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TH400-zero line pressure at test port?

Discussion in 'The Garage' started by ducttape114, Oct 23, 2004.

  1. ducttape114

    ducttape114 1/2 ton status

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    here goes.....
    brand new rebuild with full manual valve body. reverse and third not working. reverse remains in neutral. third remains in second. when we went to check the pressure the gauge didnt even register in any gear. thoughts anyone? thanks
     
  2. Nonesuch

    Nonesuch 1/2 ton status

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    who's valve body are you using?
     
  3. ducttape114

    ducttape114 1/2 ton status

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    art carr reverse pattern, full manual valve body, with compresion braking.
     
  4. Nonesuch

    Nonesuch 1/2 ton status

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    I had some serious problems when I installed mine (I have the same one) It turned out to be a defective valve body.


    Did you pull the sealing ring off of the center support inside the transmission? Did you replace the pump spring? Did you pull the seals off of the rear servo piston? Is your front servo piston flat on top(part on the valve body, looks like an upside down cup)?


    There is also one other mod you can do. Remove the center seal on the direct clutch drum and plug the port to the right of the center support bolt (ie, if looking north and the bell housing is pointed north). I use a 7/16" expansion plug (freeze plug) and beat it in the hole. This provides more pressure to the direct clutch pack for reverse and third
     
  5. jac6695

    jac6695 1/2 ton status

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    I know Toby (moneypit) tried one and could not get it to work right at all just before Blazer Bash. He had a similar problem with the lack of third gear. There is something wrong with that design, and as far as we know, isn't made anymore. I would put your stock valve body before you change so much, you can't go back. /forums/images/graemlins/frown.gif
     
  6. jac6695

    jac6695 1/2 ton status

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    BTW, I have heard that TCI just came out with one that has compression braking, and sounds like it is much better.
     
  7. ducttape114

    ducttape114 1/2 ton status

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    i dont think its the valve body because i had the same one in the previous tranny. i had sombody else build the tranny this time so i cant be positive, but i did give him the instructions so i think he got the ring. i know the servo piston is right cuz i had to search all arounf to find the right one the first time. the thing that really throws me is that there is no pressure in ANY gear. even thou first and third are working fine.

    cool trick with the freeze plug, i will do that next time im in there.
     
  8. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    hey dood. whatssup...

    You probably stuck the pressure gauge on the governor pressure port... towards the back of the tranny.. the only time you'll see governor pressure rise is when road speed increases.. (governor pressure overcomes the 1-2 and 2-3 shift valves to make your shifts)..
    The line pressure port is on the drivers side middle of the tranny.

    Also when i installed my tci reverse manual valve body in my th400, you had to install a ball bearing, pounding it into the case to plug the passageway for the reverse accumulator.. if you already installed it in the last tranny, you couldn't have removed it to put it in this one. /forums/images/graemlins/thinking.gif
    Also you must remove one of the seals on the center support. I believe it is the 3rd one back that you take out.. the first and second seals are sealing the direct clutches. so hopefully the correct seal was removed!--->
    ..As for no reverse or third...
    Reverse uses the direct clutches and the rear band. Manual Low 1st gear also uses the rear band. If you pull the shifter down to 1st gear and you have engine braking when you let off the gas, you know the rear band is working.
    To make the shift from 2nd to 3rd it applies the direct clutches.
    So i hate to say it but the thing in common between no reverse and no third is the direct clutches aren't engaging like a seal is blown or they're toast.
    I'd be willing to bet ya $20 something is up with your direct clutches (not applying).
     
  9. Nonesuch

    Nonesuch 1/2 ton status

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    BTW, I had a similar problem with my first Art Carr 14006(no 2nd or reverse). The thing that was wrong with it, a pin for one of the shift valves was not installed and it was blowing fluid around the port for the direct clutches. Their manufaturing mistake smoked my freshly rebuilt tranny. /forums/images/graemlins/angryfire.gif They replaced the VB for me and I fixed everything back up but damn that company pissed me off.

    You may want to check if all the valves are pinned in their bores too. I would look at all the easy stuff before pulling the trans and making sure the guy that built it removed the proper seals.

    Here is a link to the instructions. The correct sealing ring to remove from the center support is the second one down from the top (looking down into transmission).

    http://artcarr.com/instructions/documents/14006.pdf

    I would go by yourself this book and just start doing your own transmission work. It is not that hard and you can do it with tools everyone has in their garage.
     
  10. ducttape114

    ducttape114 1/2 ton status

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    hey ryan! hows it going?

    i got the gauge in the right port. i had my buddies text book.
    i dont have the governer gear in there, but that shouldnt matter according to my tranny guy.
    its the same case i had last time but i dont remember hammering a BB anywhere, and it worked before.
    he had the instructions from art carr so i hope i left the proper seal out, but thats a posibility.
    i guess the best thing to do is buy the book (just ordered it) and drop her back out and go through her. i was really considering just having him build a plain old factory replacement then doing the VB myself. next time i guess. thanks for the advice guys.
     

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