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700 r4 lock up question? Please HELP!!!

Discussion in 'The Garage' started by wed68, Mar 18, 2005.

  1. wed68

    wed68 Registered Member

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    I have a rebuilt 700r4 in an 84 k5 Blazer, I just put a new 350 in and the torque convertor is not locking up, I know there are kits out there to lock up the convertor manually but I would like to know exactly what makes it lock up in an 84 in stock configuration. Then any recomendations would be greatly appreciated! I do not want to burn this tranny up!!!

    Bill
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Well the solenoid in the tranny will lock it up during driving when its powered , preset I believe . And then when driving and you make sudden throttle changes the vacuum switch next to your power brake booster unlocks it . And as a safety feature the brake switch turns it off at stop lights :k5: :k5:
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    There's a vacuum switch on the firewall so it locks up only while cruising, and the brake switch to unlock it when you step on the brake. I feel like I'm missing one more component of the lockup wiring harness, but can't recall what it is.

    Depending on tranny, there are switches inside for 3rd/4th gear, which I believe in an older setup like yours would also "lock out" lockup in whatever gears GM determined it didn't need to lock up in.

    Do you have an ALDL connector on the lower edge of your dash on the driver side? If so, that should allow you to force TCC lockup.
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    there are 3 things for the lockup to work, the temperature switch on the thermostat housing, the vacuum switch next to the brake booster and the brake switch on the pedal assembly must be closed. then as long as everything inside the tranny is right, it should lock up when its suppose to.
     
  5. wed68

    wed68 Registered Member

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    Big83, The original thermostat housing is not there anymore, and the vaccum switch either, I guess I need to hook up one of the lock up kits I see advertised!


    Thanks
     
  6. Jonny-K5

    Jonny-K5 1/2 ton status

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    you know it only locks up in OD right?
     

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