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How do I tell if my 700r4 has a lockup TC?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Nov 8, 2001.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I know how a lockup TC feels........my 84 K5 has one and works great. The reason I'm asking is because my 83 6.2 1/2 ton(w/ a 700r4) doesn't. I had my injector pump changed out this spring, and the shop decided to adjust the way my tranny shifted. I was a little upset because the way they adjusted it made the truck shift like shite(in my opinion), so they put it back the way it was and I drove away happily.

    Now I'm a little concerned- it shifts fine all the way through the gears, but the only time I can feel the TC lockup is between 2nd and D(it's always done this so I assume it's a diesel thing). I honestly can't remember if it locked up in D before, but now it doesn't for sure.

    Soooooooooooo........how can I tell if my 700r4 ever did lockup in D? Is there a chance that the diesel shop screwed something up when they adjusted my shifts?



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  2. pcorssmit

    pcorssmit 1/2 ton status

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    All (factory) 700s have lockup converters.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  3. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    When you are flying down the road lightly put yer foot on the brake and press SLIGHTLY. You should feel it unlock. If you don't....push a bit harder...and if it still don't someone messed up the tranny.


    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
    If it wasn't for bad luck I would have no luck at all!!
     
  4. Blue85

    Blue85 Troll Premium Member

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    These guys are correct. Make sure that the lock-up is working or that diesel will fry that 83 tranny in a hurry. If you decide that it is not locking up, post again and we can walk you through the troubleshooting.

    <font color=green>There's nothing like the smell of a rich V-8 in the morning...</font color=green>
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I got ahold of my tranny guy and he provided 2 scenarios:

    1. The torque convertor IS locking up but it's so subtle that I can't feel it.

    2. The TC solenoid is shot and needs to be replaced.

    Either way, I'm going to let him check it out. I'll let you know what the outcome is when I figure it out.



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  6. pcorssmit

    pcorssmit 1/2 ton status

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    Could be a wiring problem, too.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    How could it be a wiring problem, Pete? I was under the impression that the older 700r4s aren't controlled electronically.......

    I don't know much about the internal working of trannies, so I hope I don't sound like a big dummy[​IMG]!!!



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  8. Triaged

    Triaged 1/2 ton status

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    The only electronic thing on them is the tc lockup.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Or just the vacuum line isn't hooked to the switch or the plug is not plugged in. :)

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  10. pcorssmit

    pcorssmit 1/2 ton status

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    Tim, which switch? I haven't looked at mine for some time, but as I recall the wire (hot with key on) ran through a switch on the brake pedal, and then down to the tranny.

    My truck was originally diesel, do the gas ones have a vacuum/electrical switch in there somewhere? Just curious, never really looked at one close, figured they were the same.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Vac/Electric switch is one of the two on the firewall, one is bolted near the Master Cylinder, facing the passenger fender, the other is on the passenger side firewall, near the top drivers side of the AC box. One is ESC and one is TCC IIRC, not sure which. Gas only I'd guess, although if the diesels ran vacuum pumps, and the vacuum depended on engine RPM, not sure why diesels couldn't have used a vac switch as well. HTH

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     

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