The Jaguar XJS V12 Manual Gearbox Conversion: The Ultimate Guide
The Jaguar XJS, a grand tourer of undeniable elegance, has long captivated enthusiasts with its iconic styling and luxurious appointments. While the V12 engine offered a smooth, powerful driving experience, the automatic transmission, while comfortable, often left drivers yearning for a more engaging connection with the road. This is where the manual gearbox conversion comes in. This guide delves deep into the world of converting your Jaguar XJS V12 to a manual transmission, providing a comprehensive overview of the process, considerations, and benefits. Whether you’re a seasoned mechanic or a passionate enthusiast considering this project, this guide will equip you with the knowledge you need.
Why Convert Your XJS V12 to a Manual Gearbox?
The allure of a manual transmission in the XJS is undeniable. It transforms the car from a comfortable cruiser into a truly engaging driving machine. Here are some key benefits:
- Enhanced Driver Engagement: The most significant benefit is the direct connection between the driver and the engine. Manual shifting allows for greater control and a more visceral driving experience.
- Improved Performance Potential: A manual transmission typically offers quicker acceleration and more responsive gear changes compared to an automatic.
- Increased Reliability (Potentially): While the conversion itself is complex, a well-maintained manual gearbox can sometimes be more reliable than the often-problematic automatic transmissions found in older XJS models.
- Weight Reduction: In some cases, a manual conversion can result in a slight weight reduction, further enhancing performance and handling.
- Increased Resale Value (Potentially): A well-executed manual conversion can significantly increase the desirability and value of your XJS, appealing to a wider audience of driving purists.
Planning Your XJS V12 Manual Conversion: Key Considerations
Before diving into the conversion, meticulous planning is crucial. Several factors must be considered:
- Choosing the Right Gearbox: This is arguably the most critical decision. Popular choices include:
- Getrag 265: A robust and reliable gearbox commonly found in BMWs. Requires significant modification for fitment.
- Tremec T5: A widely available and relatively affordable option, often requiring adapter plates.
- Tremec T56: A heavier-duty gearbox offering six speeds, suitable for higher horsepower builds. May require significant chassis modifications.
- Other Options: Consider gearboxes from other manufacturers, but ensure compatibility with the V12 engine’s bolt pattern and overall dimensions.
- Clutch System: You’ll need a suitable clutch, pressure plate, and release bearing. Hydraulic clutch systems are generally preferred for their smooth operation.
- Flywheel: A custom flywheel is often required to mate the chosen gearbox to the V12 engine. Balancing is critical for smooth operation.
- Pedal Box and Clutch Master Cylinder: You’ll need to install a pedal box for the clutch pedal and a master cylinder to actuate the hydraulic clutch system.
- Driveshaft: The driveshaft will need to be modified or replaced to fit the new gearbox. Accurate measurements are essential.
- Shifter Mechanism: The shifter mechanism needs to be positioned correctly for comfortable access. This often involves custom fabrication.
- Wiring and Electronics: The wiring harness will require modifications to accommodate the manual transmission and eliminate components related to the automatic.
- Expertise and Resources: This is a complex project. Consider your skill level and access to tools and resources. Professional assistance is highly recommended, especially for fabrication and engine management.
The Conversion Process: A Step-by-Step Overview
While the specific steps will vary depending on the chosen gearbox and modifications, the general process typically involves:
- Preparation: Disconnect the battery, drain fluids, and remove the automatic transmission, exhaust system, and related components.
- Engine and Bellhousing Adaptations: Prepare the engine block for the new gearbox, including fitting the custom flywheel and potentially modifying the bellhousing.
- Gearbox Mounting: Install the chosen gearbox, ensuring proper alignment and secure mounting.
- Clutch System Installation: Install the clutch, pressure plate, release bearing, and hydraulic components.
- Pedal Box Installation: Install the clutch pedal box and master cylinder.
- Driveshaft Modification/Replacement: Modify or replace the driveshaft to fit the new gearbox.
- Shifter Mechanism Installation: Position and install the shifter mechanism.
- Wiring and Electronics Modifications: Modify the wiring harness to remove automatic transmission-related components and integrate the new system.
- Exhaust System Reinstallation: Reinstall the exhaust system.
- Testing and Refinement: Test the system thoroughly, making adjustments as needed. Bleed the clutch system, adjust the clutch engagement, and fine-tune the overall performance.
Sourcing Parts and Expertise
Finding the right parts and experienced professionals is crucial for a successful conversion.
- Specialized Suppliers: Several companies specialize in manual transmission conversion kits and components for classic cars.
- Fabrication Shops: Skilled fabricators can assist with custom brackets, mounts, and other modifications.
- Engine Tuning Shops: Experienced engine tuners can help with any necessary engine management adjustments.
- Online Forums and Communities: Forums dedicated to Jaguar XJS owners and enthusiasts are invaluable resources for advice, troubleshooting, and parts sourcing.
Potential Challenges and Considerations
- Cost: The conversion can be expensive, with costs ranging from several thousand dollars to upwards of $10,000 or more, depending on the chosen components and labor involved.
- Complexity: This is a technically demanding project, requiring mechanical aptitude and attention to detail.
- Fitment Issues: Adapting a non-original gearbox to the XJS chassis can present fitment challenges.
- Engine Management Adjustments: Some conversions may require modifications to the engine management system to optimize performance.
- Legal Considerations: Ensure compliance with local regulations regarding vehicle modifications.
Conclusion: Embrace the Manual Experience in Your XJS V12
Converting your Jaguar XJS V12 to a manual gearbox is a significant undertaking, but the rewards are undeniable. The enhanced driver engagement, improved performance potential, and increased value make it a compelling project for the dedicated enthusiast. By carefully planning, selecting the right components, and considering the challenges involved, you can transform your elegant grand tourer into a truly exhilarating driving machine. The manual XJS offers a unique blend of classic styling, powerful performance, and a direct connection to the road – a combination that’s sure to delight any driving purist.
Frequently Asked Questions (FAQs)
1. How much does a manual conversion for an XJS V12 typically cost?
The cost varies significantly depending on the chosen gearbox, parts, and labor. Expect to spend anywhere from $5,000 to $15,000 or more, including parts and professional installation.
2. Which gearbox is the best choice for an XJS V12 manual conversion?
There’s no single “best” choice. The Getrag 265, Tremec T5, and Tremec T56 are popular options. The best choice depends on your budget, performance goals, and the level of modification you’re willing to undertake.
3. Can I do the manual conversion myself?
If you have significant mechanical experience, access to the necessary tools, and a good understanding of automotive systems, you might be able to complete the conversion yourself. However, professional assistance is highly recommended, especially for complex tasks like fabrication and engine management.
4. Will the manual conversion affect the reliability of my XJS V12?
A well-executed conversion, using quality components, can potentially improve reliability. However, the long-term reliability depends on the quality of the installation, the components used, and proper maintenance.
5. Does a manual conversion increase the resale value of the XJS?
A professionally executed manual conversion can increase the desirability and resale value of your XJS, particularly among enthusiasts who appreciate the enhanced driving experience.
