Thinking about swapping your K24 transmission for a T5 gearbox? You’re not alone. The K24 to T5 transmission swap is a popular upgrade for Honda enthusiasts looking for better performance and a more engaging driving experience. This guide will walk you through the entire process, from planning to final installation.
Many choose the T5 for its robust construction and wider gear ratios. It can handle more power and offers a classic, precise shift feel. While it requires some work, the result is often worth the effort. Let’s get started on your project.
K24 to T5 Transmission Swap
This swap involves replacing the original K-series transmission with a BorgWarner T5 unit, often sourced from a Ford Mustang or similar vehicle. The T5 is a rear-wheel-drive transmission, so this swap is typically done in project cars where a longitudinal engine layout is used, such as in a kit car, an older rear-wheel-drive vehicle, or a custom chassis. It is not a direct bolt-on for a front-wheel-drive Civic.
Why Consider a T5 Swap?
The T5 transmission offers several advantages over some stock gearboxes.
- Durability: The T5 is known for its strength and can reliably handle increased torque from a built K24.
- Gear Ratio Selection: A wide variety of gear sets are available, allowing you to tailor acceleration and highway cruising.
- Availability and Cost: Used T5 transmissions are plentiful and relatively inexpensive in the aftermarket.
- Shift Feel: It provides a mechanical, positive shift action that many drivers prefer.
Essential Tools and Parts You’ll Need
Before you begin, gather all necessary components. This prevents delays and frustration halfway through the project.
- BorgWarner T5 transmission (World Class is preferred)
- Custom bellhousing adapter plate (K-series to T5 pattern)
- Throwout bearing and pilot bushing/bearing
- Custom clutch disc (spline matching T5 input shaft, hub matching K24 flywheel)
- Clutch pressure plate (for K24 flywheel)
- Shortened or custom-length driveshaft
- Transmission mount and crossmember adapter
- Shifter assembly and linkage (may need modification)
- Hydraulic clutch conversion kit or cable adapter
- Speedometer cable adapter or electronic sensor solution
- Basic mechanic’s tool set, jack, jack stands, and a transmission jack
Pre-Swap Planning and Considerations
Good planning is the key to a successful swap. Don’t rush this stage.
Choosing the Right T5 Transmission
Not all T5s are the same. Identify the model you have. Key identifiers include the number of bolts on the side cover and the type of tail housing. The World Class (WC) T5 has stronger gears and syncros. Also, check the input shaft spline count (usually 10 or 26) and length, as this affects your clutch selection.
Measuring for Driveshaft and Shifter Location
Once the transmission is mocked up in the chassis, you must measure for a custom driveshaft. You’ll need to know the exact length, yoke type, and U-joint sizes. Also, check where the shifter emerges; it may need to be modified or a different tail housing used to position it correctly in your car’s interior.
Clutch and Hydraulic System Setup
The K24 uses a hydraulic clutch, while many T5 applications use a cable. You’ll need to decide how to actuate the clutch. Options include using the K24 master cylinder with a custom slave cylinder mounted on the bellhousing, or adapting a cable system. Ensure the throwout bearing matches the pressure plate fingers and the T5 input shaft snout.
Step-by-Step Swap Procedure
Follow these steps carefully. Always prioritize safety by using proper jack stands.
- Remove the Existing Transmission: Safely elevate the vehicle. Disconnect the battery. Remove the starter, clutch slave cylinder, wiring harnesses, and shift linkages. Support the engine with a jack. Unbolt the driveshaft and exhaust components that are in the way. Finally, unbolt the transmission mount and the bellhousing bolts. Carefully lower the transmission out of the vehicle.
- Prepare the K24 Engine: With the old transmission removed, inspect the flywheel and clutch. You will likely need a new flywheel or have your existing one resurfaced to match the new pressure plate. Install the correct pilot bearing into the crankshaft. This is a crucial step for proper input shaft alignment.
- Test Fit the Adapter Plate and Bellhousing: Bolt the adapter plate to the K24 engine block using the correct hardware. Then, bolt the T5 bellhousing to the adapter plate. This dry fit ensures all holes align and no clearance issues exist with the engine block or starter. Make any necessary adjustments now.
- Install Clutch Components: Mount the flywheel to the crankshaft using a new set of bolts and thread locker. Align and install the clutch disc and pressure plate using a clutch alignment tool. Torque the pressure plate bolts in a star pattern to the manufacturer’s specification. Without this tool, getting the disc centered is nearly impossible.
- Mount the Transmission: Attach the throwout bearing to the clutch fork. Carefully mate the T5 transmission to the bellhousing, guiding the input shaft through the clutch disc splines. This can be tricky; rotating the output shaft slightly can help the splines engage. Secure all bellhousing bolts and tighten them evenly.
- Install Driveshaft and Mounts: Connect the custom driveshaft to the transmission output yoke and the differential. Install the transmission crossmember and mount, which may require fabrication or an adapter. Ensure the transmission is properly supported and at the correct angle to prevent vibration.
- Connect Clutch Actuation: Install your chosen clutch hydraulic line or cable system. Bleed the hydraulic system thoroughly to remove any air, as air in the line will prevent the clutch from disengaging fully. Adjust a cable system to have the correct amount of free play.
- Hook Up Remaining Components: Reinstall the starter motor and connect its wiring. Connect the backup light switch wires to the transmission. Install your speedometer adapter. Finally, fill the T5 transmission with the recommended type and amount of gear oil—usually about 3 quarts.
Post-Installation Checks and Troubleshooting
Your work isn’t done once everything is bolted in. These final checks are essential.
Initial Testing and Break-in
Before driving, press the clutch pedal several times to ensure feel is consistent. With the car off, try shifting through all gears. Then, start the engine with the clutch depressed and the car in neutral. Listen for unusual noises. For the first 500 miles, avoid aggressive shifting and high RPM clutch dumps to allow the new clutch to seat properly.
Common Issues and Solutions
- Clutch Drag/Grinding Gears: This often means incomplete disengagement. Check for air in the hydraulic system, incorrect clutch fork geometry, or an over-extended slave cylinder.
- Vibration Under Acceleration: Likely caused by incorrect driveshaft angles. Measure the working angles of the driveshaft at the transmission and differential; they should be within 1-3 degrees of each other.
- Shifter Feels Notchy or Stiff: The transmission may be low on fluid, or the shifter linkage might be binding. Re-check the fluid level and inspect the shifter mechanism for proper alignment.
Frequently Asked Questions (FAQ)
What vehicles does the T5 transmission come from?
The T5 was used in many Ford vehicles like the Mustang, Thunderbird, and Ranger, as well as in some GM models like the Camaro and Firebird in the 80s and 90s.
Can I use my stock K24 clutch?
No. You need a hybrid clutch disc. The friction side must match your K24 flywheel and pressure plate, but the splined hub must match the spline count and diameter of the T5 input shaft.
Will my K24 ECU work with the T5 swap?
Yes, the engine’s ECU controls fuel and ignition, not the transmission. For a manual swap, you may need to bypass or trick the neutral safety switch if your car was originally an automatic, but the engine management remains unchanged.
How much does a K24 to T5 swap cost?
Costs vary widely. A used T5 can be $300-$800. The adapter kit, clutch, driveshaft, and miscellaneous parts can add another $1500-$2500. Doing the labor yourself saves significantly compared to shop rates.
Is the T5 stronger than a K-series transmission?
In a rear-wheel-drive application handling moderate torque, a World Class T5 is generally considered stronger than many stock Honda transaxles, especially for high-torque, boosted K24 builds. But it has its own limits, usually around 350-400 lb-ft of torque.
Do I need a different rear end (differential)?
You should match your final drive ratio to the T5’s gear ratios and your tire size. Your existing differential may work, but its gear ratio might not be ideal for performance or highway driving. Calculating your desired overall cruise RPM is important here.
Final Thoughts
The K24 to T5 transmission swap is a rewarding project for a dedicated builder. It opens up new possibilities for your car’s drivability and strength. While it requires mechanical skill, patience, and some custom fabrication, the process is well-documented by the community. Take your time, double-check every measurement, and don’t hesitate to seek advice from fourms where others have completed this swap. The satisfaction of a smooth-shifting, powerful drivetrain you built yourself is hard to beat.