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Thread: Torque Converter clutch won't stay locked up

  1. #1
    Craig
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    Default Torque Converter clutch won't stay locked up

    94 XLT with the 4ALD automatic with 185K, but completely rebuilt tranny
    about 10K ago. Lately strange things with torque converter lockup. It
    usually works normally, with lockup right at 45 mph, and in and out
    like it should depending on load. If I stay under 55 or so, it is fine
    all day. If I get on the highway and cruise at 70 or so, it unlocks
    after about four or five miles, and then won't lock again - period,
    even if at lower speeds (but over 45). After a long shutdown, it again
    worked fine. This happened daily, whether warmed up to normal or not,
    but refused to do it for the tranny shop fellows after they fought with
    it for a whole day. So I took it home and it's doing it again. Lately,
    sometimes it doesn't lock at all when starting out in the morning (cold
    Michigan winter), so it's become less predictable and more
    intermittent. I assumed it might be something electrical (bad
    connector, etc.) but now it seems to be something sticking in the
    clutch activation mechanics. Do you think an additive might help, and
    then a drain, filter, etc. thereafter might help? Or is there something
    specific I should be looking for? Thanks.

  2. #2
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    When operating properly, lockup occurs at 45 mph in 3rd or OD, whether
    right off the bat on a 10 below morning or fully warmed up on a warm
    day. Haven't checked MAF yet, but no codes on analyzer at shop (when
    they couldn't get it to not work properly). The rest "seems" ok, since
    it runs great otherwise. I was hoping there was somthing I might find
    since getting to the shop is a pain, since I teach ('cept today with a
    foot of new snow:-) Onward....mush!

  3. #3
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    No lights. Everything looks normal. Stopping vehicle and restarting
    engine will not cause TCC to operate properly once it unclutches at
    highway speeds. It usually will be ok after a longer "cooldown", but
    lately it doesn't always. Now it's starting to act up at "normal"
    speeds (ie., 50-55) - - but not always. Driving me crazy, too! Stay
    tuned.

  4. #4
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Good shot at it, dr bob. And I believe it. But she's running strong
    with new plugs, wires, etc., and the odd thing is that once it unlocks
    on the highway, it will not lock up again all day - on or off the
    highway - until it sits at least overnight. Then it's (usually) back to
    normal operation as I described earlier. That "normal" is a very firm
    shift pattern, and solid lockup at 47 mph.

    Now it's unlocking more often at lower, steady, speeds. I'm starting to
    suspect temperature sensors. So strange!

    I'm almost tempted to put in a switch to activate the selenoid when it
    unlocks and sticks me with higher revs on a highway trip. I think that
    can be done without overriding the brake cutout, etc. Ultimately, there
    are three ways for the selenoid to operate: computer, manual switch,
    pressure activated switch (requires some careful drilling and tapping).
    Trouble is, if I ever sell it, I have to give a training session:-)

    Before I get to far, I'm waiting for warm weather and see how it does.
    No fun trying to crawl around at 15 degrees in a blowing snow or wet
    garage floor.

    Hmmmmmm

  5. #5
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Come to think of it, John. Long ago, and before the tranny rebuild, my
    CEL would come on when running at high speed in the mountains or when
    towing. On-off-on-off all day and night on a long trip. Get back to
    flatlands or unhook the tow, and no more light problems. Same thing
    after a long deceleration. Only at higher speeds and/or with a tow.

    I'm not sure if this is related to my problem, exactly, but
    interesting.

    I think that there is some sensing problem - related to temperature
    "differentials". I didn't notice the problem before winter (tho it may
    not have been there before winter), and how and how long I warm the
    vehicle up seems to make a difference when, or if, the lack of lockup,
    or unlock occurs.

    Then again, it could be a bad electrical connector that is
    temperature/moisture critical. When the tranny guys plugged in their
    analyzer, they couldn't get the problem to occur. Hmmm. Maybe it's in
    that connector (I'll check tomorrow). Or a sticking selenoid that is
    sensitive to a cold case and warm fluid, etc. I'm just doing the usual
    "looking for an easy way out" before getting too deep into shop
    expenses with an old but nice vehicle.

    By the way, probably pretty easy to install a temperature sending unit
    in the tranny. Lots available on that elsewhere.

  6. #6
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Just a quick aside, John. I used to know a sailor named John Riggs who
    sailed the Great Lakes in Michigan. Not a chance, I bet, but worth
    asking....

  7. #7
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Oops. Meant recreational sailing and cruising on the Great Lakes around
    Michigan. I was US Army 67-70 and wish I had been on the Kennedy. Less
    mud:-)

  8. #8
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Hey dr bob. Try this on for size. As fussy as I am, and careful about
    service, I checked my radiator and found my coolant down almost one
    gallon. The plastic overflow tank had a stain that I took for the fluid
    level, but it was empty. How I let it go this long, I don't know.
    Anyway, I'm thinking that it's really possible that this was causing
    the tranny problems. There may be a temperature sensor that was getting
    either 1) no coolant to it, or 2) only steam to it. Could this possibly
    give mixed signals to the computer and cause the TCC problems? My temp
    guage operated properly in the normal range. I haven't had a chance to
    go out and test drive it, but will tomorrow and see if the problem
    cleared up. I will also try to find out where the coolant is going. I
    know it's not going into the transmission, and don't suspect the
    engine, either, but likely a slow leak radiator-wise. Whatever is is,
    it's realively slow.

  9. #9
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Got an answer this morning when I drove to work. Outside temp about 45
    degrees. TCC locked up right away at 47 mph. About 5 miles down the
    road it unlocked, and would not lock again. So here we
    are....square one.

  10. #10
    Craig
    Guest Craig's Avatar

    Default Torque Converter clutch won't stay locked up

    Looks like the dirty MAF sensor was the curprit. Lockup is fine now.
    Lost the spark knock/rattle, too. Oh yeah, loose radiator hose clamp
    was the problem with the coolant loss. Dribbled down to a crossmember
    and dispersed, so it never showed up on the garage floor. Whew. All set
    for another 190,000 miles....

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