Dual Range Hydramatic Troubleshooting

longlivelance
longlivelance Member
in "How To" - Skills, mechanical and other wise

I’m troubleshooting a hydramatic transmission I had rebuilt with the rebuilder right now. After installing it the car only barely crept forward in all gears including neutral and reverse. Below are the steps I’ve taken:


  • Ran line pressure at the test port between the band adjustment screws and am getting zero pressure and the port is dry. I even tried cranking the engine with it open and no fluid. 
  • After seeing that I wanted to verify my front pump was working and make sure the pressure regulator wasn’t sticking so I removed the pressure regulator and cranked the engine for a few seconds. Lots of fluid came out there. So it seems the pump is working. 
  • I reinstalled the pressure regulator to try a line pressure test again hoping maybe the regulator wasn’t stuck. And am still getting zero pressure at the test port. 


The rebuilder is researching to see what they can find as am I. 


Has anyone had similar symptoms and if so, what was the cause? Any insight or advice is much appreciated.

Comments

  • atc
    atc Member

    Sorry for the delayed reply. These symptoms are really surprising to me.

    It sounds almost as if something just wasn't hooked up right in the rebuild. I can't say for certain. Is there a clunk or a lurch when you put it in gear? If you do a band adjustment can you feel the rpms rising or dipping as you grip the drums?

  • longlivelance
    longlivelance Member

    I’ve been on the road and kissed this reply. The cut lurches forward in all gears including neutral. I haven’t tried band adjustments yet. Ive never worked on a transmission before so this is all learning for me. Since everything is already in the car and hooked up I am going to open the side panel and see if anything looks at odds or stuck.


    it did grind a couple times when shifting between gears when the wheels were off the ground so it seems like it is at least trying to get in gear


    The person who rebuilt it teaches rebuilds at a college and has done them before. So hoping he didn’t miss something obvious.


    One thing really baffling me is the pressure regulator port is gushing fluid when open. But the pressure test port is bone dry so fluid isn’t getting there.


    I’m really at a loss. Hoping to have the builder come down here to look at it and resolve it. It was a lot of work getting it in and everything hooked back up. It would be a shame to have e to h don’t all again.

  • ratlee2
    ratlee2 Expert Adviser

    I would recommend reaching out to Don Chase from Omaha, NE. His name frequently comes up in the discussion of rebuilding Hydramatics. He should be listed in the club roster.

  • longlivelance
    longlivelance Member

    I did speak with Don this week and he pointed me to a potential issue with the check ball valve in the feed to the rear pump that runs through the front servo.


    He says if that is missing or installed incorrectly the fluid would just be dumping back to the rear and could create my exact symptoms.


    Planning on draining and dropping the pan this weekend to get a better look. I’ll report back but wanted to share the information for anyone else in the future potentially going through something similar.

  • longlivelance
    longlivelance Member

    The check ball valve and spring were all present and installed in the correct order. My next line of thinking is the main line exhaust valve. Looking up into it the sleeve, I can see it is cocked and not square at the edge of the bore. The manual does explicitly call out the sleeve being driven too far into the bore as a potential cause for the issues I’ve been having by not allowing the valve to fully close. Being this is my first time inside one of these transmissions, I’m not sure what this should look like in a proper install. I’m including a photo in case anyone can tell me if that looks off or is how these are normally installed?


    IMG_5788.jpeg


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