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Thread: Coyote swap 6r80 problems

  1. #1
    Tuner in Training
    Join Date
    Sep 2014
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    43

    Coyote swap 6r80 problems

    I am working on a Gen 1 coyote with a 6r80. It?s in a 1931 Ford Model A. It has a 3.70 gear ratio and a 27? tall tire. The coyote has a high rise fabricated intake but otherwise totally stock. Transmission is stock with a stock torque converter. The drivetrain is supposed to be as is from a 2014 Mustang GT.

    We installed the 6r80, harness and ECM from a supplier. We drive the car onto the trailer and to the dyno shop. We had the car tuned and from the get go the transmission shifting was not right. Brought the car back to the dyno shop and tuner suspected something was wrong with the transmission.

    Going from park to reverse or drive the transmission bangs into gear. Called the supplier and they suggested trying their MAF housing. But said the 3.70 gears is too steep and is probably causing the issue. Talked to tuner and he said it?s tuned for the MAF housing and the rear gear ratio we have. Go back and forth between supplier and tuner and decide to try another transmission thinking there is an issue with the valve body.

    Installed the transmission and built a new intake tube using their MAF housing. Put the tune back to their calibration. At first engagement into gear was smooth. Went drive the car and shifting got progressively worse. Even worse, a loud grinding noise is heard when the transmission engages 4th. Brought the car to the tuner and he is stumped.

    Supplier is dead set that the rear gear ratio is the problem because it?s causing the adaptive learning to go crazy. Told me to change the gear ratio or it will never work right. In my research I?ve seen plenty Mustangs with 3.73 or lower gear ratios, no one is saying they are having transmission issues. To test the adaptive learning theory I used my scanner to clear the adaptive learning and prevented it from learning. It did not change the way it shifted.

    The transmissions do act slightly different
    1st 6r80: slams into gear from park or neutral. Hard shifts 1-2. Hard shifts 2-3. When it shifts 3-4 the car nose dives then hard shifts. After that it shifts fine until you slow down. Manual shift mode works but shifts hard

    2nd 6r80: slams into gear from park or neutral. 1-2 shift is happening later but still hard. 2-3 shift is happening later but still hard. 3-4 has an grinding noise. We did try a WOT pull from a roll and it slipped. Manual shift mode does nothing

    We have checked the fluid more times than we can count.

    Basically I?m looking for guidance. I have the tuner telling me it?s the hardware, the supplier telling me it?s the software and me in the middle trying to relay this to a dissatisfied customer. Obviously there is something mechanically wrong with transmission 2 but that doesn?t really help with the other trans. The tune is supposed to be a completely stock tune from a 2014 mustang. The only other thing it?s been doing is throwing the CEL on for an oxygen sensor 1 bank 2 heater. They are brand new motorcraft oxygen sensors. The engine does have shorty headers.

  2. #2
    Tuner in Training
    Join Date
    Sep 2014
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    43
    Just wanted to update anyone and maybe this will help someone in the future.

    I do believe we have found the problem.

    The problem ended up being the harness was made incorrectly. At the ECU pin 35 and 38 were swapped. They are both Grey-Violet Wires. 35 is for the oxygen sensor heater on bank 2 and 38 is Transmission signal return. Once we swapped the two wires and did the relearn procedure the transmission shifts exactly as it should.

  3. #3
    Advanced Tuner skylinedan's Avatar
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    Sep 2019
    Location
    Toledo Ohio
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    224
    Good to hear, I've heard a few horror stories about people buying stand alone harnesses for the manual 5.0 set up and having issues with wires being in the wrong place like that also