Hey guys I'm new to this, I have a 1999 Ford Expedition with the 5.4, and I might be needing a new transmission, I have the 4r100 but I don't know if mine is the XL1P-DB OR THE XL3P-HP, How do I find this out?? thanks

 

There should be a trans code on the door or pillar sticker showing the trans code. That will tell you what was installed at the time your vehicle was built..

 

There should be a white build/data plate attached to the side of the trans case.