Transmission & Clutch
The Gen Coupe accepts both manual and automatic LS transmissions with the correct adapter, crossmember, and driveshaft. Common choices are the T56 Magnum XL (manual) and 4L60E / 4L80E / 6L80E (automatic).
T56 Magnum XL
Requires a custom pilot bushing since it uses a Ford input shaft — unless you get the GM shaft.
- Pilot bushing: McLeod Racing 8-1094-2 — Oilite, GM except Pontiac, 1.094" OD x .672" ID
- Clutch alignment tool: RAM 26-spline clutch alignment tool
Magnum XL (GM) Specs
| Torque rating | 700 lb-ft, 7,800 rpm max |
| Ratios (TUET18131) | 2.66 / 1.78 / 1.30 / 1.00 / 0.80 / 0.63, rev 2.90 |
| Ratios (TUET18132) | 2.97 / 2.10 / 1.46 / 1.00 / 0.80 / 0.63, rev 2.90 |
| Input / output | 26-spline input (6.5" long) / 31-spline slip yoke |
| Electrical | Electronic speedo output, reverse lockout solenoid, reverse light switch |
| Fluid | 3.66 qt: Tremec HP-MTF, Synchromesh, or Dexron III ATF |
| Weight | ~150 lb dry |
The 2.66 first gear suits higher-power and boosted cars; the 2.97 gives a stronger launch with a mild N/A engine.
Shifter
The T56 shifter lands in a different spot than the stock Genesis shifter. Expect to notch the tunnel or shifter plate. ISR sells a T56 Genesis shifter relocation kit (IS-GNLS-SHFT), and one LS1 build used a Hurst short shifter, GTO shifter cup, and a shifter extension.
Other Transmission Options
- TR6060: supported by Sikky's trans mount and driveshaft options.
- Keep a Nissan Z33/Z34 6-speed: LOJ's Z33 kit includes an adapter plate, Clutchmasters billet flywheel (350Z/G35 clutch), mini starter, and shortened 350Z-style linkage.
- Automatics (4L80E, 6L80/6L90): LOJ sells trans mounts for these. Automatic control needs a Terminator X Max or a separate controller. LOJ warns that GM transmissions may require tunnel modification.
Reverse lights and speedo for the T56 are covered under Wiring and ECUs & Tuning.
Clutch Master Cylinder
You'll need a Wilwood master cylinder with an adapter from ISR. Two small issues I found:
- Add a thin rubber washer behind the clutch pedal pin, and file down the cylinder mounting portion so it sits flat on the washer and pedal.
- Cut the rubber dust boot that comes with the Wilwood master cylinder so it fits behind the Wilwood adapter. This helps preserve the cylinder's life.
Community & Parts Links
- Swapped GCs (Facebook)
- Genesis Coupe LS Swaps (Facebook)
- All-year shop manuals & wiring diagrams (Google Drive)
- Sikky LS swap kit
- LOJ Conversions
- ISR Performance mounts
- Jason Riddle / Dream Machine Z
Sources & further reading
- Shift SST — Tremec Magnum XL (GM) features and dimensions
- LOJ Conversions — Genesis Coupe LSx Basic Swap Kit (Z33 6MT)
- LOJ Conversions — Genesis Coupe LS transmission mounts
- ISR Performance — Genesis LS mount kit (shifter relocation kit listed)
- Super Street — LS1 Genesis Coupe (T56 shifter notes)
Prices and part numbers were checked in October 2026 and can change. Always confirm with the vendor before ordering.