Wicked Wrench Motorsports

Jeep JK/JKU — Gen V LT Swap

Complete Installation Guide — Compatible with GM 6L, 8L, and 10L Automatic Transmissions

Disclaimer: This guide is provided for reference and educational purposes only. Engine and transmission swaps carry inherent risks. Always verify fitment, torque specifications, and safety requirements for your specific vehicle before beginning work. Wicked Wrench Motorsports assumes no liability for damage or injury resulting from the use of this information. Use at your own risk.

✅ Transmission Compatibility: This installation guide applies to all GM automatic transmission families used in Gen V LT swaps — including the 6L80, 6L90, 8L80, 8L90, 10L80, and 10L90. The mounting, linkage, and plumbing procedures are the same across all units. Refer to the individual transmission-specific guides for fluid specs and internal conversion procedures.

1. Intake Manifold Trimming

Trim the structural plastic ribs off the back of the Gen V LT Truck intake manifold. Alternatively, use a modified LT2 intake (suggested). Go slow — applying too much pressure can crack the intake housing.

2. Tail Housing Modification

Mount the adapter onto your transfer case to determine your desired clocking position. Insert the bolts and test for a perfect fit before committing.

3. Transfer Case Integration — Critical Order of Operations

Bolt the transfer case to the transmission first, before moving to the mount.

1. Upper Block Plates

Bolt the upper motor mount plates directly to the LT engine block. Ensure the flat side faces down.

2. Identifying Saddle Brackets

Locate the stamped letters on the motor mount saddles:
• Stamped (D) = Driver Side (Left)
• Stamped (P) = Passenger Side (Right)

Orient both saddles so the bolt holes face toward the vehicle frame. You may need to slightly spread the factory frame tabs apart to slide the saddles into place.

3. Mounting Hardware & Safety

Secure the saddles to the frame using the four supplied M12 x 1.75 bolts and 2 M12 x 1.75 nuts. Reuse your 2 original Jeep Ripp Lock Washers on the other 2 saddle mount bolts — this prevents the bolts from loosening and slipping through the frame mounts.

Drop the hydraulic motor mounts into the saddles and hand-tighten the supplied M12 x 1.75 serrated face nuts on the bottom side.

1. Setting the Drivetrain

Lower the LT engine and transmission assembly into the frame bay. Bolt the supplied transmission plate to the crossmember and transmission — the wide side bolts to the Jeep crossmember using the two supplied M12 x 1.75 bolts, washers, and nuts; the small side bolts to the transmission mount.

Push the entire engine/transmission assembly as far back toward the firewall as possible. Leave all mounting bolts loose for now to allow for adjustment.

2. Firewall Modification (Clearancing)

Lower the Jeep body back onto the frame to mark exactly where the intake/engine head contacts the firewall. Lift the body back up and carefully clearance the marked spots using a hammer or body tool. Repaint the exposed metal to prevent future rust.

3. Final Drivetrain Alignment

Lower the body back down permanently. Align and center the transfer case perfectly within the chassis driveline hoop. Lock down and fully tighten all motor and transmission mount bolts.

📸 Important: Only after the body, engine, and transmission are completely mounted should you measure for your new custom front and rear driveshafts so you can get them ordered.

1. Shifter Linkages

• Mount the conversion transmission gear shift bracket to the left (driver) side of the transmission.
• Modify the transfer case shifter following the Advance Adapters Kit #715596 instructions, then hook it up to the supplied transmission T-case bracket.
• Attach the factory JK transmission cable to the newly supplied transmission shifter bracket.

2. Pedal Assembly Swap

• Remove the three 10mm nuts securing the stock Jeep JK accelerator pedal. The 3rd hidden nut can be stubborn — don’t worry about damaging the old plastic pedal during removal as it is not being reused.
• Remove the bottom stud on the Jeep firewall.
• Install the new supplied bracket using the upper Jeep stud and supplied lower 6mm bolt (where you removed the stud).
• Place the modified supplied electronic accelerator pedal on the top stud and the new bracket stud, then tighten using the factory 6mm (10mm socket) lock nuts.

3. Steering & Clearances

• Reconnect the steering shaft and check for manifold interference.
• If necessary, push the engine slightly side-to-side within its loose mount tolerances to clear the exhaust.
• Gently bend the engine oil dipstick tube forward to ensure it clears the spinning steering shaft.

1. Harness & Computer Layout

• Remove the factory Jeep ECU. Install the provided custom ECM and fuse panel bracket in its place, then mount the new units.
• Lay in the new engine/transmission wiring harness. Route it cleanly up the center of the transmission, keeping it completely clear of hot exhaust components.
• Install the transmission and transfer case vent tubes. Zip-tie the harness and vent lines together neatly along the top center of the transmission.

2. Power Steering (P/S) Plumbing

If using a remote reservoir, mount the PSC bottle bracket directly to the brake booster/master cylinder area.

Plumbing Route:
• Pressure line → front port on the steering box.
• Rear port of steering box → bottom port of P/S cooler.
• Top port of P/S cooler → P/S reservoir bottle.

3. Transmission Cooler Plumbing

Mount your external transmission cooler.

Plumbing Route:
• Front transmission outlet → bottom port of cooler.
• Top port of cooler → rear transmission port.

4. Coolant & Heater Hoses

• Upper Radiator Hose (#23283): Cut to fit using the best-contoured portion of the hose.
• Lower Radiator Hose (#22777): Cut to fit utilizing the sharp “U” shaped section.
• Heater Hoses: Route the 5/8" (#80406) and 3/4" (#80417) hoses smoothly to the core. Keep them completely away from sharp body edges and exhaust heat to prevent chafing leaks.
• Note: Factory Jeep uses 5/8" for both inlet and outlet. Use Gates 5/8" to 3/4" heater hose adapter P# 28611 where needed.

• Build and hook up the main battery cables and chassis grounds.
• Fill the engine with oil, fill the cooling system, add your transmission baseline fluid, and check for immediate leaks before turning the key.

⚠️ Aluminum Radiator Grounding Warning

If you are using an aluminum radiator, strongly recommend adding a dedicated ground wire directly to the radiator tanks. Ensure the engine block, frame, and body all share a clean, paint-free common ground network to prevent electrolysis. Use GM Coolant Tabs (ACDelco #12378255) in the cooling system.

💡 Wicked Wrench "Pro Tips"

Order of Operations Matters: Transfer case before transmission mount, body on before measuring driveshafts, engine loose before firewall clearancing. Skipping the sequence costs you hours of backtracking.

Intake Choice: The modified LT2 intake is the cleaner solution for firewall clearance. If you go with the trimmed truck intake, take your time with the ribs — a cracked intake housing is an expensive mistake.

Driveshaft Timing: Do not order your driveshafts until everything is fully bolted down and the body is permanently seated. Even a small shift in engine position changes your measurements.