How hard would it be to convert a 2 wheel drive f150 into a 4 wheel drive? the year of the truck is 78.

 

i would not suggest it,

it involves splicing the frame,

basically ask your self some questions, how good a welder are you? have you modified a frame before?

finding a 4x4 frame is much easier and safer,

thus i don't recommend converting a 4x2 frame to 4x4,

-Brent

 

Agree, not worth it. Your best bet is just buy a different truck.
My cousin did put the front axle from a 1977 F-150 in his 1989 F-150. The 89 4x4 has the TTB in the front which is similar to the front suspension you have in your 2wd. You know that "pan" that goes under your engine, it's part of the frame? The 89 4x4 has that too. Even with a big lift he had to trim that out and re-brace the frame, you would have to do the same, a 1978 4x4 does not have that pan at all but it is structural on a 2wd. Then you have to mount a transfer case, he didn't have to do that. What he did was a pretty big job, I was there for a lot of it. He said it was worth it and I agree. I hate that TTB. (I owned an 80 and a 93 Bronco). His new articulation is amazing compared to what he had. In has case it was less work than what you are looking at and there was no 1989 F-150 solid axle he could just go out and buy. In your case you can just go buy a 1978 4x4. I only paid $700 for my truck it was in pretty nice shape for the age but the 351m was tired, thats for sure. There are a few pics (not that great) in my gallery if you want to see it. Its being prepped for paint right now. After the 460 and body work I have a lot more than $700 in it but it could have been usable for under $1000 and like I said the body was pretty solid.

 

Not all conversions require a spliced frame. As a matter of fact the 1/2 ton os probably the best candidate for a conversion. Imagine for a moment the actual suspension differences between the 2wd and 4wd 1/2 ton. Not much of a difference really.
Purchase a lift kit for the 78/9 F150 / Bronco with long radius arms and use some stock coil buckets for the same vehicle, and the suspension is done. This will require a lift kit of 6 inches or better. This is required to clear the 2wd crossmember.
The difficult part is what to do with the transfer case and x-members. Not a deal breaker, but can be a task. A 2wd trans will have to be taken apart to replace the tailshaft. Of course driveshafts will have to be purchased, and then you get to the steering. 2wd trucks steer from behind the axle and 4wd's locate the steering box forward of the axle. Install the appropriate steering box and things are starting to come together.
Crossmember clearance is only an issue of you want to keep the ride heigth down. Notice the low hanging x-member here:



This is a ton of work, so dont be tricked into thinking this is a simple task. Most that attempt this never get it complete.

Consider all of the parts that you need to accomplish this task and add up all of the costs associated, and you will probably find that it is a far better choice to find a 4wd to begin with. As little as I have seen 4wd trucks, I have found that it is simply not worth the effort to convert one, though I have converted several.

 

ya you can do it that way, its not a easy route either,

in the end i would suggest someone go find a 4x4 truck, or a 4x4 frame,

i found a '77 short box F-150 4x4 frame, and simply swapped everything i could over, and of course my AOD had to be modified by having its tail shaft swapped out for a longer one, since the longer shaft has to go into the transfer case

-Brent

 

Yeah after talking to my freind whos big in 4x4 trucks its not gona be worth it for me to do it. i dont have loads of cash to throw at this thing. so ill stick with 2wheel drive and find something else to do with this truck. mabey stock height and a little lower in the front with a big engine. Its going to be a while before i figure out exactly what im going to do.