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any tranny experts here? electronic problem

Discussion in 'Chevy Trucks' started by Detroitdan, Sep 14, 2007.

  1. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    I've been working at solving some electronic problems for months now. I lost OD and lockup, changed ECT, TCC solenoid, brake light switch, rebuilt valve body with Sonnax kit, 1-2 3-4, and 2-3 shift solenoids, cleaned vssb.

    After doing the Sonnax Sure Cure, I got OD and lockup back, everything worked perfectly. For a half hour or so. Then lost it again. After changing the shift solenoids I got OD (4th) back. But the TCC lockup is intermittent. Most of the time I lose lockup after about 5 minutes of driving.

    Last winter trans shop told me tranny is blown and I need a new one. Fluid has never been burnt, nothing ever in the pan to indicate mechanical failure, and since I have been able to get everything back temporarily, I am 100% certain that it is an electronic problem, not a broken hard part.

    Most recently it occurred to me that the problems started around when I had the remote starter installed too. Got thinking about it, and realized the starter is tied into both the ignition switch and brake light switch, both of which have some ties to the TCC operation. I turned off the remote starter by the little toggle switch that powers it. Again, the tranny began to work perfectly, even when towing. After a week of euphoria, the TCC started acting up again. Been trying to get wiring info for the remote starter as I suspect it may be involved.

    Only other thing I can think of is the torque converter itself or just a bad wire or ground somewhere in the tranny control harness.

    Also, I have changed the fluid many times, but I havent had any of the GM Lubeguard additive to add. I did it a long time ago, but I'm sure it's long gone now. Is that stuff really important?

    It is a 97 4l80e 4wd.
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Dan, did you disconnect the battery every time you dug into the tranny when you replaced the solenoids and did the Sonnex fix??
    Have you scanned the truck yet to check for codes in the powertrain managment?
     
    Last edited: Sep 15, 2007
  3. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    No on disconnectiong the batteries, but I did that the other day to clear the codes and also to change a weak battery terminal. I had it scanned and only got P1870, which is ECM detecting trans slippage.
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Has disconnecting the batteries had any affect at all on the operating characteristic of the trans?

    BTW, an 1870 code is specific to torque converter slippage and not to the trans itself slipping. It's easily set by the ECM and would definitely be cause by the lock up problems your experiencing so as I think you've already suspected, it's not much help to troubleshooting the problem.
     
  5. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    I'm not sure about the disconnecting of the batteries affecting the trans. If it did I didnt realize it. I did notice the truck ran like a scalded ape after I cleared the codes and installed a new terminal where I had one that was making a questionable connection. I changed the fuel filter at the same time, so I thought it was due to that, or possibly to a stronger voltage but wasn't sure why. Maybe it was the truck coming out of limp mode? But I cant remember if it lost lockup that day or not. It is definitely doing it now though, just about exactly 5 minutes into my drive to or from work, suddenly for no reason it just unlocks.
    I was wondering about the torque converter clutch being damaged. There was one event that happened last winter that I thought may have cooked it, it was starting to act up here and there, but after I pulled out a stuck truck it was pretty much constant. I thought I may have overheated the T/C with several minutes of non-stop flogging. I pulled the cover and looked at it, didnt see any discoloration from heat.
    But I keep going back to thinking it's electrical, like I said shutting off the remote starter got me my whole transmission back, lockup and all, but only for a week. I'm in contact with the guy who did the install and hes trying to guide me through troubleshooting that.
    I have thought several times I might replace the torque converter, but that is a WHOLE lot of work for something that may or may not cure the problem. I've also been wanting to replace the ecm with a Heath max-e-tork, but I'm hesitant to spend the money when the tranny is ill. Be nice to know if the ecm was the problem.
    That;s another thing, I have an electronic shift kit tied into the ecm, but it's been there for years. I rechecked all those connections the other day and they looked fine. I actually leave that turned off now because when I did the Sonnax I changed a spring that gave me real hard shifts. 1-2 anyway.
    Thanks for the help, I really appreciate it.
     
    Last edited: Sep 16, 2007
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    I tend to agree with you that it is an electrical issue. When it will lock up does the lock up feel strong or like it's slipping or struggling to lock up? The friction surface in converters can get warped from abuse or an over heat situation and if it slips too much the ECM will disable the lock up feature to protect the converter and trans from building too much heat due to slippage.This is what is refered to as the "limp mode" (like you mentioned). That's the only way I would say its a mechanical problem and not an electrical issue.
    Clearing the codes will usually make the truck work good for a while since it's no longer in limp mode.
    The fact that you consistently loose the lock up 5 minutes into a drive could be related to the remote starter as they do have built in timers to control the run times and such. I think the first thing I'd do is go over every single ground point on the truck and closely examine the wiring harness from the firewall down to the trans and if I didn't find any problems, I'd then totally remove the remote starter since it could definitely affect the trans functions as you suspected.