1. Parts Acquisition:
* Posi-Traction Differential: This is the core component. You'll need to find one that fits your Mustang's axle housing. The '65 Mustang used either 8-inch or 9-inch rear ends depending on the engine and options. Identifying your existing rear end is crucial. Look for casting numbers on the differential housing to determine the size. You can also find this information on the car's build sheet (if you have one) or through decoding the VIN. You'll want a used posi-traction unit, as new ones can be very expensive. Consider the gear ratio you want – matching the existing ratio simplifies the process.
* Axle Shafts (Possibly): The axle shafts might need replacing depending on the condition of your existing ones and whether they're compatible with the new differential.
* New Bearings and Seals: These are essential for proper operation and longevity. Replacing these while you have the housing open is highly recommended.
* Gear Oil and Additive: The correct type and amount of gear oil are crucial. Consider using a friction modifier additive if recommended for your specific Posi-Traction unit.
* Necessary Tools: A variety of tools will be needed, including axle stands, jack, socket set, torque wrench (with the correct sockets for your axle), differential bearing installer/remover, and possibly a gear puller and installer.
2. Removal of the Existing Rear End:
* Safety First: Use jack stands to safely support the car. Never work under a car supported only by a jack.
* Disconnect Driveshaft: Separate the driveshaft from the differential.
* Remove Brake Lines and Shocks: Disconnect the brake lines and shocks from the rear axle housing.
* Remove U-bolts: Carefully remove the U-bolts that secure the rear axle to the leaf springs.
* Lower the Rear End: Slowly lower the rear end using the jack.
3. Installation of the Posi-Traction Differential:
* Disassembly (If Necessary): You may need to disassemble the old rear end to remove the existing differential. This involves removing the axle shafts, cover, and then the differential assembly.
* Installation of the New Differential: Carefully install the new posi-traction differential into the housing. Be mindful of proper bearing preload and shim adjustment. This step is the most technically challenging aspect and requires precision. Incorrectly installed bearings can lead to premature failure.
* Reassembly: Reassemble the rear end, ensuring everything is properly seated and torqued to specifications. This includes reinstalling the axles, bearings, seals, and cover. Follow instructions provided with the new differential if available, or consult a detailed repair manual.
* New Gear Oil: Fill the rear end with the correct type and amount of gear oil.
4. Reinstallation of the Rear End:
* Raise the Rear End: Carefully raise the rear end back into position.
* Reconnect U-bolts: Tighten the U-bolts to the correct torque specification.
* Reconnect Brake Lines and Shocks: Reconnect the brake lines and shocks.
* Reconnect Driveshaft: Reconnect the driveshaft.
* Test and Adjust: After reinstalling, test drive the vehicle carefully. Check for leaks, proper operation of the posi-traction, and unusual noises.
Important Considerations:
* Manual vs. Workshop Manual: A detailed shop manual for your 1965 Mustang is invaluable. It provides torque specifications, diagrams, and step-by-step instructions.
* Professional Help: This is a complex job. If you lack the necessary mechanical skills and tools, it's best to have a professional mechanic perform the installation. Improper installation can lead to serious damage or injury.
* Gear Ratio: Make sure the gear ratio of the Posi-Traction unit is compatible with your engine and driving style.
This process is a simplification. The specific steps and difficulties will vary depending on the condition of your existing rear end and the specific Posi-Traction unit you acquire. Always consult a repair manual and prioritize safety.
