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Thread: Cold Start Slip

  1. #1
    Carthago delenda est Lutrova's Avatar
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    Default Cold Start Slip

    I know I had mentioned this issue before in my TC's main thread, but I thought it might be worth splitting into its own discussion.

    Back in May I ran into a transmission issue where the car seemingly wasn't fully in gear. Well, I ran into the same problem again today, only this time I wasn't parked one level underground.

    The symptoms:
    * Only occurs on cold start, but the car seems to engage into Reverse and Drive normally.
    * When moving forward, very little power is making it to the wheels. Enough to go forward on level ground, but just barely enough to make it up a one story ramp.
    * There's a whirring sound like a turbine spooling up coming from under the car. It follows pressure on the accelerator pedal but peaks shortly after letting up.
    * After shifting into Park and back the trans behaves normally, and the issue doesn't recur on subsequent (non-cold) starts.

    Between May and now I've replaced the trans filter and at least 8 quarts of fluid. I would think if this were an issue of worn out clutches, I would be slipping constantly and not just in one condition. But beyond that I'm not really sure where to look.

  2. #2
    Wagon Addicted Tiggie's Avatar
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    Default

    I'm no expert but I have a couple possibilities. I wonder if there is a hardened seal that's allowing the torque converter to partially drain. Check the fluid level before starting it - this will give you likely higher reading than normal but just reference it. Then drive the car until the problem stops. Let it sit a minute, car off and in park, and check the fluid again. Compare to the original cold reading. If the initial cold reading is significantly higher, the torque converter is draining back.

    My other possibility is there is a sticking valve or check ball, or some trash in the valve body.
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  3. #3
    Carthago delenda est Lutrova's Avatar
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    Default

    That makes sense, at least in my own totally ignorant opinion. The way it's only transferring partial power coupled with the turbine-like noise strikes me as a torque converter issue, specifically a lack of fluid. The fact that shifting in and out of park corrects it might suggest the problem lies in the valve body.

    This is an issue that's occurred three times in the last six months, though, so getting repeatability to help narrow things down might be tough.

  4. #4
    GMN Regular WagonMan's Avatar
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    My 90 CP does the same thing when it gets cold out. In colder months I start the car and let it warm up for a few minutes before driving it. DON'T make it slip by goosing the gas! You will kill whats left of the usable life of the transmission! WagonMan
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  5. #5
    GMN Regular DerekTheGreat's Avatar
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    I'd check the filter. Didn't Thain say if you overtorque the bolts or whatever holding it up in there you can have issues? It slipping when cold sounds like maybe the fluid is low or it's sucking air..
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  6. #6
    Carthago delenda est Lutrova's Avatar
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    I believe the filter can cause 3-4 shift problems because one of the bolts runs next to a valve or something that handles that shift. But I doubt the filter is the culprit here since this issue has occurred before and after replacing it, and my 3-4 shift is fine.

    As far as the usable life of the transmission goes, I understand that these things have limited lifespans. But a trans isn't an enigma that either works or it doesn't. Just like the engine, there are serviceable parts in it, with varying degrees of difficulty getting to and replacing them. And if I pull the engine and trans soon, I ought to have a decent chance of addressing whatever this slipping problem might be. Of course, if it's bands or clutch plates that's a bit of a job. But the valve body and torque converter are both pretty accessible, and it seems like one or both might be the culprit here.

  7. #7
    I'm an air-conditioned gypsy gadget73's Avatar
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    guessing you've got something sticky in the valve body causing either the forward clutch to not engage, or the 1st gear clutch to not apply.

    shop manual diag for "no or delayed forward engagement, reverse OK"
    improper fluid level
    linkage misadjusted / damaged
    low main control pressure (leakage)
    forward clutch stator support seal rings leaking (no 3, no 4)
    forward clutch assy burnt/damaged
    forward clutch cyl check ball leaking / leaking piston seal rings
    valve body bolts too loose/tight
    filter plugged
    pump damaged/leaking

    the only other symptom that kind-of applies is this one
    Slow initial engagement
    fluid level
    linkage
    contaminated fluid
    improper clutch and band application, or low main control pressure.

    might be worth having a gander at the shift linkage to be absolutely sure its going fully into gear. Everything else seems to either not apply, not be it since its already been checked, or not something thats fixable in a way that doesn't involve a teardown.

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