Lots of Questions about 4L80E Swaps

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New member
Lansing, Mi
One note i'd like to add is the 4l80 internal wiring harness issue that they can leak. I had to replace the harness inside my transmission because it was damaged. The one I replaced it with was not of the best quality and the trans fluid would leak through the bulkhead plug and seep through the holes in which the wires passed through. I have since bought an AC Delco made wiring harness and its build so as not to leak fluid part # is 24241218 and bout $50. Id also suggest replacing the internal solenoid valves while you are in there and if you're unsure of the condition of the solenoids. Cost about $100 for a 7 piece kit.


Well-known member
Steel Soldiers Supporter
I second the leak on cheap internal wiring harness.
my first build before the TCI POS computer blew it up, the harness leaked, first rebuild guy used cheap harness.
second rebuild got the better harness, no leaks.

so when you have the tranny rebuilt, ask about the wiring harness and which one they are going to use.
I have 1009, not HMMWV but have 4l80e
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