call ORD and get the kit to bolt the 205 to the back off the 203 reduton gear case, and really get a low low (4to1) when needed, as for the atlas it will not handel the tork in any way like the 203 or the 205, by the way the 203 and 205 shair alot of the same bearings and even one gear, both were oem in up to 1 ton trucks, I f you wanted part time you got the 205 full time then the 203.
     
  13. ken

    ken 1/2 ton status

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    Save your money...the 203 is just fine. 203s were ALSO used in one ton trucks, so they are PLENTY strong. Look at the GM trucks of the 80s...all running ALUMINUM 208s and 241s...HELLO!!!! I sure think the 203s cast iron case is just a bit stronger than frigging aluminum...HELLO!!! Also, the chain of a 203 is 2-3 times thicker in width than a 208 or 241..that means it's STRONGER!!!!! DUH!!!! HELLO!!! IS ANYONE LISTENING?!?!??! And, a 205 will probably cost you more than $1,000 to install, after the driveshaft mods, and the adapter. Do what you want...but I'll keep my 203, heck I can even add a Doubler one day!!!

    ken
     
  14. SnakeEyes

    SnakeEyes Registered Member

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    I've got a 79 1 ton, a real 1 ton, crewcab running a built 454 in front of a TH400 and a 203 with a parttime kit and manual hubs. I tow a 30'X8' stock trailer with 4 horses to 11000 feet every year to go elk hunting. Ain't broke yet. Why buy a 205??
     
  15. ken

    ken 1/2 ton status

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    Why buy a 205?? Cause it's the "flavor of the month"!!! Just like NV4500 trannys are to Jeepers!!!

    ken
     
  16. blazer72

    blazer72 1/2 ton status

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    Hey some of us run 4500 in K5 too!
     
  17. Blazer1970

    Blazer1970 1/2 ton status

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    I agree with the "keep the 203" crowd. People pay a lot of good money to get full time four wheel drive in new trucks and SUVs. It is a cool feature for snow and slippery roads. Forget the part time conversion.

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     
  18. BAMA74K5

    BAMA74K5 Registered Member

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    Thanks to everyone for the great input. After reading everyone's opinion, I think I will just stay with the 203. I like the security of full-time 4X4. I would like to add that this is a wonderful site and that everyone is very helpful. Thanks again for the input.
     
  19. Eric78K5

    Eric78K5 1/2 ton status

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    Just in case anyone's interested....the 203 has something like a 2.00 ratio, which is higher(lower) than the 205, so it pulls better off-road. My 78 has 198,000 miles on it, and the guy I got it from said the seals on the transfer case have been shot for over 90,000 of those miles. There is very little oil in the transfer case, and when I fill it, it all leaks out. I know that I have to replace the seals, but I'd like to see someone with a 205 try running it without oil for a little while. I think that says alot about the 203. But maybe not about his mechanical skill..LOL. The seals and chain on next on my attention list.
     
  20. EDdaTREE

    EDdaTREE 1/2 ton status

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    WHAT!? Nobody knows the best thing about a 203? There's so damn mamy of 'em out there that you can almost get 'em for free.Last time I bought a tranny , the guy threw in the 203 in for free rather than unbolt it!
     

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