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700r4 and lock up problems revisited

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by backlash, Apr 11, 2001.

  1. backlash

    backlash 1/2 ton status

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    Hey Guys,

    Weather's getting nice again and I'm going to give this one more try.

    I smoked my tranny, took it in for rebuild, afterwards the tranny went from 2nd to 3rd with the clutch locked, then would shift to OD locked. Clutch will not disengage with cruise on, when accelerating ( therefore, cannot go up hills without engine lugging). After taking it back I have a tranny that won't kick out of lock up when warm ... WORKS FINE WHEN COLD!

    I got money back less some other work done( tune up) and taking time off to hold the builders hand for a 2 hour road test. At the end of which he said nothing is wrong.

    Anyway, I can manually downshift to 3rd when climbing hills or tap and hold brake (which will unlock the clutch) to accelerate.

    QUESTION: Will this manual switch that BOWTIE sells aftermarket, to unlock then lock up converter work like the manual type application of a brake pedal. Just looking for an inexpensive way to unlike the OD locked clutch when cuising down the interstate without slowing down, holding brake pedal or lugging the motor.

    The builder said he drilled the plate (valve body?), put in a shift kit, and put in a convette servo with a stall converter. (the last two he eventually removed and replaced with stock applications)

    Any ideas?

    Sorry for you guys that have suffered through this with me!
     
  2. 89Blazin

    89Blazin 1/2 ton status

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    The term "clutch".....are you talking about the torque converter? Engaging and disengaging the torque converter? If so.....I am seeing the same thing (I think) with my 89.....350tbi / 700r setup. I loose alot of speed going uphill, while in OD and the cruise engaged. It seems to me my TC is not unlocking. Is this the symptom you are describing?

    85 Burb and an 89 Blazer
    One just for fun, one simply for pleazer
     
  3. backlash

    backlash 1/2 ton status

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    Exactly! Mine works fine when cold ... then after about 20 minutes the lock up converter (clutch) stops disengauging when trying to accelerate or go up hill (under load). If I touch the brake lightly, the clutch will disengage and allow the engine to speed up therefore allowing me to climb hills or accelerate.

    Accourding to the manual it could be the brake switch or (I think, don't remember) power piston in the pump, but I'm through with it ... tried to save some money off the dealer stock tranny and I messed up! I think the builder put in the wrong shifter ... who knows? Plan to drive it into the dirt! The go back to stock ... the original lasted 180,000 miles.

    Anyway, anyone know how to bypass this without wearing out the brakes or engine?

    89 blazin,

    See if touching and holding the brake while under load in OD kicks out the clutch. If so you have the same problem. Is it a new tranny? A new problem or is the truck new to you? Does work OK when cold?

    Thanks
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    The ALDL connector in the cab *should* have two pins you can "jumper" to lock the converter. On the cars its the A and F pins, which are upper left and upper right..not suggesting you do this without finding which two pins are the correct ones though..paper clip works fine. You could always wire a toggle in that way, but I think thats hokey. Fix it the right way, which I think you probably do, but don't know where to start. Are you sure the vacuum sensor in the engine compartment is hooked up? Should be bolted/screwed onto the brake booster baracket..one vacuum line, one wire. You could pull the brake/cruise switch off the bracket and play around with it while driving...pushing it in at speed should lock the converter.

    So not unlocking sounds like it could be vacuum switch related, although not real likely, since no vacuum(switch disconnected) should=unlock.

    Working when cold, then not when hot is TYPICALLY a problem with the TCC solenoid. BUT they also will typically kill the motor after getting off the freeway, since it won't ever unlock.

    The TCC circuit is pretty simple actually, look at the plug on the tranny, it's only 3 wires.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  5. Blue85b

    Blue85b Registered Member

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    Backlash:
    what year is your rig?

    If it is TBI, the L/U is controlled by the ECM. Since the brake switch works to unlock the TCC, we know that the solenoid is good. Therefore, the problem is probably outside the tranny.

    On 86 and earlier rigs, there is a ton that I could tell you since I have chasing some L/U problems myself (currently it only locks in 2nd and 3rd...). If that is what your truck is, I would suspect that you have a sticking lock-up control valve. However, if that is the problem, it is strange that you get lock-up when it is cold. Are you sure that the clutch is not always open when it is cold?

    After rereading your post, it almost sounds like the transmission is not automatically shifting from 4th to 3rd? If so, the whole problem may be the TV cable, the TV valve or one of a few other valves that may be sticking. That means that you always have the hydraulic signal to lockup, but it doesn't lock at all when the engine is cold until it gets the electrical signal to lockup (solenoid) and then it is always locked until you hit the brakes. This makes sense since you need both an electrical AND a hydraulic signal to lock the converter (except on TBI models).

    Answer my questions and I can help you more.
     
  6. 89Blazin

    89Blazin 1/2 ton status

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    The truck is new to me. Others (Bondo I remember) of us have been in the same discussion on 2 different posts.....several of us have the same problem.

    Truck has 20,000 miles on engine/tranny. Pleased with everything except this minor nusance.

    85 Burb and an 89 Blazer
    One just for fun, one simply for pleazer
     
  7. backlash

    backlash 1/2 ton status

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    Was it like that when you got it?

    May be the reason the guy got rid of it! Entertaining the thought myself!
     
  8. 89Blazin

    89Blazin 1/2 ton status

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    Several of us have the same problem....seems to be all with 89-91, 350 TBI, R700. Trannys are all working great. Example....70 MPH with cruise on, come to a slight incline, I will lose 15 MPH before the tranny downshifts on it's own. Seems like the TC is staying locked. I come to a steep hill, I get an immediate downshift and the speed doesn't bleed off. The cruise is pulling my acc. pedal in slowly, but no downshift until I lose all that speed. Steep hill...my cruise doesn't even move the acc. pedal before the downshift takes place. I can tap my acc. pedal going up the slight incline, and get the downshift. My problem is not heat sensitive, it's that way all the time. Kinda the opposite of a normal R700....instead of back and forth D to O to D....mine never wants to drop down into Drive. It stays in O until I'm down to around 1100 RPM up the incline before it downshifts.

    85 Burb and an 89 Blazer
    One just for fun, one simply for pleazer
     
  9. CaptCrunch

    CaptCrunch 1/2 ton status

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    Blue-The tranny shouldn't be locking up in second... if it is is FUBR.
    It seems like another problem w/ rebuilt 700's hmmm... I'm confused about what was done to the trans... if it has a higer stall converter in it that's going to effect operation some... also if the dingleberry didn't put a new converter in or flush out the system there could be crap all over. Probably first thing is get the kickdown or tv cable adjusted... this will cause a lot of similar problems. If the converter unlocks when you tap the brake then that works... the next step from there would be to look into the TCC (which is very likely) and probably check the pressure in the tranny... which will check pressure regulator, pump, TV valve, etc. If things still don't clear up it is probably time to pull out the valve body and find out WTF this guy did... are the check balls in the right spots... where did he drill and where did he fill.. etc. Hopefully it is nothing major. Good luck!

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  10. backlash

    backlash 1/2 ton status

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    More history ...

    Truck was working fine ... took it to Hatteras, wheeled on the beach without removing any air (dumbass, I know better!) Obviously, got it too hot! Slipped once two days later while still there. Upon driving home ... punched it and it just smoked 3rd and OD. I guess I got it too hot.

    Importort possibility... but not likely ... the ECM went out at the same time...

    Two moths later I had the tranny rebuilt ... as mentioned in earlier post.

    At first, it tried to lock up in 3rd as well as OD. The builder rewired something down by the tranny (?TCC) so that the lock up would not engage in third. It definitely works correctly in OD when cold, can feel it shift to OD then lock(engine RPM's drop), and out of lock up when accelerating or going up a hill. When warm, it shifts from 3rd to OD lock up instantly(engine RPM"S again drop). It used to kick out almost instantaneously, but now there is a delay! Have tuned it up as well as replaced brake M/C and booster, but had no change in symtoms.

    &lt;&lt;Are you sure the vacuum sensor in the engine compartment is hooked up? &gt;&gt;

    No, but if that's it I'll just die! You mentioned I'd like to avoid the hokey fix. I've been working on this for months .... would love to get it right!

    &lt;&lt;The ALDL connector in the cab *should* have two pins you can "jumper" to lock the converter&gt;&gt;

    Don't want to lock ... is there a way to jump to unlock?

    Also ... this may have something to do with speed. At interstate speed ... will work fine when cold, then when slowing down at a major interchange to stop or as slow as 35 mph, then accelerating at any rate to &gt;55mph it will skip OD and go straight to OD locked.

    This happens every time! Sometimes I can drive nearly a half hour at highway speed before it acts up.

    Thanks
     
  11. backlash

    backlash 1/2 ton status

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    Hey Cap,

    I think this guy screwed up the rebuild! He pulled the tranny again and removed the servo and new converter and put in a stock application converter.

    You metioned all the test ... checking pressures lookinfg at the valve body, etc. I have the equivalent of $600 into this with tune up ... long story and missing work.

    What would it cost to have this checked and where do I go. Sounds to me that I'll be up to where the dealer wanted for a rebuild with a 36/ 36,000 mi. warrantee. Right now I have a tranny the works although not correctly.

    I guess that's why I want to drive it into the dirt.

    Any idea how to electrically unlock the clutch type torque conterter with a toggle? So I can use it to get over the hills on the interstate?
     
  12. backlash

    backlash 1/2 ton status

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    1988

    Sorry was answering the e-mail I read so I confused your post with another.

    Please see my post this day at 11:32 to dyeager (thought I was responding to only one not both) so I don't need to repeat it for all to read!

    Thanks,

    Back
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, with ALDL jumper, you can run the TCC seperate of the Vacuum and VSS...thats what I was referring to as "hokey"

    I really don't think it would be the vacuum switch, simply because the switch would read no vacuum as time to unlock..without it hooked up, you should never lock up I would imagine. I know that is a part of lockup though, and eery easy to see if it is hooked up.

    I'm guessing that 3rd gear lockup is handled by a pressure switch, and he just disconnected the wire for the switch...

    I'm trying to get around TPS and CCC to run lockup as the factory intended in my car, and it is the same basic system...but relatively hard to get to work as the factory intended it to...it needs to be completely automatic, and work correctly! : )




    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  14. Blue85b

    Blue85b Registered Member

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    For an electrical "band-aid" to let you unlock the converter with a switch, you just put the toggle in series with the brake switch. I know that on mine the TCC brake switch is seperate from the main brake switch, so that would be no problem. If a TBI truck has only one brake switch then you will end up hitting your brake lights and kicking off the cruise control whenever you use it. I think that the switch is still seperate on the TBI trucks, though.

    As far as the real problem, it is definately electrical, somewhere.
     
  15. backlash

    backlash 1/2 ton status

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    Blue,

    Let me get this straight! If I put a toggle in line with the brake switch, I will lose cruise control and my brake light will stay on the entire time that switch is enguaged?

    There is no way to hook up a way to disengauge to just unlock this clutch?

    As far as being electrical ... it was working fine before the rebuild ... what sort of electrical work is done during a rebuild?

    Thanks
     
  16. CaptCrunch

    CaptCrunch 1/2 ton status

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    You can accomplish the switch by tapping in where the TCC switch is on the brake pedal... this is a separate switch on all models because it does the exact oposite of the brake switch... it turns off power to the TCC opposed to turning power on the brake lights. But really... If I'm in your shoes take this back to the guy and say it's screwed up... either fix it or it is going to the dealer and when they say it is your fault it's screwed up you can pay them! Chances are when he knows you're playing hardball he'll take you very seriously and do all he can to find the problem. You could also take it to another tranny shop and have them look at it and give a full report on what they found, but I'd try the first option and see what you can get done. I believe the opposite of what someone said about it being electrical unless it is the TCC switch because the electrical circuit overrides the hydralic circuit (line pressure sw. and vac sensor) and the electrics really only controll the unlock, where as the hydralic controls lockup... To be truthful it is the first thing I would personally do is replace the TCC switch. Think of it like this... say the swicth is stuck on so it tells the converter to lock up(which is usually the case)... well if he rigged it up not to lockup in 3rd, as soon as it hits 4th it locks... you hit the brakes and cut power to the switch it unlocks... does it lock up as soon as you let off the brakes? Also it is extremely common for the switch to only malifunction when hot!

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  17. backlash

    backlash 1/2 ton status

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    &lt;&lt;If I'm in your shoes take this back to the guy and say it's screwed up ... either fix it or it is going to the dealer and when they say it is your fault it's screwed up you can pay them! &gt;&gt;

    Been there done that! Last year, this guy tried like hell to fix this thing, but then got nasty. After 10 f***ing visits he gave my money back ... saying "there's nothing wrong with this, but you won't be happy until I give you the money"! In the interim... I had to tune it up (play the game) and take time off work. Basically out $600!

    &lt;&lt;does it lock up as soon as you let off the brakes? &gt;&gt;
    Yes, immediately!

    &lt;&lt;Also it is extremely common for the switch to only malfunction when hot! &gt;&gt;

    Makes sense to me ... like the other things I tried! LOL

    Tell me though ... isn't this switch just held on by a couple of screws under the pan? Am I right that I just need to do a service and an R& R?

    Thanks Cap,

    Bob
     
  18. CaptCrunch

    CaptCrunch 1/2 ton status

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    Yeah just a couple of bolts and a wire or two hold it in. I'd just replace it with one from GM. Is easy enough to try. I suppose a wire could be shorting it, but kinda unlikely since it runs on the positive, not the ground like some other GM TCC's. Hopefully that nails your problem in the butt... Not really a whole lot else I can think of for ideas, but give a holler if you still have troubles and I'll ask around. Good Luck.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  19. backlash

    backlash 1/2 ton status

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    Now I'm really confused! Called AAMCO while I waited on your reply... the guy said the TCC switch was up by the pump I.E. have to pull the tranny!

    Is it the TCC switch or solenoid? Same thing?

    Thanks
     
  20. backlash

    backlash 1/2 ton status

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    Dorian,

    Not sure what this means.

    &lt;&lt;Well, with ALDL jumper, you can run the TCC seperate of the Vacuum and VSS...thats what I was referring to as "hokey" &gt;&gt;

    What would the end result be?

    Thanks
     

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