72 Skylark, will not shift to 3rd.

Discussion in 'The "Juice Box"' started by mattd3933, Apr 15, 2020.

  1. mattd3933

    mattd3933 Member

    I have a 72 4door Lark, th350. Not running when i got the car, rebuilt the engine, a bit over 500 miles on it. I was pretty sure i didnt have 3rd gear, installed a tach. No 3rd. I had a Trans leak, and when low i had a delay shifting to reverse, 4 seconds solid. Also i have never managed to get the kickdown, detent cable hooked up.

    i recently dropped the trans, replaced pan gasket, filter, installed a Trans Go shift kit, replaced the modulator, front main seal.

    Could the kickdown cable somehow be causing my 3rd issue? Any tips on getting it installed? Any other thoughts on 3rd gear failing? The car shifts fine 1st-2nd. Runs about 4k rpm at 70. Trans is still out, likely installed tomorrow or next day. Then i will know if i have 3rd and see if i got the leak, the only thing i skipped(leak wise) is the pump seal.
  2. Donuts & Peelouts

    Donuts & Peelouts Life's 2 Short. Live like it.

    Some people say the lockdown cable dosent matter but when I had a th350 it made a difference when it was hooked up right
  3. jaye

    jaye Well-Known Member

    The kickdown is your passing gear, when you accelerate hard it shifts the gears to get the speed up then goes back to 3D. You can also manually shift when encountering an incline. I didn’t have mine hooked up. It sounds like maybe your clutches are worn causing slipping going into gear.
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Unless the kick down link is stuck fully engaged, it shouldn't cause your issue. Easy to tell, grab the cable at the gas pedal and pull it full travel, then release, it should pull back in.

    Next, I would check the vacuum modulator. Pull it out and point the vacuum connection down. If any ATF comes out it is toast. Check it with a vacuum pump, it should hold vacuum, if it doesn't, it's toast. Make sure you have a good manifold vacuum connection from the intake manifold to the modulator, no crimps, no leaks.

    Next, pull the governor out and check the weights and valves. Make sure they move freely with no sticking or binding.
  5. mattd3933

    mattd3933 Member

    We had the the governer out to replace the springs with shift kit springs, it seemed fine. the modulator was replaced and we checked the vacuum getting to the modulator before pulling the trans. im going down to start the trans install soon, may finish it before i have to go to work. I will know soon if i have 3rd again, i made sure everything was moving freely in the valve body while it was open. if theres still trouble i guess its time for a rebuild or find another trans.

    BRUCE ROE Well-Known Member

    I had an unmolested TH350 fail to shift into 3rd after 95,000 miles.
    At first I did not notice, with a 2.41:1 axle revs were not that high. The
    shop repaired it under 100,000 mile warrantee, but I put in a TH400
    switch pitch and sold the 350. Bruce Roe

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