1. Sourcing Parts: You'll need a complete manual transmission assembly, including:
* Manual Transmission: The correct transmission for your Wrangler's engine (likely an AX-5 or AX-15, but verify based on your engine).
* Clutch Assembly: Including the pressure plate, clutch disc, throw-out bearing, pilot bearing, and related hardware.
* Clutch Pedal Assembly: Complete pedal assembly, including master and slave cylinders, lines, and linkage.
* Transmission Crossmember: A crossmember designed for a manual transmission. The automatic crossmember will not work.
* Driveshaft: Possibly a different driveshaft, depending on the manual transmission and transfer case combination. Automatic and manual transmissions can have different output shaft lengths.
* Shifter Linkage and Cables: Complete shifter assembly, including linkage, cables, and boot.
* Wiring Harness Modifications: The automatic transmission's wiring harness will need modifications or replacement. You'll need to remove the wiring for the automatic transmission and potentially add wiring for the clutch safety switch.
* Flywheel: A flywheel compatible with the manual transmission. The automatic transmission uses a torque converter.
* Bellhousing: A bellhousing that's compatible with both the engine and the manual transmission.
2. Mechanical Work:
* Transmission Removal: Remove the automatic transmission, torque converter, and related components.
* Flywheel Installation: Install the correct flywheel.
* Clutch Installation: Install the clutch assembly, requiring precise alignment and torque specifications.
* Transmission Installation: Install the manual transmission, ensuring proper alignment and bolting.
* Driveshaft Installation: Install the correct driveshaft (if needed).
* Clutch Pedal and Linkage Installation: Install the clutch pedal assembly and linkage, ensuring proper adjustment and functionality.
* Shifter Linkage Installation: Install the shifter linkage and cables, properly aligning the shifter for smooth operation.
* Crossmember Installation: Install the manual transmission crossmember.
* Wiring Harness Modification or Replacement: Adapt or replace the wiring harness to accommodate the manual transmission system.
3. Professional Expertise:
* Professional Mechanic: Unless you have extensive experience with drivetrain components, this is strongly recommended. This is a complex job with tight tolerances and potential for significant damage if not done correctly.
* Transmission Shop: A transmission shop has the specialized tools and expertise to ensure the job is done right.
4. Considerations:
* Cost: Parts and labor costs will be substantial.
* Time: The conversion will take a significant amount of time, potentially several days or even weeks depending on your experience.
* Vehicle Inspection: Once complete, your vehicle will require an inspection to ensure it meets all safety regulations.
In short, while theoretically possible, converting a 1990 Jeep Wrangler from automatic to manual is a very demanding project requiring significant mechanical skill and expertise. It's overwhelmingly recommended you have this done by a qualified professional mechanic or transmission specialist. Attempting it yourself without sufficient experience could lead to serious damage to your vehicle and potential personal injury.
