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Thread: 4l80e lockup slippage what is normal

  1. #1
    Tuner in Training
    Join Date
    Feb 2019
    Posts
    10

    4l80e lockup slippage what is normal

    I am tuning a 2002 2500 hd 6.0 4l80e. Original motor trans and PCM to the truck. 260K miles. I rebuilt the motor and trans this spring and I'm trying to dial it in. I am having some converter slippage/trans overheating problems that I am trying to diagnose.

    Before tearing the truck down, I had no driveablity issues. The rebuild was just a precautionary measure trying to avoid the inevitable considering the mileage. I do a long trip about every summer towing a 8k trailer cross country. I did some mods/upgrades to the motor and trans that imagine will require some fine tuning.

    List of mods just in case it is pertinent to the problem:

    Motor: .5 more compression (10:1) running 862 5.3 heads (mild bowl porting and chamber unshrouding) 2.00 intakes stock exhaust valves 208-216 113 lsa .500 .500 lift cam, NNBS intake 5.3 FF inectors, Volant cold air intake.

    Trans: Found the AFL limit valve to be worn in the valve body (used the transgo kit to restore the bore and valve), Forward drum was worn where the sealing rings ride (used Sonnax oversized sealing rings to repair) Sonnax line pressure booster kit, Sonnax TCC regulator valve with the firmer apply spring installed, Sonnax 2-3 and 1-2 shift valve springs, rollerized rear, dual fed direct drum, a few planetary lube holes drilled slightly oversized where recommended, .040 Line to lube hole drilled in the pump, all new AC delco solenoids and pressure transducer, all new alto high energy green clutches, steels, bands, bushings and thrust washers. End play set on the tight side of spec. Florida torque converter upgraded towing converter (supposed to have the failure prone lockup piston tig welded and an upgraded friction material).

    Sorry for the info overload, I just dont know exactly how the mods affect the required tune.

    Everything seems to be running fine, and I'm working on learning to tune. The trans has had 2 issues:

    At very low load flat ground at about 45-50 it bounces in and out of lockup. I've played with some settings trying to keep it locked, but no changes. Doesn't happen very often.

    I took my first long trip on the interstate the other day running 75-80 mph. I live in the hills, so it takes a fair amount of throttle to maintain speed on the hills. After about 40 miles the trans started getting hot. At low load flat ground the TCC slippage shows virtually no slippage rpm(0-5 rpm tops). As I approach a hill and begin to add throttle to maintain speed, the slip rpm climbs all the way up to around 350 rpm. The TCC PWM duty cycle shows 99.2% when this is happening.

    The VCM scanner doesn't have much in the default channel setup for trans stuff. I added the TCC PWM, engage mode, and slip rpm. I assume folks will want a log file to help troubleshoot. Is there any other things that I need to add to the log to get good data?

    Any help would be appreciated.

    Lynn

  2. #2
    Tuner in Training
    Join Date
    Feb 2019
    Posts
    10
    I bumped up the TCC PWM min duty cycle to 80% and the max to 99. I also changed the TCC bias or whatever it is called. It is under the shift pressure tab. It seems to have helped, but the problem has been a little sporatic. I am going to take a long trip on Sat and see if it holds better.

    I have done some reading about playing with the force motor tables to raise pressure, but I am hesitant. Lowering the value raises pressure correct? This thing has more torque at part throttle than stock. Maybe I need more commanded line pressure.

    Lynn

  3. #3
    Tuner in Training
    Join Date
    Feb 2019
    Posts
    10

    Current tune

    This is the first time I have attempted to attach a tune. Hopefully it stuck. I will dig through my logs and try to find when it is slipping.

    The parameter i adjusted is the TCC offset under steady state pressure control. There is also a clutch gain for when it the TCC is locked, does it do the same thing a different way?

    Lynn
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    Last edited by racin69z; 2 Weeks Ago at 08:33 PM.