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Q: What happens if I unplug my transmission?

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If I unplug my transmission will it cause any issues beside horrible gas mileage? My transmission lost all the fluid yesterday, but I put more in as soon as that happened and it's still holding. I wasn't sure if it was the gasket. But I was told that the transmission has an overflow tub and that if it gets to warm the fluid will flow out. But if I unplug my transmission will my truck (4L60E) still shift right and I won't take a risk of screwing it up?

My car has 157896 miles.
My car has an automatic transmission.

A: Hello and thank you for contacting YourMech...

Hello and thank you for contacting YourMechanic. The 4L60E has electronic shift solenoids that shift the transmission in first, second, and fourth. If you unplug the harness to the transmission, your transmission will only have reverse and third gear.

In the event the transmission looses power to the solenoids, the transmission goes into limp mode which is third gear, for it is a mechanical gear only. Plus, the torque converter clutch will not work for it has an electronic solenoid that operates the circuit to apply the converter clutch.

My recommendations is to leave the plug on the transmission. The instant the plug is disconnected, the engine light will come on for the computer not communicating with the transmission. If your transmission is holding the fluid and is working fine, then it is good.

Check the transmission fluid with the engine running and at cold temperatures along with operating temperatures for proper oil level. If you need assistance with your transmission fluid, then seek out a professional, like one from YourMechanic who can help you with your vehicle.

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