So I got a good deal on a 99 4x4 6 speed 7.3 but the 4x4 didn't work. After some diagnostics I decided not to even bother trying to fix a problematic system and go manual. I looked at swapping t case but that is just expensive and really pretty time consuming so I started looking at converting. Tried to find info online pretty sparse. So I took apart the motor and gears and looked how it all worked. Then by chance I looked under my father in laws 1991 ford with a zf5 and the linkages looked like they might bolt up. Since the truck and trans is completely trash I took the linkage out and it bolted straight on couldn't believe the luck. I then pulled up the carpet and undid the plate under the carpet. BTW the glue on this is awesome after pounding and prying I finally got out a small torch heated it up and it came right off.The linkage looked like it should so I cut the carpet and put it about where it should go. I took the little cam deal with the gear that goes on the t case shifter sticking out of the case and welded on a piece of steel with a hole where i figured it should go. I stuck a bolt off that and measured roughly from the bolt to mid way on the 91s shift linkage. I cut another piece of steel that length and welded them together. I reinstalled and held it up circling the bolt with a pen so I could drill the hole for the linkage. I installed the linkage made a rubber bushing for the bolt out of some hose and tested it finally I had four wheel drive. Now to hold all that on I used the outside of the shift motor case since the inside can't go on because of the new arm and the gear is flipped. I cut the top to fit where the arm sticks out and chopped some of the bottom off to let it drain. I used some washers as spacers to make up for the inner half and there I have 4x4. I still haven't figured if the shift boot out of the 91 will work it's kind of hammered but I will let you know in the next day or two. This took me a morning of figuring it out with basic tools and welding working in the gravel so it should be doable for most.

I know I'm definitely not a writer so any questions just message me or comment.

 

So with some carpet trimming the 91 shifter housing all fit too. Someone call ford and tell them they made something that interchanges so they can recall it. all out of a 91 ford 460 zf5 f350