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WTF fluid goes in a 203?!?!?!?!?!? ATF, gear oil or motor oil????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by dawson444, Jan 19, 2002.

  1. dawson444

    dawson444 1/2 ton status

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    What do I fill up my 203 with? I have heard ATF, gear oil, or motor oil. Which one is it? What are all you guy's opinions?

    Dawson
    Raleigh, NC

    88 K5, 6" lift, 36" TSL Radials, 14 Bolt, Rancho 9012s
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Motor oil...

    Rene

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  3. BurbinOR

    BurbinOR 3/4 ton status

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    As Road Trip Rene said............moto oil..........'tis true.

    <font color=blue>'79 ONE TON TPI K5 - See it at---&gt;<a target="_blank" href=http://www.blazzinor.rockcrawler.com/>BlazzinOR's Beast Buildup</a>
     
  4. Greenblazer-AZ

    Greenblazer-AZ 1/2 ton status

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    I read somewhere that gear oil should be used if you have a part time kit. Is this incorrect and if so should I drain the gear oil and use motor oil?

    If you knew the truth, you too would be against marijuana prohibition!
    Blue '74 K5 Blazer Topless W/ 35 BFG Muds (See profile for pics)
     
  5. m j

    m j 1/2 ton status

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    why?
    is the gear oil too thick for the little pump that feed pocket bearings? or for the chain? or what?
    what about that nice thin synthetic gear oil.

    formerly 77chev
    still a jerk though
     
  6. Jonathan

    Jonathan 1/2 ton status

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    I think gear oil is too thick for the chain and I read somewhere (here, I think) that ATF eats up the iron that the case is made of. I use non-detergent straight 30 weight motor oil cause that's what the guy at napa told me his book said, he told me the detergent in regular motor oil causes the chain to strech easier.

    77 Blazer, 350, NP203, K&N, 31-inch Cooper Discoverers
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  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    MJ, I'm not sure of the reasons behind the motor oil, I just recall seeing it as 'required' lubricant in my service manual.

    This might actually be a good question to ask in the ORD forum...

    Rene

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  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Motor oil. Same flavor you run in your engine is fine. The reason is the pump in the tail shaft. Gear oil gets thcik when cold and the pump is plastic. it can break the vanes off. It als flows better into the chain. ATF is not really that bad for them so I wouldn't worry that ATF has damaged it but Motor oil is what was spec for it. Multigrade will befine also. Multi grade was not common when the case was designed is why you don't normaly find any refference to it. I run 10W40 in mine. I figure it deals better with the cold that a straight 40 would so pretty safe year round in my climate.

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  9. 82TOYLB

    82TOYLB Registered Member

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    Manual calls for 30 wt. motor oil. I have heard that the chain will heat up more with a heavier wt. oil and cause premature stretching. Don't know if it is true, just what I have heard. My 203 has run 130k miles with 30 wt. in it for all the miles and it still runs great with no rebuild. Part time kit has been in it since 120k.

    82 Toy LB with Marlin, locked, 36's,38's,35's depending on month/mood. 79 K5 with 3/4 ton running gear, 36's.
     
  10. k5king

    k5king 1/2 ton status

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    ok,,this will show you how much i have studdied my 203 on my truck,,or any other for that fact.......
    i thought there was NO chain in a 203,,that it was ALL gear driven and that the 208 was the chain drive.
    and my 203 had gear oil in it,,my 208 i had,,had tranny fluid in it,,and my 205 has 20w50 motor oil in it.( had them all tested)all were on auto trannies.
    eblighten me oh great one [​IMG]

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  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    203 is chain...a REAL BIG chain. it runs motor oil. Gear oil is not good for these because of the pump. If your running a doubler I believe gear oil will be find in the reduction box.
    205 is gear and gear oil is what it is supose to run not motor oil. I have heard that in real cold climates some people will run ATF in them for the winter months.
    208 runs ATF. It is also chain.


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  12. m j

    m j 1/2 ton status

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    what year did they start using plastic oil pump?
    the 74 203 sitting here is metal pump gear
    dont forget that AF was spec'd for 205 use in the newer stuff

    formerly 77chev
    still a jerk though
     
  13. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Hmmm good question. I was not aware of a metal pump. My 75 is plastic. my 79 is plastic. I have the tail shaft assembly off Waxer's 74 and it's plastic also. You sure your looking at the pump? The pump is located right behind the bearing that suports the bearing. it goes on just before the speedo gear.

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  14. m j

    m j 1/2 ton status

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    well speedo gear was toasted and unless this plastic is doing a damn fine job of looking like steel.
    maybe i will smash it with a bfh and see what it thinks?
    i was trying to find a part line to see if i could press it off when someone posted they needed a plastic one though and it wasnt apparent, not really what i meant. you would have to put pressure on the 'vanes'

    formerly 77chev
    still a jerk though<P ID="edit"><FONT class="small">Edited by m j on 01/22/02 09:11 PM.</FONT></P>
     
  15. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well I got your pictures. Sure looks steel. I recall somebody saying that mid 74 there was a change in the 203. Something about the part time kits not being the same. I think it was Waxer was told it by a shop that did some work on his. That must be why. The plastic ones come right off without any problem.

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