Torque convertor keeps unlocking
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5.0 and 5.7 Discussion, Torque convertor keeps unlocking in Cadillac Engine Technical Discussion; Lets try again,,,,89 FWB complete tune-up, tcc keeps unlocking around 60 but will do it randomly, replaced spedometer cable after ...
  1. #1
    54Cadillac is offline Cadillac Owners Member
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    Torque convertor keeps unlocking

    Lets try again,,,,89 FWB complete tune-up, tcc keeps unlocking around 60 but will do it randomly, replaced spedometer cable after 99dollar dealer failed diagnostics. The speedometer still bounces and maybe its the speed sensor? Where is the speed sensor and does it affect the signal to the TCC? I read somewhere that if the computer senses a speed change of given % the tcc signal would open. Since my speedometer cable is bouncing after replacing it and making noise at back of speedometer/// What are the wires leaving the back of speedometer by the speedometer cable? Help!

    brake pedal switch is new, I could see where the old contacts inside were bad and had buildup, but problem still there.

    I put multimeter on ALDL (A and F) driving down the road, reads 12volts plus, with brake pedal reads zero volts, when tcc signal goes out now, I noticed if i speed up it will lock back up or even if I remove gas pedal quickly that it will lock back up.

    Question? Is A and F tcc signal (12V)sent from computer to converter or is it the complete circuit including the tcc wiring in the trans?

    If speed sensor is problem? Where can I buy it?

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  3. #2
    Gwokable is offline Cadillac Owners Fanatic
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    Re: Torque convertor keeps unlocking

    You're thinking backwards but in the right direction .

    Trans sets the speedometer cable tension, not the other way around. Just make sure the cable is tight.

    The TCC solenoid has 4 seperate lines going into it: 2 Grounds, a 12V line going to the TCC solenoid, and a Diag line.

    Basically, the parts that can cause your problem are:

    Throttle Position Sensor is bad: ECM sets its TCC lockup advance based on how heavy the throttle is pulled. If the throttle sensor is bad, the ECM may lock up the converter while the car is coming to a stop or, alternativally, decide since the throttle is choked to remove lockup while the car is going.

    TV cable is improperly adjusted: Determines the governers shift advance; if it's too loose bad things happen.

    Fluid levels are too low or high: Self explanatory.

    Brake petal switch or wiring is bad: ECM unlocks the converter based on when you hit the brake petal. If any of those are bad, you'll have an issue.

  4. #3
    54Cadillac is offline Cadillac Owners Member
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    Re: Torque convertor keeps unlocking

    New brake switch, new tps, I adjusted TV cable in accordance with Haynes manual. Any tips on how to do that incase I messed it up? I basically pushed button on TV by carb and then opened throttle all the way and it seamed to self adjust???? This Caddy runs perfect except for this issue, new shocks going on monday. I hope I can fix it soon!!! thanks.

  5. #4
    54Cadillac is offline Cadillac Owners Member
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    Re: Torque convertor keeps unlocking

    one more post and i can pm someone!!!! yeahaaa!!!

  6. #5
    Gwokable is offline Cadillac Owners Fanatic
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    Re: Torque convertor keeps unlocking

    Well, I gave you a list dummy

    These are what can cause it:

    TCC solenoid
    TCC Solenoid wiring
    Torque Converter
    Brake switch
    Brake Switch wiring
    TPS
    TPS Wiring
    Throttle valve cable and assembly.
    Fluid Level
    Fluid condition

    What you have checked

    TCC solenoid
    TCC Solenoid wiring
    Torque Converter
    Brake switch

    Brake Switch wiring
    TPS
    TPS Wiring
    Throttle valve cable and assembly.

    Fluid Level
    Fluid condition

    Anything not highlighted should be checked. Get yourself a digital multimeter and have fun.

    Start with the fluid; if it smells burnt or isn't bright red, replace it. If it's brown then you have radiator fluid in the trans so get it rebuilt. As a note, the Dealer Service Manual for your car has all the info you could possibly want on rebuilding a trans.

    Also, adjusting the TV cable isn't too hard. So long as it has tension you should be OK. As I said before, what it does is adjust the speed atwhich fluid is allowed to be pumped into the governer; as the throttle opens, so does this valve and this allows the valve body (or governer, I forget which) to recieve fluid more quickly and shift more quickly. If the valve doesn't open then pressure builds up on the other end, more importantly, gears begin running outside of their stated RPM ranges and you fry the transmission in short order.

  7. #6
    54Cadillac is offline Cadillac Owners Member
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    Re: Torque convertor keeps unlocking

    Who's the dummy?

    The speed sensor behind the speedometer is bad. (Not on your list haha!) Cost over 250 to send it off. I put on a B&M TCC Lockup kit for $163 and new shocks the other day. No more problem with trans lockup!!! The dealer charge of 99 pushed me in the right direction after going back to him and telling him that it wasn't the speedometer cable, he told me, I had to get the bounce out of the speedometer needle or it will keep unlocking. Apparently if the speed sensor changes speed a given percent in a given time she will unlock TCC. It was cheaper to put in the kit like the streetrods use so they can have overdrive trans. in non computer cars. While it was on order I had a toggle switch between A and F on the ALDL. I only forgot to unlock the TCC one time!

    Thanks to everyone who replied! Great site. Should i put the B&M sticker on the caddy? lol

  8. #7
    Motorboat is offline Cadillac Owners Member
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    Re: Torque convertor keeps unlocking

    Glad you got it whipped.

  9. #8
    54Cadillac is offline Cadillac Owners Member
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    Re: Torque convertor keeps unlocking

    Olds 307, Averaged 22plus mpg on a recent trip from VA to NJ!!!! One half tank to get there. Same for the ride home with 500lbs of tools in the trunk....This is definitely a highway cruiser. I'm not a fan of engine restore but I was burning oil and for the trip I used a can and it didn't burn much at all if any. I'm monitoring the oil now. Someone must have not maintained it well in the past. With several quick oil changes I'm hoping to clean it up.

  10. #9
    Gwokable is offline Cadillac Owners Fanatic
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    Re: Torque convertor keeps unlocking

    Probably was the solenoid that did it. To my understanding, the speedometer cable is tensioned by a gear in the trans that moves based on how fast some part spins.

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