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t-case fluid and U joints

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky, Aug 20, 2000.

  1. Sparky

    Sparky 1/2 ton status

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    First of all, this site rules. I'm new to it, and it is nice to know so many people share my passion for Blazers.

    Ok, Here are my questions. I got a 78 k-5 with what I beleive is a NP 203. I know that is what the truck came with, but I am not sure that is what is in it now. I am susspicious because the SB 400 was swaped for a 350, and that makes me wonder what else was done to it. How can you identify the NP 203 compared to other cases? I need to know so I know what kind of fluid to add. I think the previous owner might have put ATF instead of 10w 30.

    My second question involves a knocking noise. When I hit the gas hard, espesialy while turning, there is a loud knock. I know this can occur with bad engine mounts, but they seem to be good. My next guess is U joints. Anyone know anything else to check?

    78 K-5
     
  2. slodawg

    slodawg 1/2 ton status

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    Welcome to the club. You know now that your here it's hard to leave. (just a warning) Ive got a 78 too. (attached pic) The Np203 has a shift pattern of loloc-lo-n-high-highloc if I remember right. That is one way to tell. Also on the front of the case their is a little metal tag that will have the type/gear ratio/date mfg. on it. Although over time these tend to get lost or hard to read. Another way is to check the linkage, if you have two rods instead of one its a 203. The 205 and 208 only have one. (im not sure about the newer t-cases) The housing on the 203 is cast metal with a rear out put shaft housing that is aluminum. On theknocking noise I would check all your u-joints. I carry a couple extra with me at all times just in case.

    <font color=blue>SLODAWG</font color=blue>
    http://www.slodawg.coloradok5.com
     
  3. titanic

    titanic 1/2 ton status

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    If you don't have lockout hubs-you have a 203. If you do,you still could have a 203 that has been converted to part time. If your motor mounts are bad-the noise you hear would occur when you hit the gas every time-turning or not.
     
  4. DMK

    DMK 1/2 ton status

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    It should have have 10-30 or 40 in it. Get the atf out. The noise may be the differencial inside the t-case. 203's have this because they are full time four wheel drive. May also be rear locker if equipped but not sure on that one. Someone correct me if wrong, thanks.
     
  5. Sparky

    Sparky 1/2 ton status

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    Thanks for the help guys.
    I know the shift pattern for the 203, but I was not sure if you could use the same linkage and shifter for a different case. As far as the hubs go, I would not put it beyond the previous owner to leave stock hubs with a part time case. He could not figure out why the truck ran some what poorly, and why it dieseled somethimes. The timeing was 8 degrees off.
    I think the knocking noise is a result of the t case mounts. The u joints all seem solid and unworn.

    If you were wondering... My truck is a 78 with a 3 inch ranco lift and some 33 bfg at's. Interieror has new carpet headliner and seats. It is currently open at both ends and has 3.42 gears :(, no cats :) and a 350. Future plans are a part time kit, rear locker, 96 or up Chevy truck seats and console. OH.. and a 700r4 that is built up since it should be used as a boat ancher otherwise.

    Sparky

    78 K-5
     
  6. 87 mid canada k5

    87 mid canada k5 1/2 ton status

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    Check your bolts on the steering box and make sure they're tight. My trucks' loosen off once in a while and it causes a loud bang when I turn the wheel.

    MIDCAN k5 " DIG A HOLE!!!"
     
  7. Executioner

    Executioner 1/2 ton status

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    The housing on the 203 is cast metal with a rear out put shaft housing that is aluminum.

    Please tell me more about this rear out put shaft that is aluminum !
    TIA
     
  8. blazer72

    blazer72 1/2 ton status

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    the 205 and 203 t cases started out with 80w90 in them, then as mileage problems started, GM went to 10w30 then ATF. A good rule is if your running a auto trany run ATF in the T-case. A 4 speed then use the 80w90. Why do this the seals between the 2 are not the best! And be for you go off on tangents about this let me say that the 80w90 is the best to run and I do have both the 203 and the 205 in my truck plus a NV4500 all useing that lovly syntec 75w90 that's 20.00 a quart from GM or dodge and it takes about 11 1/2 quart to fill every thing up!!!

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  9. slodawg

    slodawg 1/2 ton status

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    Executioner, I guess you were refering to my comment. I did not say the shaft was aluminum,I said the rear output shaft <font color=blue>HOUSING</font color=blue> is aluminum. I dont know what else you would call it. The 2 np203's i have in the garage both have'm. If that is not the correct term let me know and I'll be to sure to make a note of it.lol

    <font color=blue>SLODAWG</font color=blue>
    http://www.slodawg.coloradok5.com
     
  10. Wheels

    Wheels 1/2 ton status

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    Easy way to tell a 203 from a 205. The 205 has a round plate (about two iches in diameter) to the right of the output shaft housing with three bolts in it. The 203 doesn't.
     
  11. Sparky

    Sparky 1/2 ton status

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    hrm? Call me crazy, but I could have sworn that the np203 is supposed to use 10w 30 motor oil because it is chain driven, and the np 205 is supposed to use gear oil (80w90) becaue it is gear driven. "Blazer 72" seems to think otherwise. Anybody else have any insight on the matter?

    Sparky

    78 K-5
     
  12. blazer72

    blazer72 1/2 ton status

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    Look at the service and the rebuilder sites on this. My 72 owners book say to use 80w90 in both the 205 and the 203. Yet in an 1980 owner book it says to use atf in the 205. The only though on this is that it takes more hp to turn a T-case with 80w90 in it then atf or 10w30. If it was up to me as I said in my post I would run the best oil I could in the t-case. Which I do! SOme of us have spent years find the ins and outs to things. I would love to run something other tham the syntic that the NV4500 call for. but after seeing the way that the seal or seals work that are between the trany and the t-case I understand why there not trusted for much more than to keep the fluid from run from on w the the other. In some cases the seal is on the out side or the cuppler sleave. Ever mixed atf with 80w90 or 10w30 with atf try it some time. In some case they dont mix at all just gum up. If need be I can fax or post the info here to show you the cange in oil use over the years.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  13. Executioner

    Executioner 1/2 ton status

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    Your 72 owners book is wrong, in 72 the Np203 was not an option. The first NP203 started to show up in the
    73 model year((9/72)).

    Unless my editor copied your sentance wrong, you are saying that the extention housing on NP203 is
    Aluminiun ?
    Is this a fact, or are you stating opinion on the two units you have ?
    TIA
     
  14. blazer72

    blazer72 1/2 ton status

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    Dont know on the 203 tail shaft housing as I dont have one the 205 that I have is steal. And the 72 line assembly manuel that I have shows the install of the 205 through 72 and the 203 starting with the 72 year. Its not clear if the dana 20 was still an option in 72 still or not. It looks like the 3 speed 4 wheel drive was gone in 71 when the parts ran out would be my guess. by the way the blazer line stoped on or about the 1st of march to retool for the 73. Though there are still some vins that show that they were made in april. Just like there are some 72 blazers made with cuts in the center of the dash for speacker that only the truck had blazers had there,s dow below the dash.


    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  15. slodawg

    slodawg 1/2 ton status

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    EXECUTIONER, I believe it to be fact. Both of mine are. and all the ones I have seen are. My buddys truck is, Petersons 4wheel & offroad says they all are,(april 200 t-case inforama page 52) They call it the tail housing, same differance. On that note 205's where avail. from 69 to 73 Blazers/jimmys 73&74 jimmy's Np203 73 to 79 blazer/jimmy at least thats what I've read. Thats not even thinking about the pickups,suburbans and custom ordered trucks. I bet if you got the MONEY they'll put you one in a Tahoe,if you've got the money.

    <font color=blue>SLODAWG</font color=blue>
    http://www.slodawg.coloradok5.com
     
  16. Sparky

    Sparky 1/2 ton status

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    Slodawg,

    That is an interisting thought. Put a 203 in a Tahoe. I think the 203 was way ahead of it's time. Think about it. Subaru brags about how great and inovative their all wheel drive is. Well the good old engineers at Chevrolet have been putting all wheel drive in their trucks from 1973 to 79. Yes it is a little different, but the differintal in the transfer case is a good idea. A Tahoe with a 203 would be bad ass. All wheel drive is pretty cool. I would keep my 203 the way it is if it did not ruin my gas mileage and speed up the process of drive line destruction. Just an interisting thought.

    Sparky

    P.S. Actually, Chevy did not engineer the 203. New Process did, and it was in Dodge's and F**d's as well, but hey, I am always trying to make the good old bow ties look better.

    78 K-5
     
  17. Hey guys, I just replaced that piece (cause my dumba$$ broke it). According to the parts diagram, it was labeled as a "transfer case extension". I did hear it referred to as a shaft housing though too.
     
  18. Kelboski

    Kelboski 1/2 ton status

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    the knocking noise could be the rear end....it may need a gear oil change and new GM ADDITIVE. mine was doing this only on turns...had the oil and additive changed and that fixed it....the lack of..or old gm additive causes the knock...hope this helps
    Kelboski
     
  19. Boss

    Boss 1/2 ton status Author

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    Just want to add my two cents in about the Tcases. NP203 is not aluminum, its steel. 205 is not steel, its Cast Iron. 208 and 241 are aluminum. 203 requires Motor Oil and 205 requires Gear oil or ATF. Prefer gear though, b/c I ran both and gear oil seems to do better. ATF was too thin I think. Anyways, 208 and 241 require ATF. 73 to 79' K5's did come with 205's, only the manual ones did (SM465). The Autos (TH350) came with 203's. Yes, these are FACTS, not opinions. Except the gear oil in the 205 instead of ATF, that is my opinion that gear oil runs better in the 205 than ATF, since I did try both for a while.
    Boss

    [​IMG]
     
  20. LittlePig

    LittlePig 1/2 ton status

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    Another couple of tipoffs on 203 vs 205. First, every 205 I have seen has a shift lever made of thick round metal, usually painted black. The 203 has a chrome-plated lever (though the knobs on both look the same). Also, if you crawl under the truck, the 203 has two sections to the main case. A more or less vertical section, which houses the range gears, and a diagonal section rearward of that housing the chain drive. The 205 is all in one box. The 203 also has a large aluminum housing about the size and shape of a coffee can on the very back where the speedometer cable is attached (I think this is the differential housing, but I'm not sure). The 203 most commonly ran with 10-40W in it, though later chain drives like the 208 use ATF. 205s seemed to use 80-90W until very late, when some ran ATF also. This seems to be a mileage/startup lube issue. The thicker stuff wont circulate in the case as quickly as cold, and may affect mileage, but will protect the gears longer when hot. The thinner stuff was probably used later to help achieve mpg goals at the expense of longevity. If you have a 203, you have a very tough t-case, as long as you can stand the gas mileage hit and front end wear. As said below, the 203 was ahead of its time, not only in the idea of full-time but in the sheer scale of the case, which would not look out of place under a two-ton commercial truck.

    Email: xiaozhu@my-deja.com
    ICQ: 84108805
     

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