1. PCM Compatibility: This is the biggest challenge. Your 1999 Chevy's PCM needs to be able to communicate with and control the 4L80E. Here are your options:
* Replacement PCM: The most reliable solution is to source a PCM from a vehicle that originally came with a 4L80E. This PCM will be pre-programmed with the correct transmission control strategies. You'll need to find one compatible with your year, engine, and other vehicle options. This will often require finding a PCM from a truck or SUV and may involve matching VIN numbers or using a professional reprogramming service.
* Reprogramming/Tuning: A professional tuner can reprogram your existing PCM to support the 4L80E. This requires specialized equipment and knowledge. They'll need to adjust parameters like shift points, torque converter lockup, and various sensor inputs to work correctly with the new transmission. This is often the preferred method for performance tuning but can be expensive.
2. Wiring Harness: The wiring harness for the 4L80E is different than the one for your original transmission. You'll need to:
* Identify Wiring Differences: Carefully compare the wiring diagrams for both transmissions.
* Adapt the Harness: You'll likely need to either modify your existing harness or create a custom harness to connect the 4L80E to the PCM. This is a complex task that requires considerable electrical knowledge.
* Add Necessary Sensors and Solenoids: The 4L80E uses different sensors and solenoids than your original transmission. Ensure these are properly installed and connected.
3. Torque Converter and Flexplate: Ensure compatibility between the 4L80E torque converter and your engine's flexplate. An incorrect combination can lead to catastrophic engine or transmission failure.
4. Transmission Cooler: The 4L80E generates more heat than many other automatic transmissions. You will likely need a larger transmission cooler than the one that was originally installed.
5. Mechanical Aspects: This isn't directly computer-related, but crucial:
* Transmission Mount: You may need a new transmission mount to properly support the 4L80E.
* Driveshaft: The driveshaft length may need to be adjusted to accommodate the 4L80E's different output shaft length.
* Shift Linkage/Cable: You'll need to adapt the shift linkage or cable to work with the 4L80E.
In Summary: This is a complex undertaking requiring significant mechanical and electrical knowledge. Unless you have experience with automotive electrical systems, PCM programming, and transmission swaps, it's strongly recommended to seek professional help from a qualified transmission shop or automotive electrician. Attempting this without proper knowledge could lead to significant damage to your vehicle. Start by finding a reputable shop and discussing your project with them; they can provide a more accurate assessment of the work involved and cost.
