Q: I'm not asking about the engine now. But would i be able to use the transmission from a 2000 ford f150 4.2 liter engine in a 2004

The only transmission interchange that might work for the 2005 Explorer with the 4.0L engine is the 2004 Explorer but even that depends on whether you have the 2WD or 4WD version of the Explorer. The F150 transmission from 2000 will definitely not work as it is both mechanically and electrically incompatible with that used in 2005.

If you are looking for a transmission for your 2005 Explorer, visit Car-Part.com and you will find an exact match for your car (there are many listed). Transmission swaps on modern computer controlled vehicles must be exact matches because if you attempt to use a transmission that is not cataloged as a direct cross reference, you will find that the engine and transmission computers are not interchangeable. Consequently, even if you can get a "different" transmission to physically fit, it will not operate properly and the PCM will spit out error codes. If you are interested in a transmission replacement (OEM to OEM), YourMechanic professionals in certain locales can assist with that. Please simply inquire based on your locale. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.