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79 Blazer having weird drivetrain issues!

Discussion in 'Automatic Transmission' started by My79blazer, Dec 6, 2019.

  1. My79blazer

    My79blazer Junior Member

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    Joined:
    Dec 6, 2019
    Location:
    Arkansas
    First Name:
    Daniel
    Truck Year:
    1979
    Truck Model:
    K5 Blazer
    Engine Size:
    350
    Little info first. Bought this 1979 K5 Blazer as a toy about year ago. It has a 350 with Dart Iron Eagle heads, quadrajet carb, 350turbo tranny with a NP 203 transfer case with the part-time conversion sitting on 36's and a 4" lift. It had some engine issues ( a lifter needed replaced general tune up needed) so I parked it to tinker on when I felt like it. Daily driver got repo-ed so I did the work to make it my daily driver about a month and a half ago.

    So about 2 weeks ago I was leaving the store and when I shifted from reverse to drive there was a quick ( about a sec) but loud grind noise. I assumed it was my transfer case. I only lived about 6-7 blocks ( which it drove with absolutely no noise or problems) so as soon as I got home I checked my trans fluid which was fine.

    There was a small puddle of what looked like engine oil next morning (which it does leak oil a bit from around the timing chain gasket) so I didn't think anything about it.
    I continued driving it like normal (small trips of usually less than a few miles) and it would occasionally make that small grinding it always shifting from reverse to drive.

    Here lies the true problem. I went to make a quick run to grab something to eat and got about a block from my house when it suddenly made a small grinding noise and acted like I stomped on the brakes. Besides completely freaking out my 15year old, I let it coast a bit gave it a little gas and it started forward like normal, for about 25-50 feet before doing it again. Thought it must be my transfer case that was leaking and out of fluid.
    Best way to explain it is like I shifted the transfer case from Hi to Low.
    So I put it in 4wd, locked the hubs and limped it home with no change. Pulled the plug on the transfer case to check the fluid level and it's still full.

    The transmission doesn't have a history of shifting rough or late, have whinning noises or anything other than the usual "Chevy hard shift into gear" that every chevy I ever owned did.

    Really scratching my head here on whats going on but hope someone here can point me in the right direction.
     
  2. Shorty81

    Shorty81 Baby Boomer

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    Welcome from the Buckeye State
     
  3. Frankenchevy

    Frankenchevy Supporting Member Supporting Member

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    Which transfer case do you have? Have you pulled the flywheel inspection cover yet?
     
  4. My79blazer

    My79blazer Junior Member

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    Engine Size:
    350
    It has a NP203 with the part-time conversion kit. Thought about rebuilding it back to full-time but I think I will have to go back to the slug hubs.
    Anyway, I have not pulled the cover yet but am planning on spending some time under it tomorrow so I will do that. Think it might have something to do with that?
     
  5. Frankenchevy

    Frankenchevy Supporting Member Supporting Member

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    Probably not, but it’s an easy first place to look.
     
  6. Snoots

    Snoots Supporting Member Supporting Member

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    First Name:
    Roger
    Truck Year:
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    Truck Model:
    Jimmy Sierra
    Engine Size:
    350
    I think that's your problem.

    Welcome from Georgia welcome.gif
     
  7. My79blazer

    My79blazer Junior Member

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    Truck Year:
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    Truck Model:
    K5 Blazer
    Engine Size:
    350
    I want to rebuild it back to a stock np203 but for now I just need to get it back on the road.
     
  8. My79blazer

    My79blazer Junior Member

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    First Name:
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    Truck Year:
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    Truck Model:
    K5 Blazer
    Engine Size:
    350
    °Update° did a transmission filter and fluid replacement as well as replaced the modulator today and checked all vacuum lines and did a visual inspection the flex plate without removing the transmission or anything and everything looked fine. Found a small vacuum leak and repaired it ( truck idles a lot smoother cold now) but when I test drove it I got 2 driveways away before grinding and slowing down again. Gonna check the governor and see about borrowing a pair of stands with a higher setting to check the differentials and unhook and reinstall the transfer case shift linkage tomorrow but I am not holding out much hope.

    Just figures that I might need a tranny rebuild but the kids Christmas comes first so I might be borrowing rides until after the new year if I cant figure this out.
     
  9. dvdswan

    dvdswan Full Access Member

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    First Name:
    Dave
    Truck Year:
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    Truck Model:
    K10
    Engine Size:
    350
    Welcome to the site.

    Kind of sounds like a loose chain in the t/case. I would keep it 2wd conversion kit in though, unless that's trashed.
     

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