Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

lockup in 700r4 won't kick out

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by backlash, Nov 30, 2000.

  1. backlash

    backlash 1/2 ton status

    Joined:
    Oct 21, 2000
    Posts:
    519
    Likes Received:
    0
    Location:
    Northern, VA.
    lockup in 700r4 won\'t kick out

    This is pretty humbling...

    Nearly ordered a tranny from Bowtie Overdrives. Logistics ended up being a problem. While I was looking for someone to install it, fround a guy who said he could rebuild my tranny with stall converter and corvette servo that I liked. Hey ... he has a K-5 and Suburban... must not be a bad guy afterall.

    Well here's where it gets bad. Very strong tranny (I feel), but won't kick out of lock up going up grade unless you tap and hold down brake pedal. Soon as you let off, locks up and and engine acrts as if it's lugging. I seem to think it's the converter. The builder has tried various shift kits to correct it.

    Anybody got experience with this? Anyone got anybody they can ask?

    The builder truly wants to make me happy, but I'm getting fed up and he's getting frustrated. Even got nasty briefly this morning.

    Thanks (I know ... told you so)
     
  2. 65FL

    65FL Registered Member

    Joined:
    Apr 11, 2000
    Posts:
    31
    Likes Received:
    0
    Location:
    Castle Rock, CO
    Re: lockup in 700r4 won\'t kick out

    I am curious, what stall speed is your convertor? I am by no means an authority
    but I wonder if your TV cable is adjusted properly. I don't mean by the simple
    instructions you so often find in the Haynes and Chilton manuals. I mean by
    pulling the pan and watching the plunger as someone in the cab works the
    throttle.
     
  3. backlash

    backlash 1/2 ton status

    Joined:
    Oct 21, 2000
    Posts:
    519
    Likes Received:
    0
    Location:
    Northern, VA.
    Re: lockup in 700r4 won\'t kick out

    I'm not exactly sure. It is supposed to be 1800, but suspect not! It's been adjusted many times (I don't know if correctly), and I don't know how. What I do know is that when it is cold, it shifts fine ... as I drive it stops kicking out. Then when going up grade the engine begins to lug. If I attempt to accelerate pedal goes down and so does the speed, b/c tranny stays locked up. I don't want to trash my motor.

    Any thoughts?
     
  4. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Re: lockup in 700r4 won\'t kick out

    The TV cable doesn't control the lockup. The engine computer does. Any time the ECM senses that the signal from the Throttle Position Sensor has increased by 2% or greater, it sends a signal to the 700R4 to unlock the converter. The singal goes into the tranny via one of the wires in the 4-pin weatherpack connector. Sounds like either that wire is bad or disconnected or the builder left the wire to the internal solenoid disconnected inside the tranny pan.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  5. backlash

    backlash 1/2 ton status

    Joined:
    Oct 21, 2000
    Posts:
    519
    Likes Received:
    0
    Location:
    Northern, VA.
    Re: lockup in 700r4 won\'t kick out

    Thanks Harry,

    I guess that makes sense, but why does it work OK when it's cold and not when it warms up? Have really played with the throttle pressure adjustment(detent?), b/c of the corvette servo. Shifting too soft then too hard.
     
  6. 65FL

    65FL Registered Member

    Joined:
    Apr 11, 2000
    Posts:
    31
    Likes Received:
    0
    Location:
    Castle Rock, CO
    Re: lockup in 700r4 won\'t kick out

    Harry makes a good point. But it raises a question, I was under the assumption
    that the ECM which controls the lockup on the converter, does so by telling the
    tranny when to lock up. Thus if the wiring was bad, or disconnected the convertor
    would never lock up. By reading your statement Harry, your saying it is the other way
    around. I.e. assuming I over the stall speed, the torque convertor will lock up
    unless the ECM signals otherwise. Is that correct?

    TIA,
    65fl
     
  7. backlash

    backlash 1/2 ton status

    Joined:
    Oct 21, 2000
    Posts:
    519
    Likes Received:
    0
    Location:
    Northern, VA.
    Re: lockup in 700r4 won\'t kick out

    Another thought ... Is it possible ... at all, that there is something wrong with the converter? Can a bad converter cause a tranny not to shift out of lock up? Set too tight?

    Also ... when putting my foot in it, when shifting from 2nd to 3rd ... engine revs up (slipping) and check engine light comes on. Any ideas on this?

    The latest thing is the builder is now saying the engine is the problem. Says it may be missing. Of course, I put my foot on the brake and stepped on the gas ... no miss here, at idle or under load.

    Thanks again
     
  8. 6.2Blazer

    6.2Blazer 1/2 ton status

    Joined:
    Feb 24, 2000
    Posts:
    4,675
    Likes Received:
    26
    Location:
    Ohio
    Re: lockup in 700r4 won\'t kick out

    I'm not a tranny expert, but from what I have heard is that a faulty torqe converter normally will stay unlocked. However, since it seems to unlock properly when the brake is applied and then lock back up when the brake is released it would seem that the converter itself should be okay. This would then leave me to believe that there is something wrong, or a loose connection, somewhere between the ECM, throttle position, and tranny in regards to the amount of throttle required to unlock the converter.
     
  9. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Re: lockup in 700r4 won\'t kick out

    The ECM does tell the tranny when to lockup. I'd have to look at the wiring diagram to figure out exactly how it works. Off hand I'd say that there's probably 12 volts constantly applied to one side of the solenoid that applies the hydraulic pressue. Then the ECM just grounds the other side of the solenoid to engage it.

    However, I'm pretty sure that the internal hydraulics can also override the lockup feature and keep it turned off until everthing is ready, regardless of what the ECM says.

    The slipping going into higher gears is a bad thing. Something in that tranny is NOT put together correctly or the TV cable is grossly misadjusted. The TV cables are self adjusting, you should just have to set it once and forget it. Up at the throttle end, press the little D-shaped release button and pull the cable back towards the firewall. Then press the accellerator all the way to the floor. You'll hear a few ratchet-like clicks as the cable adjusts itself.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  10. backlash

    backlash 1/2 ton status

    Joined:
    Oct 21, 2000
    Posts:
    519
    Likes Received:
    0
    Location:
    Northern, VA.
    Re: lockup in 700r4 won\'t kick out

    I guess what I'll end up doing is going to Hatteras this weekend anyway. Either lightly keep foot on brake or down shift out of overdrive on the hills. As I work too much , will have to take it to the dealer after all. Afraid if I take it somewhere else, they'll say they have to pull it.

    Just frustrating, after all this time.
     

Share This Page