1. Transmission and Transfer Case Compatibility:
* Transmission: While both trucks are F-150s, the exact transmission type (e.g., C6, E4OD) and bellhousing pattern from the 1987 donor need to be compatible with the 1989 engine. The 1989 engine's bellhousing bolt pattern might differ, requiring an adapter plate (if one exists) or a different transmission. You'll need to confirm this compatibility precisely.
* Transfer Case: If your 1989 truck is 4x4, you'll also need to check the transfer case compatibility. The 1987 transfer case might not bolt directly to the 1989 transmission.
* Torque Converter: The torque converter from the 1987 donor is essential and must be matched to the transmission.
2. Drive Shaft Lengths:
* The driveshaft lengths likely won't be correct. You'll almost certainly need to have custom driveshafts made or get them shortened/lengthened to accommodate the automatic transmission and transfer case (if applicable).
3. Wiring Harness and Electrical:
* Transmission Control Module (TCM): The automatic transmission will require a TCM (or PCM with integrated transmission control). The 1987 TCM might not be directly compatible with the 1989 wiring harness. You'll likely need to modify or replace a substantial portion of the wiring harness to accommodate the automatic transmission's electrical needs. This is highly complex and often requires significant electrical knowledge.
* Speed Sensor: The automatic transmission will have a different speed sensor signal compared to the manual transmission. You'll need to ensure the correct sensor is used and that the vehicle's computer can interpret its signal.
* Shift linkage: The shift linkage from the manual will be entirely unnecessary. You might need to fabricate mounts for the automatic transmission's shifter.
4. Pedal Assembly:
* You'll need to remove the clutch pedal assembly and install an automatic transmission pedal. This often involves modifying the firewall or using an aftermarket pedal assembly.
5. Cooling System:
* Automatic transmissions generally require a transmission cooler. Your 1989 F-150 might or might not already have one; if it doesn't, you'll need to install one.
6. Mechanical Components:
* Flywheel vs. Flexplate: The manual transmission uses a flywheel; the automatic uses a flexplate. The flexplate must be compatible with both the engine and the transmission.
* Crossmember: You might need to adapt or replace the crossmember to properly support the automatic transmission.
* Shifter: You'll need the shifter and linkage from the donor truck and potentially modify the floor or console to accommodate it.
7. Professional Assistance:
This conversion is a very advanced project. Unless you have extensive experience with automotive mechanics, electrical systems, and transmission work, it's highly recommended to seek professional assistance from a transmission specialist or a mechanic familiar with older F-Series trucks. The complexity and potential for errors make this a job best left to the experts.
In summary, while using parts from a similar-year vehicle helps, the differences between manual and automatic transmissions necessitate significant modifications. The cost of parts, labor, and potential unforeseen complications could easily outweigh the cost of simply finding a used 1989 F-150 with an automatic transmission.
