However, here's a general overview of the steps involved. This is NOT a comprehensive guide, and variations exist depending on the specific year and model of your D21. Always refer to a factory service manual for your specific vehicle.
Tools you'll likely need:
* Jack and jack stands: Securely support the truck. Safety is paramount.
* Transmission jack: Essential for safely supporting the transmission during removal.
* Socket set and wrenches: Various sizes will be needed for bolts and nuts.
* Torque wrench: Crucial for properly tightening bolts to prevent damage.
* Pry bar (carefully used): May be needed to break loose stubborn components.
* Drain pan: For transmission fluid.
* Shop rags: For cleaning.
* Penetrating oil: To help loosen rusted or seized bolts.
* Factory service manual: Absolutely essential for detailed instructions and torque specifications.
General Steps (In Simplified Form):
1. Safety First: Disconnect the negative battery terminal. Support the vehicle securely on jack stands.
2. Drain Transmission Fluid: Locate the transmission drain plug and drain the fluid into a suitable container.
3. Disconnect Components:
* Driveshaft: Disconnect the driveshaft(s) from the transmission.
* Shift linkage: Disconnect the shift linkage from the transmission.
* Clutch cable (if applicable): Disconnect the clutch cable.
* Speedometer cable: Disconnect the speedometer cable.
* Wiring harness: Disconnect any electrical connectors attached to the transmission.
* Exhaust system (potentially): Some parts of the exhaust may need to be loosened or removed to provide clearance.
4. Remove the Transmission Crossmember: This will support the transmission. You'll likely need to unbolt it from the frame.
5. Separate the Transmission from the Engine: This is the most challenging part. This involves removing the bellhousing bolts connecting the transmission to the engine. You may need to use a pry bar carefully to help separate the transmission and engine, but be extremely cautious not to damage anything.
6. Lower the Transmission: Using the transmission jack, carefully lower the transmission from the engine bay.
7. Clean the mating surfaces: Before reinstalling, clean both the engine and transmission mating surfaces thoroughly.
Important Considerations:
* Clutch: You'll likely need to replace the clutch while you have the transmission out, as it's a good opportunity to do so. This adds significant complexity.
* Pilot bearing: The pilot bearing on the input shaft of the transmission may also need replacing.
* Torque Specifications: Incorrect torque can severely damage parts. Use your service manual to ensure you tighten everything to the correct specification.
* Alignment: Proper alignment of the transmission to the engine is critical upon reinstallation.
This is a condensed overview. The actual process is far more complex and involves many more detailed steps. Again, I strongly urge you to consult a factory service manual for your specific Nissan D21 and ideally, have a qualified mechanic perform this repair. Attempting this without proper experience and tools can lead to significant damage to your vehicle.
