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Can anyone explain torque converter slippage, lockup/nonlockup: adv/disadv

Discussion in 'The Garage' started by mrk5, Jul 1, 2004.

  1. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    The TH400 does not have the lockup torque converter. So according to what I read if you are using gear-mph-rpm-tire dia formulas, you need to add about 300rpm for a TH400. (Which works out about perfect for the 3.08s I think I must have.)

    This seems like a bad thing.

    I primarily use the blazer to tow our camper up to the mountains and hit trails ranging from 1-7 difficulty.

    I'm wondering if a 700r4 would be better.

    I'm just wondering if there is an advantage to the slippage in the TH400.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Can anyone explain torque converter slippage, lockup/nonlockup: adv/dis

    Someone else can have fun explaining it, but imagine the torque converter clutch=TCC (what lockup trannies use) as a clutch on a manual transmission vehicle.

    Problem is, the TCC is not made for high loads...thats why the thing unlocks at certain times. Towing, you wouldn't want it locked, too much load on it.

    Of course the downside is slipping in the converter when not locked up, which generates heat.

    Lockup is good for low-load situations, for economy.
     
  3. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Re: Can anyone explain torque converter slippage, lockup/nonlockup: adv/dis

    Well towing a camper, you wouldn't want to use 4th gear anyway, you would want to use 3rd gear , which is same as the high gear in your th400 or 1 to 1 . Save time and money and leave your tranny in there. /forums/images/graemlins/k5.gif
     
  4. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    you need to add about 300rpm for a TH400. (Which works out about perfect for the 3.08s I think I must have.)



    [/ QUOTE ]My friend, nothing works out perfect with 3.08 gears unless you are running something like 29's or smaller. /forums/images/graemlins/smile.gif

    Lock up saves a lot of fuel and helps the tranny run cooler. I know that most th350's in the early 80's had a lock up converter but I don't know about th400's...would be nice to have it though.
     
  5. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Re: Can anyone explain torque converter slippage, lockup/nonlockup: adv/dis

    [ QUOTE ]
    Save time and money and leave your tranny in there. /forums/images/graemlins/k5.gif

    [/ QUOTE ]
    That's my goal!

    [ QUOTE ]
    My friend, nothing works out perfect with 3.08 gears unless you are running something like 29's or smaller.

    [/ QUOTE ]
    I meant the math. Trust me the 3.08s are by no means "perfect" /forums/images/graemlins/rolleyes.gif
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Can anyone explain torque converter slippage, lockup/nonlockup: adv/dis

    No Lockup TH400's.

    There were switch pitch ones in the 60's (angle of the blades in the converter changed based on throttle position IIRC) but thats about your only option in that tranny. Not until it was the 4L80E did you get lockup.
     
  7. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Re: Can anyone explain torque converter slippage, lockup/nonlockup: adv/dis

    Which leads me to conclude that since most of the travel we do is in the mountains, it wouldn't be locked up even if I did have a 700r4. So I might as well stick with the 400.

    It just seems ineffecient for it to slip.

    Good thing I installed an auxiliary cooler.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Can anyone explain torque converter slippage, lockup/nonlockup: adv/dis

    [ QUOTE ]
    It just seems ineffecient for it to slip.

    [/ QUOTE ]

    It IS, thats why manuals are better. /forums/images/graemlins/smile.gif

    Seriously though, thats one of the reasons for the slightly better economy through a manual...which is one of the driving reasons for the TCC to be used.
     

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