Do I need to pull the transmission controller out for a JK LS swap?
No - there is no external transmission controller to pull on a 6L80/6L90 swap. The T43 TCM is bolted to the valve body inside the transmission pan; the E38 ECM talks to it over CAN, so wiring is just CAN in/out, brake signal, power, and ground. If you need it bench-programmed, drop the pan, unplug the two connectors, pull the selector-shaft nub, remove the 6 module bolts, then the 11 bolts separating the module from the valve body (E12 external-Torx-Plus socket), and send only the module - not the valve body. If you run a 4L65 instead, the Gen III PCM controls it directly with no separate controller, while a Gen IV engine with a 4-speed needs an external T42 TCM added to the CAN network.
Last updated
Who this applies to
- Computers: E38, E67
- Engines: L92, L94, LS3, LH6, any Gen IV 58x
- Transmissions: 6L80E, 6L90E, 4L60E, 4L65E
- Not for: Gen III 24x with 6L80 (not supported - 6L80 needs a Gen IV controller)
6L80/6L90 with E38 - programming the internal T43
- Remove the pan, pull the tab to unlock the module from the electrical pass-thru, and unscrew the 6 module bolts 6 bolts
- Unplug the two electrical connectors, disconnect the selector shaft nub, and remove the 11 bolts to separate the module from the valve body 11 bolts + E12 external-Torx-Plus socket
- Ship only the module with the 4-digit alpha-numeric code from the transmission ID tag - the first digit is the model year of the transmission module only, no valve body
6L80/6L90 - wiring (nothing external to mount)
- Wire it like a CAN transmission: the TCM built into the valve body makes wiring very simple - basically CAN in and out, brake signal and power and ground CAN + brake + power + ground
4L60E/4L65E behind a Gen III engine
- With a Gen III PCM, no separate controller exists - the PCM controls the 4L65 directly (with the extra IMS/PRNDL/solenoid wiring that entails) PCM-controlled, no TCM
Careful
- Do not send the valve body with the TCM - ship only the module plus the 4-digit alpha-numeric code from the transmission ID tag (first digit is the model year)
- Keep the 4-seal assembly in place when removing the module or the transmission will lose pressure control
Go deeper
Check this first
- Confirm which transmission you have: the 6L80's controller is a T43 inside the trans; there is no external box to find or pull
- Confirm the engine/PCM pairing: a Gen III PCM controls a 4L65 directly, while Gen IV engines with 6-speed CAN transmissions use the internal TCM over CAN
Try this, then this
- Transmission stuck in limp after install - confirm the T43 calibration matches the vehicle and the two internal connectors are fully seated — the TCM must be programmed for the swap and its pass-thru connectors are easy to leave loose. Worked if: all gears engage with no pressure-control codes
- No communication with the trans - check CAN wiring, brake signal, power, and ground at the trans connector — the internal TCM needs all four to talk to the E38. Worked if: scanner sees the T43 on the CAN bus
How you know it's fixed
- TCM communicates with the E38 over CAN with no U-codes
- Transmission shifts all gears with correct line pressure and no slip codes
- No reduced-power or transmission-hot warnings
Key numbers
| What | Value |
|---|---|
| T43 mounting location | internal to valve body |
| Module-to-valve-body bolt count | 11 bolts |
| TCM bolt socket | E12 external-Torx-Plus |
Every option we know of
| Maker / product | Part # | Fits | Price | Where | Status / notes |
|---|---|---|---|---|---|
| MoTech JK LS swap kits (harness, mounts, tuning) | varies | JK Wrangler LS swaps, Gen IV + 6L80/6L90 | not listed | In production Gen III engines not supported (not emissions compliant) | |
| PSI (Performance Systems Integration) T43 TCM bench programming service | 6L80E/6L90E T43 modules | not listed | psiconversion.com | In production do not send the valve body | |
| EFI Conversions T43 TCM transmission connector pigtail | 100-00886 | 6L80E/6L90E T43 harness connection | ebay.com | none noted |
Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.