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97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

This is a discussion on 97 2wd Suburban 4l60e, I need to lock the torque converter by any means! within the Technical / Maintenance forums, part of the General Discussion category; I need to cross country next week and will force it locked some way / some how if I have ...

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    97 2wd Suburban 4l60e, I need to lock the torque converter by any means!


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    I need to cross country next week and will force it locked some way / some how if I have to!

    I swapped in another ~97-00 good transmission, proper later model (removable bell, PWM stamping on the front of the pump) and matching converter. 3 different times in the last 3 weeks since the install, I've had lock up and one of those times thought to try cruise and it worked. Otherwise, no cruise or lockup. Suspected the brake switch, no big deal.....

    I replaced the brake switch last night and checked all the fuses, still nothing. Then I manually tried to ground the tan/black wire (PCM C1 pin 10 TAN/BLK TCC Solenoid Control 422)
    that should be for the TCC clutch but apparently that's not enough to lock it in this case. I know from the little arc/ nice coil flyback spike I got when I disconnected it from ground, that the other end of that wire likely goes to a coil/solenoid that has power on the other end!

    Now I'm looking at the TOT (transmission over temperature) sensor values and read that at over ~280? degrees the PCM will lock the converter in 2/3/4 to try to reduce temperature. Somewhere in the 20-80 ohm range I'm betting I can force the PCM to read such a high value, but I'd REALLY like to get it to lock without having to look at the check engine light!

    If someone has the full wiring diagram including brake switch, I can start digging to see if something else is wrong before I hack into the temperature sensor wiring.

    The next thing I'll try is ANOTHER new brake switch but I doubt it'll make a difference. If I can get in to borrow a good live-data scanner, I'll also check that out but I'm not holding my breath on that one either.

    Thanks for any advice!
    Last edited by Faster7; 06-01-2011 at 06:48 AM.
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    what are the codes? pm an email address, i will send you a electronics troubleshooting guide for the 4l60e.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    It was clear of codes until I unhooked the TCC wire last night and had it ran where I could manually ground it while out on the highway. I haven't scanned it to see what code it saved with that wire unhooked but I can suspect! :) I should be able to get it on a scanner tomorrow after work.
    Last edited by Faster7; 06-01-2011 at 10:39 AM.
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    I think over lunch I'm going to unhook the trans temp signal and see what that does. One source suggests that fail safe mode for that will be to do the same thing as if it's hot, so it should try to be more aggressive with locking in either 3rd or at least in 4th. Not sure any of that would bypass the brake switch portion, which will be the next thing I'm thinking about unplugging....
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Unhooked TCC brake switch input wire from PCM, no change.
    Then unhooked transmission temp signal wire from PCM, again no change.

    After work I'll try it with the brake switch wire hooked up but not the transmission temp wire.

    I don't want to believe it until I see it on the scanner..... but it really might be internal to the transmission. Never seen one do that so intermittently and have no sign at ALL of trying to lock.



    "The TCC brake switch is a normally closed switch when the brake pedal is in the released position.When the brake pedal is depressed, the switch is open and the PCM commands TCC release."

    Ok scratch that.... Next thing I'll try is manually closing the TCC brake switch pin (to ground? 5v? Will have to dig some more) since it needs to be normally closed. :)
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Unhooked TCC brake switch input wire from PCM, no change.
    Then unhooked transmission temp signal wire from PCM, again no change.

    After work I'll try it with the brake switch wire hooked up but not the transmission temp wire.

    I don't want to believe it until I see it on the scanner..... but it really might be internal to the transmission. Never seen one do that so intermittently and have no sign at ALL of trying to lock.



    "The TCC brake switch is a normally closed switch when the brake pedal is in the released position.When the brake pedal is depressed, the switch is open and the PCM commands TCC release."

    Ok scratch that.... Next thing I'll try is manually closing the TCC brake switch pin (to ground? 5v? Will have to dig some more) since it needs to be normally closed. :)
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    hopefully the guide i sent will give you some info.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    On pin #10 there is a tan/blk wire. Ground this wire to engage the TCC lock up. You will have 12V with the key on, and 0V when the TCC locks via the computer.

    This will throw a code and illuminate the check engine light. If the trucks wants the TC unlocked and you have it 'forced' it will throw P0740.

    If you have 12V on the wire with the key on and the TC doesn't lock when you ground it then replace the solenoid in the trans (accessible by dropping the pan and ~$50 at the dealership). My truck got to where it wouldn't lock and the solenoid was the culprit.

    ;97 GMC K1500

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Quote Originally Posted by boogie_4wheel View Post
    On pin #10 there is a tan/blk wire. Ground this wire to engage the TCC lock up. You will have 12V with the key on, and 0V when the TCC locks via the computer.

    This will throw a code and illuminate the check engine light. If the trucks wants the TC unlocked and you have it 'forced' it will throw P0740.

    If you have 12V on the wire with the key on and the TC doesn't lock when you ground it then replace the solenoid in the trans (accessible by dropping the pan and ~$50 at the dealership). My truck got to where it wouldn't lock and the solenoid was the culprit.

    ;97 GMC K1500

    I'm going to try that again tonight, this time leaving the TCC wire hooked to the PCM as I ground it instead of disconnected as I did last time.

    Drove ~70 miles after work yesterday with the temp sensor unhooked. Still no locking. When I got back near home, I read/cleared codes. Between there and home, short trip, no locking.

    This morning before I even get to the gas station ~1/4 mile away from home, it locks in manual 3rd and feels GREAT. Got gas. Next short stretch, same thing, ~35-45ish mph in 3rd, locks up and feels solid. 3rd short stretch after a stop light, it locks again. I drive it ~1 mile locked and come to a hill, so I throttle on to see what it does. It holds as long as I'd expect, and then cleanly unlocks. My luck , this is right before I'm going to get on the interstate for a 35 mile drive.... as after that forced unlock with the throttle I've not been able to get it to lock again, in manual 3 or overdrive either one. About 5 miles down the interstate I get the check engine light, likely for the trans temp high I've forced by unplugging that wire.

    Codes last night:
    PO740 TCC CIRCUIT MALFUNCTION -----Sure, I unhooked it when I tried forcing it to ground. ;)
    PO713 Trans temperature high etc..-----Sure, I unhooked it and I believe this confirms fail-safe is "high temp" ;)
    P1870 TRANS COMPONENT SLIPPING ---Hmmmmm it's always felt perfect since this trans has gone in... HOWEVER it does have the factory high stall V6 converter in it and without another speed sensor like the 80e's have I could see this as a possible issue with the 'dumb' old black box pcm. ;)

    I'll scan again during lunch or after work (all the places I used to be able to use a good live data scanner.... are not available this week when I need them the most!!!) and confirm it's again the high temp code, clear it out, and see what happens.

    Seriously considering having a 411 pcm flashed and shipped to my destination for me to repin and try out on the drive home, that is if I don't get it to consistently lock before I leave. I did have a deep aluminum pan show up yesterday so maybe I'll replace the TCC solenoid while I'm in there this weekend just to see......
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Reading more about P1870... I've never had the harder 1-2 shift some describe after having the code caused by a worn TCC PWM valve bore / leak. I'll still try anything in the trans that is accessible without pulling the valve body but thought anything further, I'd have another one built or park it until I can put the 4l80e in. Frustrating!

    I guess I can put down my purse ;) and do the whole shift kit myself, as I get the feeling that no matter what I see on a live data scanner, it's really going to come down to something internal now, the P1870 seems so common and some of it's symptoms might match my issues. Although I NEVER got a check engine light before I started unplugging wires. :) :)
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    double post
    Last edited by Faster7; 06-02-2011 at 09:13 AM.
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    A little follow up to your posts. When my TC stopped locking, it was when it was warm as well. It seemed like there wasn't a problem when the truck/trans was cooler. A couple things I have noticed with my truck (5.7/60E/3.73 gears) is that I can get lock under light load above 40mph and lock at any throttle position above 75mph (other than 0% throttle).

    I can't guarantee this but I'm thinking that the solenoid is bad. The only difference that I can tell between your truck and mine is that I never got any codes (no 1870). I put a few hundred miles on the truck with the issue till I figured out what the problem was and even then I wasn't sure it was the solenoid until after I replaced it. You do not need to remove the valve body to replace the solenoid, just the pan. It is almost as simple as replacing a headlight bulb; unplug old and remove install new and plug in.

    Also when I did my grounding of the TCC wire, I left the wire connected to the computer and just tapped it and grounded the wire. Only code I got was when the truck wanted the TC unlocked and I had it forced via grounding the wire.

    Good luck!

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Hmmmmmmm, I'll fly to the trans parts shop again before 5 to grab one (or hit the dealership near where I work if it's in stock) as that would be easy to try! I just made it by 5 today/yesterday/whatever to get the shift kit/ cork gasket / along with their "preferred" PWM "fix" kit. :)

    I'd plugged my trans temp wire back in, cleared codes, and it'll no longer throw 1870 so I think forcing it to high temp was pressing the issue? Who knows. I'll have it on a live scanner late Friday night and then pull the pan sat morning and try the TCC solenoid first and then the full shift kit next.

    Thanks!
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Dang, Oreilly's would have it without rushing but it looks like both options still have the crap plastic snout. I guess it's accessible enough I can give it a try any ways.

    $38, or $56 including the new harness.

    http://www.oreillyauto.com/site/c/de...0073&ppt=C0338

    http://www.oreillyauto.com/site/c/de...0073&ppt=C0338
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    I hurried to the highway this morning to try to keep everything really cool as that's when it seems to be fine. Then I was able to drive it for that ~6mile leg with the converter locked in OD. Very reassuring to be able to do that! I'd ease off the throttle and slow to 60 in OD, and squeeze it right back up to 80 at ~15% throttle or so and it held well, locked the whole time. Then of course it was warm enough by the time I had to exit that I couldn't get it to lock again the rest of the ~25 mile trip.

    I'm hopeful that just replacing the TCC solenoid, fresh fluid and deep pan and filter, trans cooler will fix this, but prepared to dig right into the valve body with the rest of the shift kit if it even hiccups after that first test drive.
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Before I tore into the transmission, I read codes, reset the computer, and hooked the temperature feed back up. It turned P1870 back on and this time... I did start to get the harsh 1-2 shift! Unplugged the tempature wire and the hard shift went away. This might be a GREAT temporary fix for P1870 on 4l60e's as with that fluid temperature wire unhooked it seems it over rides the high line pressure command P1870 usually would command. That might let someone drive until they can have it torn down, or if it is only an issue with TCC lock up, one might be able to "live with it" but at least the high line pressure/harsh shifts won't start destroying other parts.

    Then I started into it.... I thought I was going to just replace the TCC solenoid and harness but once I was there I went ahead and pulled the valve body and installed some of the basic Transgo kit for P1870.

    I installed their PWM "fix" that locks it on, drilled a new separator plate as per the directions.

    4th accumulator already had a needle small orifice pinned into the feed hole and I was afraid I'd push it into the case if I tried to block it so I left it, and then I guess the kit instructions there essentially flip the piston over and put the spring on the other side which I believe would also bypass that function, except that now you have fluid pressure (although not much) pushing on the separator plate. It is the better aftermarket plate and it's supported very close to that area, so I guess that's it.

    All fixed! TCC locks with authority (no PWM). Now I'm going to have to swap to 411 + tunercats so I can tune it, as with the higher stall I would likely not command lock as often as if there's a big rpm difference between unlocked and locked, it is just a bit harsh.
    '96 C1500 Silverado ECSB 4.3/4L60E 3.42 ---> 5.3/NV3500 3.73 9.5"

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    I know this thread is kind of old but I'm having a very similar issue in my 1994 GMC T15 Jimmy.

    I am getting lockup no problem under 50mph, anything above and it is locking up intermittently but mostly not in lockup.

    I have not tried above 70 but will give it a shot.

    My next step is to test the grounding of your pin10 (which I will cross reference in my service manual) to tell me if it is the lockup solenoid.

    My scanner shows lockup is commanded and engaged when it is in fact not. I can tell this by watching my vacuum gauge drop as I increase throttle with my tach rising a few hundred rpm.

    I also noticed my fuel mileage tanking over the last few months so this has been there for a while and just gone unnoticed.

    I'm hoping it is a bad tq converter so I can get a lower stall one. These s10 v6 converters are stupid high stall compared to my 96 v6 FSC.

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Quote Originally Posted by uhlhazard View Post
    I know this thread is kind of old but I'm having a very similar issue in my 1994 GMC T15 Jimmy.

    I am getting lockup no problem under 50mph, anything above and it is locking up intermittently but mostly not in lockup.

    I have not tried above 70 but will give it a shot.

    My next step is to test the grounding of your pin10 (which I will cross reference in my service manual) to tell me if it is the lockup solenoid.

    My scanner shows lockup is commanded and engaged when it is in fact not. I can tell this by watching my vacuum gauge drop as I increase throttle with my tach rising a few hundred rpm.

    I also noticed my fuel mileage tanking over the last few months so this has been there for a while and just gone unnoticed.

    I'm hoping it is a bad tq converter so I can get a lower stall one. These s10 v6 converters are stupid high stall compared to my 96 v6 FSC.
    how many miles on it?
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    purchased with 150K on the clock, shes at 229,943 right now, seems to be the original tranny.

    Now I pretty much get no lockup at any speeds.

    I tested both brake switches and all connectors and found no faults. Scanner shows the tps acting accordingly with no deviation from normal. I don't know how to read the MAP (no maf on a cpi) but the map seems in line with my vacuum gauge.


    I am not throwing a tranny at it until it is deserved. I'd rather spend the time to learn how the transmission works both mechanically and electronically anyways as a hobby.

    So far I feel that I have ruled everything out except an electrical gremlin, tcc solenoid, and TC.

    Not too sure where to go from here but my next step will be to acquire a (delco hopefully) tcc solenoid and install my Derale pan. http://www.amazon.com/Derale-14204-T.../dp/B004XONSSK

    I took a trip to San Antonio from Houston and back and noticed my transmission temperatures stuck just under 250* F with cruise set at 70mph, dropped it to 65mph and it dropped down to about 235* F sustained. Soon as I get into lower speeds like 55 and under it drops down to around 195-210 where it was normally at during lockup at 70mph.

    I have 2 transmission coolers as well. Might be a small furnace without them and no lockup!

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    Re: 97 2wd Suburban 4l60e, I need to lock the torque converter by any means!

    Installed the tcc solenoid with harness. This was a PITA because you must remove the 1-2 accumulator to remove the force motor to remove the main harness connector. I carefully removed the accumulator so as to not damage the gasket, which was mildly successful until I tried to remove the force motor which i smacked into the accumulator breaking the gasket in 3 places.


    YAY! So I went ahead and replaced the harness (that main harness connector was majorly hard to get out of the transmission with limited access to the top of the tranny (not a fullsize). Reinstalled the accumulator without replacing the gasket (it was a risk I'm willing to take) and went for a test drive. I also installed the derale pan which means I have to drop my tcase/trans xmember anytime I need to drop the pan.

    Still no lockup but my scanner reports it was commanded.

    Looking more like a torque converter. The sad part is when I removed my existing tcc solenoid I went ahead and hotwired it to a battery and it would not engage every time, very intermittent and if you smacked it a bit it would keep engaging so i dunno.

    Is that 1-2 accumulator gasket worth replacing? During the test drive it seemed to shift like normal.

    Installed the tcc solenoid with harness. This was a PITA because you must remove the 1-2 accumulator to remove the force motor to remove the main harness connector. I carefully removed the accumulator so as to not damage the gasket, which was mildly successful until I tried to remove the force motor which i smacked into the accumulator breaking the gasket in 3 places. YAY! So I went ahead and replaced the harness (that main harness connector was majorly hard to get out of the transmission with limited access to the top of the tranny (not a fullsize). Reinstalled the accumulator without replacing the gasket (it was a risk I'm willing to take) and went for a test drive.

    I also installed the derale pan which means I now have to drop my tcase/trans xmember anytime I need to drop the pan. Still no lockup but my scanner reports it was commanded. Looking more like a torque converter. The sad part is when I removed my existing tcc solenoid I went ahead and hotwired it to a battery and it would not engage every time, very intermittent and if you smacked it a bit it would keep engaging so i dunno. Is that 1-2 accumulator gasket worth replacing? During the test drive it seemed to shift like normal.

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