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700r4 still screwed up! Lock up problem '88 k-5

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by backlash, Dec 8, 2000.

  1. backlash

    backlash 1/2 ton status

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    700r4 still screwed up! Lock up problem \'88 k-5

    I don't know what is right anymore. I had my tranny rebuilt over a month ago ... have taken it back 6 times now. The builder tried several times to fix the lock up, but now he says it needs a tune up and wires. The damn engine has 180,000 miles on it, but is still strong.

    How is this thing supposed to work?

    Since new, it would go into lock up in OD. When pressing on the gas I could feel it kick out and my truck would move on down the road. Now when driving up to 55mph shifts into OD and then immediately into lock up and stays there. When I try to accelerate it does nothing ... unless I push it to the floor. Then it drops back to third gear, engine races, goes faster, shifts into OD and immediately locks up. The only way to smoothly accelerate is to hold foot lightly on the brake, which will disengage the lock up. Wonder what the people behind me are thinking ... brakes coming on, but he's accelerating.

    The builder said he drilled the plate (I guess valve body ) to protect the warrantee. Too much? Any ideas? My thought is it was drilled too much and therfore, will not go in and out of lock up the way it was designed to do. Of course, this will protect the warranty ... no chance of burning anything up if it ain't working. Too much load on the engine.

    Please tell me how the transmission is supposed to work. I guess it's possible mine was wrong from the beginning, but liked it and it lasted 180,000 miles.

    Sorry so long, just so frustrated at this point.

    Thanks
     
  2. Blue85

    Blue85 Troll Premium Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    With an 88, the lock-up is supposed to be controlled by the ECM. There are usually 3 wires going to the transmission:
    1) 12V power - this allows the tranny to lock the converter whenever it is in O.D. This is done via a pressure switch inside the tranny.
    2) Lock control - This line locks the tranny in all gears but 1st when 12V is applied to it. The ECM should have control of this wire
    3) Feedback - this line is switched to ground whenever the converter is locked.

    The lockup inside the transmission is done with an electric solenoid, which controls the flow of fluid to the "lock-up part" of the torque converter. The fact that it does lock sometimes means that you have power going to the tranny. (pin 1 above) The fact that it unlocks when you touch the brakes implies that pin 2 is being used. Therefore, it seems that the problem is inside the transmission. You should ask the builder exactly what it is that he drilled. It kind of sounds like the lock up has been converted to manual by placing a check-ball above the solenoid, but then your brakes shouldn't have any effect. Are you sure that the this is the same transmission that came out of the vehicle? Many shops give you an already re-built equivalent so that your down-time is less. If you are not sure, a portion of the vehicle VIN appears on the tranny. If the transmission is from another year, it may not have the right internal wiring to work in your truck.

    Did the L/U work in 2nd and 3rd before the rebuild?

    "If it aint broke...Make it work better!"
     
  3. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Thanks Blue,

    I believe it did lock up in 3rd ... not sure about second.

    I guess I need to crawl under there and check that number. The reason I went there to begin with is b/c I wanted my tranny rebuilt vs. a rebuild from the dealer or elsewhere. I would really be pissed if this guy switched on me.

    What's the best place to cross reference the number. May still have the original paperwork from when it was new also.
     
  4. Blue85

    Blue85 Troll Premium Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    The number is on the passenger's side, just above the oil pan. You won't have to cross-reference it, it is a portion of the VIN. BTW, the numbers I used above don't really represent the pin-out for the tranny connector.

    Isn't this guy backing up his work? The converter lockup is part of the normal functionality of the transmission, so if it isn't working right, it is his problem.

    "If it aint broke...Make it work better!"
     
  5. HarryH3

    HarryH3 1 ton status Author

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Your tranny builder is full of $h!t. A 700R4 has NO vacuum reference, so it doesn't care how well the engine is running. A tune up of the engine won't have any effect on how the tranny or torque converter operate.

    According the GM factory service manual, the ECM will send the "unlock converter" command to the tranny any time that the TPS signal increases by 2% or more. You should not have to floor it to get the converter to unlock.

    The only other input that the tranny has is from the TV cable, which adjusts internal hydraulic pressure in the trans, based on throttle postion. It's the cable that attaches to throttle, just next to the accellerator cable.

    There is something wrong with that tranny, not with the engine. [​IMG]

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

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Read you posts a while back and I keep telling him this. I've contactd VISA to protest this payment. I'm over it. Too much energy and time to continue with this crap.

    Thanks for everything.
     
  7. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    He says he knows what I'm talking about, keeps saying he fixed it. Possible he doesn't let it get hot ... only happens when it's warm and really noticeable on the interstate and, more so, going up grade. Just have been giving him the benefit of the doubt for too damn long.

    Guess I have to get nasty. Really like this guy, but enough is enough
     
  8. Blue85

    Blue85 Troll Premium Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    So before it gets warm the lockup works normally?

    "If it aint broke...Make it work better!"
     
  9. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Yes it does. After about 20 minutes of driving it starts messing up.

    Here's the latest ... phone Co. cut phone wire outside my place no internet access till Sunday AM.

    But, I sent the builder a long note, stating my beef as well as a copy of the responses you guys gave me. He called back and insists that I tune it up, that since it's such an old motor that is what it needs it. I've always replaced things under the hood with OEM parts so I think he's under the impression everythings original. Well it does need a tune up, kinda pissed that I have to pay someone to do it since my tools are an hour and a half away. But this guy also said if that doesn't correct the problem he'd give me my money back in cash. Still trying to make me happy. I do not believe it will work, but that is what I will do.

    Please respond if you have other ideas ... will check the site as soon as I get access, hopefully Sunday AM.

    How would acting up if warm make a difference?
     
  10. jarheadk5

    jarheadk5 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Leaving the engine and the rest of the drivetrain completely out of this:

    Assuming the fluid level is correct, not over or under;

    If the transmission works correctly when it is cold, but stops working correctly when it gets up to operating temp (warm, hot, whatever), then it is a TRANSMISSION problem, just as you and the rest of the responders have concluded.
    I don't understand why your mech can't seem to grasp this very simple concept.

    [​IMG] Semper Maintenance!
     
  11. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Ken,

    I detect my frustration has slid your way. That cracked me up! I think this guy feels that my truck won't accelerate up hill due to lack of power. Obviously, it has plenty if I can tap on the brake pedal and she goes like a bat out hell! That is once the lock up is disengauged.

    I will show him your post as well.

    Thanks
     
  12. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Ideas....

    Torque Converter Clutch Solenoid...tells when the sucker is to lock up..its under the pan, remove it put a new one back..$30.....

    TV Cable...tells what position the skinny pedal is in and if to "kick down" and give more go go in the tranny....located around the throttle cable...don't know how to adjust it..

    SK-15
    J**P...it's whats for dinner!
    http://SK-15.coloradok5.com
     
  13. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Thanks SK-15,

    All makes sense, just figure this guy should fix it ... since I paid him to do that!

    Same story, different day. Called a parts store for wires ... $9.00 cheaper than the dealer. Went in Sunday ... said they'd have to order and it would cost $5.00 more and I'd have to wait. Needless to say, dealer closed and I chose not to get screwed again. No tune up yesterday. Thank God for public transportation.
     
  14. jarheadk5

    jarheadk5 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    I deal with attitudes like that at work A LOT!! We'll have a problem with something on the aircraft, one shop (AVIONICS!!) will come out, take a quick peek, and say "It's not electrical, it's _______" and leave. Hours later, after the other shops do the proper brainstorming and troubleshooting, we find that is WAS electrical to begin with. WASTED man-hours that we could have gotten something else done in. Just drives me batty...

    [​IMG] Semper Maintenance!
     
  15. Beast

    Beast Registered Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    I went through this with a 88 S-10 years ago and found the following.
    If you have a TBI (Throtle Body Injection) instead of a carb, there is a throtle position sensor that sends a signal to the ECM to disengage the lockup converter under acceleration. With electonics it is conceivable that the sensor could be functioning normally when cold but failing when hot. The sensor is a very little unit about 1" ~square on the base of the TBI unit. This is about a $15 part from Kragen / PepBoys and can be changed in about 10 minutes with simple tools. Since the other inputs to the trany (ie the full throtle kick down and the brake seem to cause the trany to function corectly it is my guess that it is the position sensor. I hope this helps, good luck.
     
  16. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Hey Beast,

    Will definitely check that out! Please tell me what side of the TBI I would find it. At work and guess it'll be easy to locate, but will make it easier to find, while tuning up next weekend. Thanks.

    Would be awesome if this would fix the problem. Kinda like spending $3500.00 over ten years to fix a wandering front end and a $110.00 steering brace finally taking care of it!
     
  17. Beast

    Beast Registered Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    As I remember, it was on the right hand side of the TBI (as your sitting in the truck).
     
  18. backlash

    backlash 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Thanks Beast,

    Inflation ... $36.99 these days. Will do the tune ... give it back to the tranny builder, get my money back (if he remembers saying that!) and start to diagnose per you guys.
     
  19. ftn96

    ftn96 1/2 ton status

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Just from my knowledge of computers and the basics of electronics, I would guess the position scensor may be the cause. Cause electronics are very funny with heat. And since your having problems when it gets warm. Go for it. Spend another $3500. Least you'll know what all is good and whats bad. LOL!!! My wife said that to me last night. But not the $3500 part.

    I miss my Ex, but my aim is getting better!
    http://mccordhouse.freeservers.com
     
  20. Beast

    Beast Registered Member

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    Re: 700r4 still screwed up! Lock up problem \'88 k-5

    Did you ever get the problem fixed?
     

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