Originally Posted by Mark Kovalsky

Every 4R100 has the same gear ratios. There are differences, however. There are different 4R100s for 5.4L, 6.8L, and 7.3L. You need to get one from the same engine that's in your E-350. Also, if your E-350 has a parking brake on the back of the trans, you'll need a 4x4 transmission. Most likely you don't have the parking brake, so you'd need one from a 4x2.

Originally Posted by Panichappens

I'm not sure about the e350 but my 99 e450 has a parking break "drum" or "bell housing" (I'm not sure what it's called) and that was the big difference to me when I was scouting for a used tranny.. the F series didn't have that.. to my knowledge but I'm not a mechanic. I have had trouble figuring out my replacement also. I bought an 04 4r100 with high hopes cause they look identical but once installed it falls on it's face in 1st gear.. it will go into gear in limp mode tho. I need to know how to switch out the electrical components or if a Ford computer tune would do it... So, if you find out more info.. please share it
Thanks