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I Got a 203 and want info/specs/pro/cons

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rezalb, Dec 26, 2000.

  1. rezalb

    rezalb 1/2 ton status

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    I have a np203 and wondered, well I know you guys ahve all the answers, but I want to read up up them. Pros and cons, how they work, comparisons, what breaks and so on. I guess this one has a kit that allows a part time and not full time action. Thanks in advance for your help guys .

    rezalB

    Built for a purpose.
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    What kind of info are you looking for? Its cast iron, chain driven, and uses engine oil for lube. A lot of people didn't like them because they were full time and didn't have the best street manners. I think they got a bad rap, they're actually a pretty strong case, although they are heavy. They have a 2 to 1 low range. I've never heard of one that broke but I would imagine the chain would stretch eventually.

    Rene


    [​IMG]
     
  3. Blazer79

    Blazer79 1/2 ton status

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    Mine's been running strong for more than 100K miles with no rebuilds. Not even an oil change until it got into my hands 2 years ago.

    It has LoLoc - Lo - N - Hi - HILoc positions on the shifter. An NP203 that has not been converted to part time will work like this: It's full-time 4wd when Lo or Hi is engaged a differential inside the transfer case will allow one of the driveshafts to turn faster than the other. Just like a differential inside an axle allows one wheel to turn faster than the otheras necessary. This means that if you lift one tire and chock the other three, you will be able to spin only the lifted one.

    This mode is for high-traction surfaces. It allows for different speeds on the different axles so you can turn easily on corners. The advantage is that on slippery surfaces you will get extra grip without risking losing control as 4wd mode would. I love this mode. I've even been able to drive complete trails in this mode without having any traction problems.

    If you engage LoLoc or HiLoc, the differential gets locked. it's the real 4wd mode. both driveshafts must spin at the same speed. This one is necessary when you really need all the traction you can.

    I've only found advantages to the NP203. The worst disadvantage I find is that I will someday have to change the chain, where another case would save me this cost. Also sometimes it is stubborn and will stay Locked even if you move the shifter out of the loc position. Solution: backing up a few feet will disengage it. Many people think that the full-time feature is the culprit of low mileage, so they install a part-time-kit only to discover that mileage remains just as bad as before and they spent more than $200 in a kit that removes its best feature.

    Advantages: It's as strong as an NP205 except for the chain, but then again, I've never heard of anyone who had problems with it. Traction is much better in a full-time 4wd vehicle than in a 2wd one. Why do you think they have all these fads about traction control systems on the new SUVs?

    Oh yeah, I almost forgot. it uses 30 grade engine oil. If yours is converted to part time, you should ocassionally engage 4wd mode so that the front of the NP203 gets lubed properly and avoid premature failure.

    Hope this helps. If you have more questions, just ask.

    <font color=blue>//////
    <A target="_blank" HREF=http://blazer79.coloradok5.com>http://blazer79.coloradok5.com</A>
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  4. EDdaTREE

    EDdaTREE 1/2 ton status

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    Check out OFF-ROAD.com...they have a page on the 203.

    "I'm not stuck...I'm just re-evaluating my line"
     
  5. rezalb

    rezalb 1/2 ton status

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    Thanks guys, that about sums it up. Geese, the old timer helping me felt the full time 4x4 was a negative, then he shifted and turned and said it had the part time kit. I was excited and thought it was cool, now it sounds like I should take that crap out.....
    TRustyK5, this combo, 1993 model 454 with TBI, TH400, NP203 came out of a 1979 Suburban that got tagged in the front and bent the frame. I have a 1983 K5 with a 6.2 clanker. So I purchased the complete Suburban for $3,000.00 (I thought was a good deal). Changed motors, tranny and transfercase, next will be the axels, 14boltFF and the 10 bolt front, 33" 8 lug centerlines, along with the Rancho suspension. So that was the story, I hope It is done by spring time...Thanks again for your help...
    rezalb

    Built for a purpose.
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I'm with Blazer 79. other than the chain wearing out every 150k they are pretty trouble free. I run one fulltime in my 75 and My wifes 79 has one with a part time conversion. I have had problems with the converted one because of the part time kit. Also when they are converted they do not lubricate properly. you MUST PUT IN LOC every 200 miles for about 5 miles to refill the resivior in the tail shaft that lubricates the tails shaft bearing. If you neglect to do so it will fry the bearing.
    both trucks get about the same millage. I have only 2 complaints about the full time.
    1&gt; the front tires do wear quicker and you must rotate on time.
    2. sometimes the steering feels heavy.

    Now I have run both on loose surfaces where you really didn't want to be in Loc and man the faull time works great!!!! shift in and out of LOC at anything under 45mph as long as all the tires are moving the same speed.
    If I ever get another truck with a 203 that is not coverted I won't convert it. I have seriously thought about putting the 79 back to stock.
    As for strength...not quite as strong as a 205 but stronger than anything else that came in a 1/2 ton. Just make sure you have a jack to put that heavy pig in. You don't even want to think about trying to bench press that fat pig. It's about 300lb. Take a 24in x 24in 3/4 thick peice of ply wood and build a jig that you can bolt to your jack. that is the only safe way to put that case in.

    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  7. BurbinOR

    BurbinOR 3/4 ton status

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    Well said Blazer and Grim.

    Here is a question for you............seems the "ideal" setup is the NP 203 left fulltime with maybe lockout hubs? This way you do reduce the drag on the drivetrain on those sunny dry days with no need for 4WD. Do you agree?

    <font color=orange>'79 - 406 TPI -<font color=orange> K5#5 - <font color=blue>See it at---&gt;<A target="_blank" HREF=http://www.blazzinor.coloradok5.com>http://www.blazzinor.coloradok5.com</A>
     
  8. Blazer79

    Blazer79 1/2 ton status

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    I think that setup benefits very little because you'd still have the same components turning all the time, since you'd have to engage any of the LOC positions which would turn your front driveshaft and axles. You're right about the reduced drag, but then the rear drivetrain has to come out with extra drag to move the whole 3-ton-beast by itself. Still it sounds like a good idea if you insist on having 2wd. In my case I wouldn't bother.

    <font color=blue>//////
    <A target="_blank" HREF=http://blazer79.coloradok5.com>http://blazer79.coloradok5.com</A>
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  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    You can't drive it without the part time kit with the front unlocked. The case has a open diferential in it. You unlock the front and under load all the power will go to the front axle. You don't want to drive in the LOC position at high speed. the way it locks that center diff it was never intended to be locked above 35mph. In a straight line if you keep your tries rotated you would be hard pressed to notice the full time. In corners you drive it like a monster truck. It likes to push through the corners when off the gas. Floor it and it pulls through the corners like a front drive car.
    Quite honestly since my trucks have different gear ratio's and different size tires etc I couldn't really tell if there is a difference in MPG. The 79 was converted when I bought it so I have no idea. Before I put the new motor in the 79 it got 10-11mpg on 3.73 gears. The 75 with tired motor gets about the same. When I installed the Crate in the 79 it went up to close to 14mpg.

    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  10. Eric78K5

    Eric78K5 1/2 ton status

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    I'm not an expert at the 203 or anything, but I do have two things to say that may help. First, the 203 in my 78K5 didn't have any oil in the case when I bought it. The seals were bad, and the guy said that he had driven it 40,000 miles without servicing it. I replaced the seals, and added oil, and have had no problems out of it so far. Second, like everyone else said...the 203 has mechanical technology from the 60s and 70s that everyone is installing in modern SUVs. Hope that helps.

    Eric78K5
    K5-Because Size Matters!
     
  11. rezalb

    rezalb 1/2 ton status

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    UPDATE, UPDATE, UPDATE, UPDATE...
    Thanks again for all the info, HOWEVER....the 203 is mated to a TH400 ( I dont know what year I just got it this way..OK) and the stupid adapter plate is broke, and the only ones I can find are out of state and asking price is $200.00 to $240.00.
    SO, I can get a 205 for about the same coin, give or take...
    Back to the drawing boards. WHAT TO DO? 205 or spendy adapter plate? HELP ME ......

    Built for a purpose.
     
  12. FWP

    FWP CRS

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    If it's a money thing, weld the adapter you have (assuming big chunks aren't missing). A 205 would be a nice upgrade, I would love to get my hands on a 205 for 250$[​IMG], Where did you find one at that price- send private[​IMG]- I would like dibs if you don't buy it.....

    [​IMG]
     
  13. BurbinOR

    BurbinOR 3/4 ton status

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    Thanks for the clarification Grim. Forgot about that differential thing............well, maybe a Dana 60 with the fulltime 203.........now that might be the best setup!?!?!?

    <font color=orange>'79 - 406 TPI -<font color=orange> K5#5 - <font color=blue>See it at---&gt;<A target="_blank" HREF=http://www.blazzinor.coloradok5.com>http://www.blazzinor.coloradok5.com</A>
     

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