Torque Converter lock-up

Discussion in 'VW Mk4 Jetta, Golf, New Beetle, Passat TDI forum' started by Kelso, Apr 21, 2012.

  1. Kelso

    Kelso New Member

    Joined:
    Oct 21, 2011
    Messages:
    19
    Car:
    2004 Jetta TDI Wagon
    Hello,
    I have a question about the transmission in our automatic 2004 Jetta wagon. I never really thought about it until recently, but I've noticed that the torque converter doesn't seem to lock up when we're driving on the highway. I have VCDS and have done a few scans when we got the car (I had to do a fair bit of catch-up maintanence) and I can't remember the code but I know I had a fault for a bad tranny temp sensor. It wasn't high on the priority list, and eventually I forgot all about it.

    I assume that the torque converter should lock up, at least in 5th gear, but I'm curious as to the possible cause of the fault. Could it have anything to do with the tranny temp sensor? I didn't have any other transmission related codes. I don't know if the tranny fluid has ever been changed before so at 260 000kms it could be quite overdue, could that be the cause of the problem? It does take a moment to shift between drive and reverse gears, but nothing too drastic, and it up and down shifts smoothly.

    Thanks for any insight and advice.
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  2. Keithuk

    Keithuk Super Moderator

    Joined:
    Aug 29, 2010
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    Car:
    2010 Golf GTD (170) CBBB
    Location:
    Stoke on Trent, England
  3. shuswap

    shuswap Member

    Joined:
    Dec 12, 2010
    Messages:
    183
    Car:
    2005 Golf TDI auto
    What rpm do you see at 100kph? Or....at some other convenient speed. I think I observed 1600 rpm at 80kph today. I'll verify that number if you want.
  4. Kelso

    Kelso New Member

    Joined:
    Oct 21, 2011
    Messages:
    19
    Car:
    2004 Jetta TDI Wagon
    I haven't scanned it recently, and I can't recall the exact cruising RPM. It's my wife's car so I don't drive it often, and I've been very busy with changing over my work truck and my civic engine rebuild (soon to have 3 turbo'd vehicles!)

    I suspect that it's not locking up because it's at a certain rpm under acceleration but drops down maybe 500 rpm when coasting. And I'm talking about light throttle here, I'm not confusing this with downshifting!
    I'll see if I can get a scan done before she leaves for work today.
  5. Kelso

    Kelso New Member

    Joined:
    Oct 21, 2011
    Messages:
    19
    Car:
    2004 Jetta TDI Wagon
    So, I can't find my VCDS...

    Anyways I have some more info about the issue. I've noticed that while I'm driving at 110km/h (70mph) it's at apx 2200 rpm and if I let off the throttle completely it drops to about 2000 rpm before the car starts to slow down, which doesn't seem like much of an issue.
    However, if I'm driving at 100km/h the engine is at 2000 rpm and if I let off the throttle completely it drops down to 1500-1600 rpm and when I press the throttle again it spikes up above 2100 rpm and then comes back down to 2000.

    It seems to want to do the same thing at higher speeds but not as bad, the issue is more obvious at about 100km/h and less.

    I have a Tundra and a Superduty with automatic transmissions and when they lock up, they are locked solid (unless you give enough throttle that the torque converter unlocks or it downshifts), but I don't think it's right that the tach should drop when the throttle is released.

    I'm probably going to have the tranny fluid changed in a few weeks when I'm back home again and I'll ask about changing the tranny temp sensor. Any other thoughts or recommendations?

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