TH350 problems

Discussion in 'Automatic Transmission' started by Clinton Schroeder, May 16, 2018.

  1. Clinton Schroeder

    Clinton Schroeder Junior Member

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    First Name:
    Clint
    Truck Year:
    1984
    Truck Model:
    C10
    Engine Size:
    350
    Hey everyone!

    Excuse this as my first post, but I'm having issues and was hoping to find an answer here.

    I recently picked up an 1984 C10 with a "freshly built" TH350 and a bad motor. The transmission leaks a drop every 15 seconds or so from the tailshaft, so I'm already guessing it wasn't done right. But, I just finished dropping in a healthy new 350 and when I went for my first drive the truck wouldn't move. Cycling through all gears I get no engagement at all anywhere.

    I've done some troubleshooting already. This included filling to full (and later past full in frustration), making sure the flexplate was bolted to the torque converter, and cracking the cooler line to check for pressure (it has tons). After launching about a quart of ATF into my engine bay in about 5 seconds from the line I cracked to check pressure I added a pint of ATF at a time, stopping to cycle the engine through all the gears 10 seconds a piece and then retrying. No joy.

    My driveway is on a good incline which has the truck slowly working it's way towards the street, but I can tell the parking pawl is working fine, so I don't think the linkage is messed up. But, can you guys give me any ideas about what to check next? I'm seriously about to have it towed to a shop to have it worked on and I'd like to head this off before that has to happen.

    Thanks in advance,
    -Clint
     
  2. Charlie

    Charlie Full Access Member

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    Truck Year:
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    Cheyenne 10 LWB
    Engine Size:
    350/TH350/AC/4 BBL Quadrajet
    :welcome:
     
  3. Obwonkonobe

    Obwonkonobe Full Access Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    350
    Your drip from the tailshaft is pretty common. On mine I replaced my tailshaft seal 4 times with no luck. It may also be from the "weep hole" in the yoke though, Google it and you'll see. You can get a new yoke or just give it a bead of weld, maybe jb if you can't weld.

    As for it not moving, check reverse. I beat the snot out of my 350 and had the same problem. Pump was perfect, but no forward gears. Although if its an issue with the FORWARD clutches, I'd check reverse, thankfully I still had reverse to back into my garage.

    If no luck with reverse, I'd try a new torque converter, the outer housing of the converter only drives the pump and some fins in the converter, theres another splined bit inside the converter that drives the actual input shaft, and if the converter slips, you won't get any movement.

    Hope this helps
     
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  4. Derrick

    Derrick Full Access Member

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    :welcome:
     
  5. Clinton Schroeder

    Clinton Schroeder Junior Member

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    What would it mean if I still have reverse going on?
     
  6. Obwonkonobe

    Obwonkonobe Full Access Member

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    That means that the problem is with your clutches inside the trans. If you have no reverse I'd be happy, you may just need a torque converter
     
  7. Clinton Schroeder

    Clinton Schroeder Junior Member

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    That's gonna be fun news to break to the wife :slap:
     
  8. Clinton Schroeder

    Clinton Schroeder Junior Member

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    Engine Size:
    350
    Update: the truck ended up being towed to a shop to be looked at. The final verdict was that a standard turbo 350 torque converter was in there, and that it tore up the front pump. New TQ and new pump has it back on the road.

    Thanks for the help guys!
     
  9. HotRodPC

    HotRodPC Administrator Staff Member

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    OK, so what you're saying is, the newer transmission was a lock up converter Th350C unit. Yep, that'll do it.
     

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