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Technical Turbo 400 question

Discussion in 'The Hokey Ass Message Board' started by Peelout30, Jul 21, 2021.

  1. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    Brought a new project 1966 c10 home. Has 350/turbo 400 in it. Needed brakework so I salvaged a booster out of 84 k10 and put together to drive. During the drive it would shift from 1st to second fine but wants to down shift back to first . I checked vacuum to the modulator and its good, the modulator appears to have been changed at some point so I pulled the governor. I noticed the valve would move up but sometimes would stick up and not fall down. So I pulled it apart to clean it and noticed the weights and springs are different on either side. Looks like someone used what they had left in a kit. I weighed the wings with weights/springs and they are only a gram different. My question is with different style weights and different springs will this cause shift problems even though they weigh similar?


    thank you
     

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  2. squirrel
    Joined: Sep 23, 2004
    Posts: 49,794

    squirrel
    Member

    probably was built that way originally. if you post close up pics of the crimp on the pins, we can probably tell whether or not it's been worked on.

    I expect your problem is somewhere else. Usually the only thing wrong with a governor on a GM trans is that the plastic gear will break, and it won't upshift at all.
     
  3. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    The pins are not crimped at all. They have indents with clips, which leads me to believe the governor was worked on. I thought all pins were crimped from the factory, I could be wrong though.

    thanks
     
  4. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,450

    Elcohaulic
    Member

    Try disconnecting the down shift solenoid and see if it shifts ok. If it does, the solenoid needs replaced or cleaned.

    Pull the vacuum modulator out and see if it holds vacuum.
     
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  5. saltflats
    Joined: Aug 14, 2007
    Posts: 10,929

    saltflats
    Member
    from Missouri

    What speed does it shift into second?
    If it is at what you would call normal road speed than the governor is not the problem.
     
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  6. jaracer
    Joined: Oct 4, 2008
    Posts: 1,220

    jaracer
    Member

    Like Squirrel said, the different springs are probably stock. The light spring gives you some pressure at lower speed and the heavier spring controls the pressure at higher vehicle speed.

    Does it ever shift to high gear? Does the engine have low vacuum? Does reverse work okay? Answer those questions and I can give you direction to explore.
     
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  7. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    I’m getting almost 20 of vacuum at the engine, reverse works fine no issues with that at all, it did not seem to want to shift to third just back to first I didn’t drive it long not wanting to burn anything up
     
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  8. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    Also the downshift solenoid was already disconnected
     
  9. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,809

    greybeard360
    Member

    Was the solenoid or switch disconnected? Switch is on the gas pedal, solenoid is in the trans. Either way, the solenoid or valve could be stuck in the downshift position. since you have reverse the direct clutch is working.... that points to the kickdown valve.
     
  10. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,450

    Elcohaulic
    Member

    I would be pulling the pan on that Turbo and taking a look at the solenoid. I had one that was floating around in there. When it fell off the trans would not shift unless I was really cranking it up..
     
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  11. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    I checked and No switch was installed by previous owner, no wire leading back to the solenoid
     
  12. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    Thanks you guys are a major help!!! I will start to install switch and checking the solenoid function, much appreciated
     
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  13. squirrel
    Joined: Sep 23, 2004
    Posts: 49,794

    squirrel
    Member

    you don't need to wire the solenoid. But you do need the solenoid to be in place, as it blocks a hydraulic port (except when it's engaged, and you are kicking down)
     
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  14. jaracer
    Joined: Oct 4, 2008
    Posts: 1,220

    jaracer
    Member

    If reverse works that means the high/reverse clutch is good. However, this clutch piston has 3 seals on it giving two apply areas. In reverse fluid is sent to the whole of the piston for good holding power. In high gear a smaller area is used. If the center seal is bad or installed backwards you will have a good reverse and no high gear or a severely slipping high gear.

    Good vacuum to the modulator should give you normal upshifts. You should be able to get in high gear at light throttle before 30 mph.

    The fact that it wants to go back to first makes me think something like the kickdown solenoid is delaying the shift (as others have mentioned), or governor pressure is very low. If you drop the pan and find the kickdown solenoif to be okay, take a good look at the governor bore in the case. Sometimes these get scored and leak off governor pressure.
     
  15. VOETOM
    Joined: Aug 6, 2006
    Posts: 287

    VOETOM
    Member
    from MO

    Peelout, I see the weights from the Superior or Coan governor kit in it. It will shift higher at WOT than it would with stock weights. The springs, like others said, will affect the low speed, light throttle shifts.
     
  16. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    Ok, here is what I found. Aftermarket solenoid with pinched wire, also when I removed it the shim fell out. I watched a guy on YouTube (YouTube.... I know, I know) say not to use the shim with aftermarket. When I got the solenoid on the bench the shim does not line up correctly with the top of solenoid, will this cause problems? I also attached a pic of the pan had sludge in the bottom and filter not sure what amount of sludge is ok. Thanks again
     

    Attached Files:

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  17. squirrel
    Joined: Sep 23, 2004
    Posts: 49,794

    squirrel
    Member

    that is the later style solenoid, with a rubber seal built in, it should not have the metal gasket. Make sure there's no dirt in the orifice in the solenoid, keeping the needle from closing all the way.

    If the sludge is fine powdery stuff, it's probably normal wear. If there are strange chunks of metal or fiber, then things are coming apart.
     
  18. Peelout30
    Joined: May 24, 2008
    Posts: 151

    Peelout30
    Member
    from Missouri

    Want to thank everyone again for their help. Not sure exactly what did it, but I dropped the pan replaced the kick down solenoid, vacuum modulator , filter and had a good drive. :)
     
  19. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 2,450

    Elcohaulic
    Member

    The victory drive is one of the best highs I ever experienced!

    I always liked the way the TH-400 shifted, like a fine time piece. They were lighter then the transmissions they replaced except for the Slim Jim.. I use the Trans-Go shift kit.. This allows me to have more control over the gear selection..
    The Hurst Auto-Stick 1 shifter seems like it was built for the TH-400. It has very positive gates and looks just like a four speed. The mechanical linkage gives the driver excellent control over shifting..
     

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    Last edited: Aug 8, 2021
    kadillackid and Hot Rod Nut like this.

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