New build input
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5th Wheeling
Joined: Aug 2011
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New build input
I currently own a 78 2wd F150 and I am about to do a drive train swap from a 1990 F150 into my 78.
I found a pretty decent Highboy and have always wanted another Highboy. My question is do you think if I re-geared the Highboy would 15 mpg with an updated drivetrain be achieved? It would be nice to sometimes have the 4x4 capability. I don't think 15 mpg is unachievable in the 2wd 78. Thanks Anthony
I found a pretty decent Highboy and have always wanted another Highboy. My question is do you think if I re-geared the Highboy would 15 mpg with an updated drivetrain be achieved? It would be nice to sometimes have the 4x4 capability. I don't think 15 mpg is unachievable in the 2wd 78. Thanks Anthony
Lead Driver
Joined: Oct 2018
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This has been discussed quite a bit and the consensus seems to be it's cheaper and easier to just buy a 4x4. I agree. if you're going to convert to 4wd you need to buy a junk one for parts so why not buy a little better junk one and use the parts off the 2wd you have to fix it. or just buy a 4wd and sell your 2wd makes more sense.
A 15 mpg high boy isn't impossible but considering it's hard to get over 15 with a new 3/4 ton 4wd it's not going to be easy. and I'd bet money a 1990 drive train isn't going to do it since it didn't in 1990.
A 15 mpg high boy isn't impossible but considering it's hard to get over 15 with a new 3/4 ton 4wd it's not going to be easy. and I'd bet money a 1990 drive train isn't going to do it since it didn't in 1990.
Laughing Gas
Joined: Feb 2011
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You'll never see 15 with a highboy IMO. Pushing too much rolling mass and weight down the road. If you did manage to achieve 15 mpg, it would have cost you so much money to get there that you would never get any payback even at $4.20/gal.
Fuel mileage is typically very low on the priority list of folks looking for or driving a highboy.
Fuel mileage is typically very low on the priority list of folks looking for or driving a highboy.
Moderator & parts slinger
Joined: Feb 2007
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From: S/W Missouri, Polk county
440 and Mark are 100% correct with their answers. But if you want the long version answer to a 4wd conversion from FTE archives."There is nothing nuts and bolts about a 4wd conversion, there is not a thing that is bolt on or swappable. The engine cross members are entirely different, and this means that if an un molested truck is what you are after, it will be impossible to create one with a 2wd platform.
The 2wd will have to be lifted quite a way to clear the front diff. 2wd trucks are coil sprung and most F250 4wd's are leaf sprung. None of the suspension items are even close to the same, so you will be fabricating or modifying some original 4wd stuff to work.
Steering systems are entirely different as well, so you will be upgrading that too. My last conversion with leaf's ran me several thousand dollars, and that was with the work that I performed for free. The difference in sale values between a 4wd and 2wd are minimal, and the 4wd conversion is hardly justifiable.
Well the frames are similar, with a few exceptions. The frame horns are slightly different, and the frame widths aft of the cab are different from 73 to 77 trucks. The frame rise is also slightly different, but this is not a show stopper and does not make much difference one the fabrication begins.
Now the important question is whether or not you will be using a coils springs or a leaf spring. It is possible to install a 78/9 radius arm and suspension. Not a big deal really, and with a standard cab this is reasonable. Not quite as easy with a super cab and or crew cab.
The 2wd frames are not cut for the shackle pivot, and they do not have the provisions for a spring hanger, but again, this is not a deal breaker. Installing a pivot is just a tedious process, accuracy is key.
Ok, so next is the transfer case. You have two choices, install a married case, and this requires the proper transmission. Might find some difficulty making or modifying an output shaft to accommodate the early C6 and a married transfer case. So then the next option is to find a divorced transfer case, and install this. You will have to make up a cross member, but then you will have to get creative with the shifter linkage. See the 4wd trans will have an adapter or tailshaft with a pivot for a typical 205 shifter. Fabrication is the only limiting factor here.
Next and final factor will be the speedo. See your speedo works from the trans, so that being the case, you will have to get a speed reference from the t-case. If you do not, the speedo will read twice as fast when you put the case in low range. But you will be in 4 low so who cares how fast you are going.
As mentioned the steering box will have to be relocated, and the truck will require some lift. That engine crossmember has limited clearance so you will be looking at some lift to even clear it. The other option would be to remove it and replace it with a tubular unit."
The 2wd will have to be lifted quite a way to clear the front diff. 2wd trucks are coil sprung and most F250 4wd's are leaf sprung. None of the suspension items are even close to the same, so you will be fabricating or modifying some original 4wd stuff to work.
Steering systems are entirely different as well, so you will be upgrading that too. My last conversion with leaf's ran me several thousand dollars, and that was with the work that I performed for free. The difference in sale values between a 4wd and 2wd are minimal, and the 4wd conversion is hardly justifiable.
Well the frames are similar, with a few exceptions. The frame horns are slightly different, and the frame widths aft of the cab are different from 73 to 77 trucks. The frame rise is also slightly different, but this is not a show stopper and does not make much difference one the fabrication begins.
Now the important question is whether or not you will be using a coils springs or a leaf spring. It is possible to install a 78/9 radius arm and suspension. Not a big deal really, and with a standard cab this is reasonable. Not quite as easy with a super cab and or crew cab.
The 2wd frames are not cut for the shackle pivot, and they do not have the provisions for a spring hanger, but again, this is not a deal breaker. Installing a pivot is just a tedious process, accuracy is key.
Ok, so next is the transfer case. You have two choices, install a married case, and this requires the proper transmission. Might find some difficulty making or modifying an output shaft to accommodate the early C6 and a married transfer case. So then the next option is to find a divorced transfer case, and install this. You will have to make up a cross member, but then you will have to get creative with the shifter linkage. See the 4wd trans will have an adapter or tailshaft with a pivot for a typical 205 shifter. Fabrication is the only limiting factor here.
Next and final factor will be the speedo. See your speedo works from the trans, so that being the case, you will have to get a speed reference from the t-case. If you do not, the speedo will read twice as fast when you put the case in low range. But you will be in 4 low so who cares how fast you are going.
As mentioned the steering box will have to be relocated, and the truck will require some lift. That engine crossmember has limited clearance so you will be looking at some lift to even clear it. The other option would be to remove it and replace it with a tubular unit."
Lead Driver
Joined: Oct 2018
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If you're looking for a low cost way to get into a 4wd I'd buy something like this. use the rig you have for parts or sell it.
1978 ford f250 camper special 4x4 - cars & trucks - by owner -... (craigslist.org)
1978 ford f250 camper special 4x4 - cars & trucks - by owner -... (craigslist.org)
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