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How to wire a 4L80E transmission for manual shifting without a controller

Article/photo's courtesy of
Volcano Manifolds
4L80E Full Manual Wiring-1 pdf.png

The GM 4L80E transmission was produced from 1991 - 2009 in factory vehicles, they still sell it from GMPP. However, they changed the connector in 1993, this connector is from 1993 on. The service manuals state the older vehicles have to be updated to this connector by replacing the internal harness and external connector from the 93 on retrofit kit, which is common during rebuilds.

Also, the main purpose of this mod is if you do not have an expensive controller, you can wire it this way to use it manually for free. So if you have a controller, there would be no reason to bypass it to do this, you could still shift it manually with the controller.

This diagram is viewing the vehicle harness connector that plugs into the transmission.
Be sure to utilize the correct wires out the back of the connector, the wires will be mirrored.

Do this at your own risk! Disconnect vehicle battery before any modifications!

To Wire Externally for Manual Shift without a computer:

- Supply a switched +12V source with a fuse to turn on with the ignition key at the 12 V IGN terminal.

- Combine and splice PSM #1, PSM #2, and SOL A together. PSM #1 and #2 will operate SOL A.

- Splice PSM #3 with SOL B. PSM#3 will operate SOL B.

- Using a switch to ground the TCC wire will apply the lockup torque converter clutch. (optional)

The transmission will now be in whatever gear is selected with the shifter manual valve. It will not shift
automatically. No internal mods are required, the trans will default to full pressure all the time.

You can also monitor the trans fluid temp by supplying 5V for the temp sensor and reading the temp out
terminal if you have a gauge that can do that.

Note: Without any connector, the transmission should operate in Park, Neutral, Reverse, and 2nd gear.
This is a fail-safe to drive somewhere for help if the electronics fail, it can also test basic trans function.
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