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Thread: Automatic transmission loose wires.

  1. #1

    Default Automatic transmission loose wires.

    Hey guys I'm in the process of installing a Dominator with a 4L80E. The Holley documents show where the loose wires on the transmission harness go, except for the red/white one. I can't seem to find anything on it. I know the red/white wire is typically switched power, is it safe to assume it's the same for the transmission? Thanks for any help.

  2. #2
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    http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual - Figure 28 & 29, Page 41)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3

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    I'm going to update this thread for future reference, so others don't have this same issue. The Holley EFI Wiring Manual contains a couple errors.

    First the part number they list for the GM electronic transmissions harness in page 40 section 12.0 is 558-505, which is not the correct part number. The correct part number for the GM transmission harness is 558-405.

    Second of all, as I stated in the original post, there's no mention of the red/white wire in the wiring manual, and there's also a relay in the actual harness that's not shown in the wiring schematics in figures 28 & 29 of page 41. So my take on this is that the red wire is not switched power as mentioned in the wiring manual, but rather 12V constant battery power for the relay, and the red/white wire is 12V switched power to control the relay. This must be an update Holley made to the GM transmission harness to solve the 12V backfeed issue from the transmission to the ECU, causing the engine to not turn off when the ignition was turned off. Unfortunately, I'm not at the running stage, so I can not confirm.

  4. #4
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    I ordered the 558-405 harness last year, and it did not come with the relay. This must be a recent change to fix the backfeeding voltage problem. I had to add the relay to fix the problem.

  5. #5
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    Quote Originally Posted by 81 TransAm View Post
    I ordered the 558-405 harness last year, and it did not come with the relay. This must be a recent change to fix the backfeeding voltage problem. I had to add the relay to fix the problem.
    Yes, Holley added the transmission harness relay, and I'm glad they did. (Here's a LINK for others that aren't familiar with the previous problem.)


    Quote Originally Posted by MaddLab View Post
    Second of all, as I stated in the original post, there's no mention of the red/white wire in the wiring manual, and there's also a relay in the actual harness that's not shown in the wiring schematics in figures 28 & 29 of page 41. So my take on this is that the red wire is not switched power as mentioned in the wiring manual, but rather 12V constant battery power for the relay, and the red/white wire is 12V switched power to control the relay. This must be an update Holley made to the GM transmission harness to solve the 12V backfeed issue from the transmission to the ECU, causing the engine to not turn off when the ignition was turned off. Unfortunately, I'm not at the running stage, so I can not confirm.
    Yes, those two are wired the same way as the system relay on the EFI main harness.
    The red/white wire is switched +12V, and the red is +12V battery. See post #2 above.

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    12.0 Electronic Transmission Wiring (Holley EFI Wiring Manual LINK)
    Holley Dominator EFI currently supports the use of 4L60E, 4L65E, 4L70E, 4L80E, and 4L85E transmissions. PN 558-405 is a fully terminated harness for these applications. The following reviews installation of this harness.

    Main Transmission Connector – Simply plugs into the connector on the transmission. Located on the drivers side of a 4L80E (installed horizontally) and the passenger side on a 4L60E (installed vertically).
    Vehicle Speed Sensor (VSS)/Transmission Output Speed Sensor (OSS) – Located on the rear drivers side on a 4L80E and the rear passengers side on a 4L60E
    Input Shaft Speed (ISS) Sensor – The 4L60E does not have an ISS. It is located towards the front drivers side on a 4L80E. Note that a 4L70E has one internally wired, but is not connected to the HEFI harness. The ISS is not used for any calculations in the ECU, just for monitoring purposes.
    Brake Switch (Gray) – Wired to the brake light switch. This must be installed to a +12V source (as most brake light switches are). This input is used to unlock the torque converter when the brakes are applied.
    Ground (Black) – Connect to a good chassis/engine ground source
    Power (Red) – Supplies power to the transmission solenoids via the transmission harness relay. This should be connected to a +12V power source (must be capable of supplying 5 amps).
    Relay Trigger (Red/White) − Supplies switched/keyed +12V power to the transmission harness relay.

    NOTE:
    The power supplying this wire must NOT be tied to the same point that the ECU switched power wire (red/white wire) is connected to. If they are tied together, the transmission power will back-feed power to the ECU and the ECU/engine will not shut off when the key is turned off. Use a relay or separate switched ignition power pickup point to supply power to the transmission harness (old transmission harness without relay).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  6. #6

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    I'm in the process of wiring up a Terminator Stealth right now and the transmission harness does have the large relay installed. Does this mean I don't need an additional relay in the solid red/+12V wire mentioned in the other post? If I feed that solid red transmission harness wire from a constant/BATT +12V source, that should satisfy the requirement to keep if from backfeeding the ECU? Or is it still an issue and add another relay somewhere to kill power to the solenoids? Thanks, Joe T
    Last edited by jft69z; 04-15-2020 at 03:30 PM.

  7. #7
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    No, you don't need an additional relay. Holley revised their transmission harnesses with the integrated power relay.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  8. #8

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    Perfect, thanks for the quick reply! Joe T

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