TH350 won't shift to 3rd and late shifts 1st to 2nd

Discussion in 'The "Juice Box"' started by nick21, Oct 28, 2017.

  1. nick21

    nick21 Active Member


    I need some help diagnosing my issue. The transmission operated fine before removing it. The original issue was a leaky pump seal (o-ring). I removed the transmission and replaced the pump seal and gasket. During the installation I also installed a new torque converter and u-joints. Now here is the issue...

    Issue: Under light acceleration the transmission shifts from 1st to 2nd around 2800 rpm and it won't shift to 3rd at all. At 55mph it is taching 3ooorpm. It also slips in 1st and 2nd under light acceleration. But at WOT the car pulls hard in 1st and 2nd. If I manually shift the car from 1st to 2nd it takes about 3 or 4 seconds for it to actually shift.

    What I've tried: Checked the fluid and it is full/ Ran a new vacuum line to govenor/Disconnected the kickdown cable

    Here is the link to the torque converter

    Any help is appreciated. Thanks in advance.

    Thanks, Nick
    Last edited: Oct 28, 2017
  2. 8ad-f85

    8ad-f85 Well-Known Member

    Is the new vacuum line all rubber by chance?
    What was the effect or purpose of disconnecting the kickdown cable?
    Did you leave it that way?
    When you shift manually, is it up-shifting at the normal full throttle rpm as before?
  3. 68vert

    68vert New Member

    Check the downshift valve. Sounds like it’s stuck in position making the trans act like it’s in passing/downshift mode.
    8ad-f85 likes this.
  4. Matt Knutson

    Matt Knutson Well-Known Member

    Do you have any updates on the problem?
  5. gstewart

    gstewart Well-Known Member

    U must to have kickdown cable attached and adjusted properly. Have u tried adjusting the modulator valve? Does not sound like a torque converter problem.
    8ad-f85 likes this.

Share This Page