As stated in previous thread, I am having transmission problems with my 02 F 150 Lariat 5.4 liter. I determined the transmission was definitely bad. I have decided to change it myself for the experience. The shop it was at told me I had a 4r100 trans. So i got a good deal on one and dropped the trans. out of my truck to find out it was smaller and is the 4r70w. My question is how hard would it be to use the more heavy duty 4r100 that I already have. Or should i sell that one and get the 4r70w that originally came in the truck.