Transmission problems (C4)

Discussion in 'General Maverick/Comet' started by CACollo, Mar 16, 2002.

  1. CACollo

    CACollo Member

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    Just thought i'd ask for your input on this:

    I just got my engine running, so anything is possible. The transmission has been rebuilt, with new clutches/bands/washers, torque converter, etc.

    When i open 'er up a little bit more than usual from a stop, the transmission will go through first quickly (shifts at ~2500-3000rpms) and the shift into second is VERY soggy. The 2nd to 3rd shift is great. Adjusting the bands does not seem to make a difference.

    I have gone through my book and done the following:
    -Adjusted and re-adjusted the bands several times to the correct specs
    -Fluid level is fine, but i do have a small leak on one of the lines (could that cause it?)
    -Vacuum modulator is new

    The shift in to second is very weak and i can feel the transmission slipping but it gradually builds pressure and accelerates.


    My best guess is that i need a new intermediate piston? I replaced the low-reverse piston several years ago, and the intermediate may have gone with it....and i just didn't notice it because the i6 didn't make enough torque to make a difference. Any other ideas?

    Thanks!
     
  2. K. Merring

    K. Merring Regular

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    Is the vacuuum modulator hose hooked up, and did you make any valve body changes?
     
  3. CACollo

    CACollo Member

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    Thanks for the response!
    Yes the modulator is hooked up. It is new(er)...about a year old. I wasn't able to do a complete test of it, but it holds vacuum (no tears, no fluid in the lines).
    The valve body is stock, no modifications.

    By the way, this is a '69 transmission, for what it's worth.....
     
  4. mavman

    mavman Member

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    you might try adjusting the vacuum modulator. Remove the vacuum hose, and inside the nipple should be a tiny adjusting screw. Try turning it in a turn or two, and see what happens. If you turn it in too far, it probably wont shift into 3rd, and it will have a lack of engine braking in low. If adjusting it doesnt help, you might have to install a shift kit.....which can be done yourself very cheaply. I think Old Guy has done it for a few pennies, and the trans shifts pretty good, for a c4. All you have to do is install a cotter key and remove a ball and spring, and drill a hole (I think...dont remember for sure).
     
  5. Old Guy

    Old Guy Member

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    Just a thought on your problem, sounds like a pressure leak to the apply circut. This is sometimes caused by a leaking valve body or servo piston seal. If the rebuilder accidently boogered up one of the two seals when installing the piston into the cover, then it will leak. I would try looking at that first, the best bet is to get a pressure gauge and hose and remove the small pipe plug in the case in front of the shift linkage. Get a long enough hose so you can read it inside the car. After starting engine engage trans in 1, should read 90 to 110psi. Same thing in 2, nuetral should be about 65 to 85. This will tell a lot about the various problems inside. Assuming the clutch paks and pistons were all installed correctly and the bands adjusted etc. I think the first two items I mentioned are a good bet. There is also an accumilator spring in the valve body that softens the 1 to 2 shift pressure and could be another thing to look at. Removing that spring and small rubber plug above it, then installing a cotter key to hold the cutback valve, on the other end, from working will give you full pressure to the shift(may have to wear a nedk brace !!!!!) etc. Try the pressure test first then go from there. Good luck
     
    Miguel Arzola likes this.

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