Alright so I’ve got a 98 f150 base model, 4.6 L, auto trans 4r70w, with a single core radiator. I was replacing the radiator when I broke a transmission cooler line, so naturally I ordered another one. I don’t have the special cooler lines that you need a special tool to remove, these are regular about 16mm fittings, male threaded lines. Anyways, so I broke the line that’s goes into the top radiator fitting, I believe the trans outlet to rad inlet. So, I ordered this part
https://www.oreillyauto.com/detail/c/dorman-oe-solutions/dorman-oe-solutions-transmission-oil-cooler-return-line/doe0/624226/v/a/5291/automotive-truck-1998-ford-f-150?q=Transmission+cooler+line

After struggling with it for a couple of days, I realized the fitting I was trying to thread into the transmission fitting was too big, and I checked the top side, same problem. The whole line is slightly bigger than what was there before. Can’t be sure if it’s been replaced before, though I did replace the transmission myself a few months back, and the old lines threaded in fine. I can’t seem to find any other part for this specific model, can anyone help?

 

Post photos
Ford made a few trans cooler line adapter fittings
New radiators generally come with a bag of adapter fittings
I think you got the wrong replacement line
Post photos is about the only way
Take photos of both line ends and the threads in the radiator