"sucking" noise from tranny and shaking TC lock-up??

Discussion in 'GM Powertrain' started by mateospeed, Feb 9, 2010.

  1. mateospeed

    mateospeed Member

    I have searched and found no information pertaining to this issue on my '98 GMC yukon (5.7L, 4L60E tranny).

    I have 2 problems, both started after replacing my dizzy seal and cap.
    1) The transmission makes a strange "sucking" or "rubbing" noise at low trottle posn's or idle. Once you move more than 1/2" down the trottle pedal travel, the noise goes away. Cannot determine if it's truly throttle or actually engine speed related, because it's an automatic!
    2) I'm struggling to get my facts straight about the operation of an automatic. The tranny works wonderfully (especially for 150k miles), shifts nicely and smoothly through to 4th gear. Then, as you get to about 50mph, when I ASSume the torque converter attempts to lock up, the RPMs drop to 1300 or so, you feel a little "bump", and the RPMs come back up to where they were before. If you're moving a little quicker, and you play with the trottle just right (not very much throttle), you can get it to actually lock in for a bit, and the truck with shake violently! When you release the throttle, the RPMs will come back up, and it will stop shaking.

    Additional info: i recenly dropped the tranny and replaced the Rear Main seal on the engine. When I re-installed, I did not completely fill up the Torque Converter. I did drain it when I took it out, but it was obvious that not all the fluid came out. I have 2-3k miles on the truck since then. Also, the fluid level is a little high, and is still nice and clearish-red.

    Last weekend, it actually ran well one day, randomly. No issues doing what I'm assuming was the TC lockup. Then it started again the next day. ??

    Any ideas? perhaps I burned up my TC by not completely re-filling it, and thus burned up the lock-up clutch?

    Checked so far:
    -vacuum leaks: found none. The sound is actually louder in the cab than in the engine bay!
    -no CEL's, none pending.
    -correct spark timing: would throw a code otherwise; engine runs well. I'm obviously suspicious of the work I just did, but it apparently is working fine. Coincidence??

    Thanks in advance!
    -Matt
     
  2. Gmcsuvguy

    Gmcsuvguy Rockstar 100 Posts

    Ok, shooting in the dark here...vacuum "sucking" noise is louder in the cab...are you having any issues with your heater operation? Possible vacuum leak inside the cab? TCC shudder when locked up is correct, you wouldn't have damaged it unless it was almost empty but fluid would have been brownish and smelt burnt. Could be a weak TCC solenoid or weak torque converter, most likely the latter. Hope this helps alittle.:glasses:
     
  3. mateospeed

    mateospeed Member

    Thanks for the suggestion!
    I'll check for vacuum leaks in the heater assembly, but the only vacuum line I found went to the heater valve, which is inside the engine bay. It wasn't leaking. I'll check again.
    Also, I'm assuming 'TCC' means Torque Converter Control?
    Thanks,
    -Matt
     
  4. Joeairforce

    Joeairforce Epic Member 5+ Years 100 Posts

    Torque Converter Clutch :glasses:
     
  5. mateospeed

    mateospeed Member


    Ahh, thanks.
     

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