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torque converter lock-up problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 88blazer, Nov 30, 2000.

  1. 88blazer

    88blazer Registered Member

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    The torque converter in my ’88 700R-4 will not lock up properly. Occasionally it will work, sometimes it locks and unlocks repeatedly, but most of the time it doesn’t work at all. I figure that it is ECM related and is going to cost a bit of $$ to get fixed.
    Since my pockets are empty, I was thinking about unplugging the factory wiring and installing the TCI wiring kit for $72.

    This is off TCI’s site:
    Universal Lock-up Wiring Kit for TH-700R4 & TH-2004R - Installation of this kit makes retrofits into non-ECM TH-700R4 or TH-2004R vehicles a snap. System allows automatic operation of the TCC in 4th gear under stable engine operation, and disengages the clutch when accelerating or down shifting. Also provided in the kit is a manual override option. Constructed from OEM connectors and oil resistant wire, we install this kit in all our complete TH-700R4 & TH-2004R Street Fighter Transmissions. Part No. 376600

    I like the idea of the manual override and I can swing $72. Is this a good or bad idea?


    http://bernie.4t.com
     
  2. JimmyDie6.2

    JimmyDie6.2 1/2 ton status

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    I don't know the answer to your questions, but I had the same problem with my converter locking and unlocking over and over again. I was told to check the plug in the tranny for the lockup. I did, it somehow popped out. I put it back in and, wala it was working again, check the plug. Its on the drivers side, on the tranny, right above where the pan bolts on...........js
     
  3. Blazer1970

    Blazer1970 1/2 ton status

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    My '88 pickup started to do exactly the same thing you describe, so I traded it in for a new truck. Actually, before I did that, I did a little research on the TCC operation. Try replacing the coolant temp sensor (CTS). The computer will not let the converter lock when the engine is cold, so a flaky CTS could cause your problem. A flaky TPS (throttle pos. sensor) could do the same thing, but it seems like you would notice other driveability problems, or at least trip a fault code (my truck did not). Otherwise, before you spring for a conversion, I would haywire a switch to the TCC to make sure that the problem is not in the tranny or the clutch (bad TCC solenoid valve in the tranny?).

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  4. 88blazer

    88blazer Registered Member

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    I guess I should include a little more info.

    It isn't temp. related. Sometimes it works cold, then others times it will not work for 50 miles then work for a while. It seems totally ramdom.
    The truck runs fine, no error codes so I don't think it's the TPS (I could be wrong, this is my first FI vehicle). The MPG dropped a little, but I attribute that to the TC slipping all the time.

    I pulled the plug on the transmission. I tried to clean it, but my elbow doesn't bend that way so I just plugged it back in and no change.

    How do I hotwire the TCC?

    I tired the Hayes manual, but it's worthless. It mentions the VSS. Is there a way to figure out if it is bad?

    I miss my carb. and 5-speed.



    http://bernie.4t.com
     
  5. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Make sure to keep an eye on the condition of the tranny fluid. An improperly functioning TC can cause excessive heat build-up in the transmission which can fry it in short time. Burnt and blackened fluid can be a sign of excessive heating. This info came from a local tranny shop who said that a lot of the 700r4 failures they see were caused by a faulty converter.
     

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