6L80 behind a Hemi - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 3 Old 05-13-2017, 05:22 PM Thread Starter
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6L80 behind a Hemi

Hey Guys, just throwing this one out there. If the biggest issue regarding a Hemi swap is the transmission, why hasn't anyone fitted a 6L80 or like to the Hemi? As a Hemi owner, I'm aware that the 545RFE shifting can be " all over the joint like a mad womans shit" so what can be done about this?
If the biggest issue is "talking to the canbus" why hasn't this hurdle been jumped? Surly a tighter converter and a more progressive trans is the go?
Genuinely curious.....

Last edited by Rodjk; 05-13-2017 at 05:27 PM.
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post #2 of 3 Old 05-13-2017, 06:13 PM
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The 6L80 does not have an external controller. From what I understand, the control parameters are set in the engine computer and internal TCM are closely tied together. The 4L and 8L have external controllers. That's probably why you see the 4L transmission placed behind almost anything. The 6L is also very sensitive to the tune... Tuned correctly it's an amazing trans, but incorrect tuning can cause catastrophic failure...

Somebody with more knowledge should probably weigh in, because I don't know too much about them...
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post #3 of 3 Old 05-13-2017, 07:43 PM
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You are correct Randy, the 6l80 is a CAN driven transmission. The T43 controller in the 6l80 and 6l90 is married to the engine control module and dependent on it for it's operation. Everything from torque output to intake temperature is used by the transmission to function properly. Many attempts to run the 6l80 standalone are being made but so far what I have seen requires installing a Gen IV E38 to feed the signals into which then sends the proper CAN signals to the T43 so it can operate properly.

The 6l80 and now the 8l90 are one of the main reasons so many guys are going with the LS/LT engines​, so they can get these transmissions. It's not like the old days where you could take a 4-speed automatic and fit it behind any engine and operate it stand-alone, these CAN driven transmissions are slaved to an engine control module. I hear GM is going to release the 8-speed to be run behind the GM performance engines so that should be interesting the 8l90 does have an external TCM.


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