1967-1977 F250 4wd Super Duty axle and steering conversion

 

This conversion is to convert 1967-1977 F250 4wd trucks commonly known as highboys to 2005+ F250/F350 Super Duty front axles, coil spring suspension and 2005-2008 steering gear. These parts are CAD designed, laser cut, CNC bent, and fully welded with high quality equipment. These parts are designed so that they use factory drilled holes to locate each and every critical component. You won't need a tape measure! This takes a 9/10 difficulty 3 month job and makes it a 6/10 two weekend job. The axle does require a 2005+ steering box, neither a factory power assist or a 1978/79 box will work. The steering conversion requires a good amount of cutting and welding, otherwise the spring buckets and control arm brackets are mostly bolt in.

Step One: Remove factory components

 

Securely place the truck on jack stands and remove these parts:

-Front wheels

-Front brake hoses (the rubber portion)

-Front shicks

-All steering components

-Front driveline

-Front axle, leaf springs and shackles

-Front upper shock mount bracket

-Brake line support bracket on outside of frame

-Rubber bump stop. There is an opening on the inside of the frame to get a ratchet and socket in there, but chances are you will need to cut this off. A sawzall and a good metal blade will get the job done,

-4 horizontal engine perch bolts per side (don't worry the engine won't fall because there are two vertical bolts per side that stay in place)

Clean the front outer frame rails with an angle grinder and wire wheel and spray it with a coat of paint. A thick layer of undercoating may prevent the spring buckets from seating correctly so this is important.

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Step Two: Install front spring buckets

These bolt in and are fairly self explanatory but follow these steps:

-Place spring buckets on frame, be careful not to damage factory brake lines

-Start all 7/16" X 5" horizontal bolts/nuts but do not tighten yet, except do not start the two front driver side bolts yet, leave these out for now

-Install axle bump stops and fully tighten. These have the effect of pressing the bucket up close against the frame. I am using part number C5TZ-3020-A for a factory style bump stop. You can go aftermarket but be sure to get the style with one bolt in the center

-Tighten horizontal bolts (still excluding two front driver side bolts). I torqued to 40 ft/lbs and this seems to work well. The frame is boxed in here and over tightening these bolts may lead to the frame being crushed,

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Step Three: Install track bar bracket

 

On driver side outer frame rail, just behind original factory steering box location, grind factory locating tabs off. These are not structural, just used by the factory to set the parts together for welding.

Cut factory cross member on driver side as pictured. I previously cut and welded plates for 78/79 steering in this frame.

The track bar bracket bracket is designed to be bolted in similar to how it is on a Super Duty. Start by bolting on this plate that goes on the outside of the frame. it shares two bolt holes with the spring bucket and one with the steering box. these two spring bucket bolt holes help locate the bracket without measuring. This piece also locates a new crossmember part that will be welded in.

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Cut factory crossmember as pictured

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Next the track bar bracket will be bolted to the frame

 

Use the two forward spring bucket brackets to attach the track bar bracket. just snug, not tight yet

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Make sure the bracket is seated flush against the frame, then use a 7/16" drill bit to drill for the two holes indicated below. Install 7/16" X 1.5" Bolts in each of these holes with flange lock nut on inside. Weld the nuts to the inside of the frame. Be very careful not to damage the thread and do not use impact on these.

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For the next step you will need the below pictured rectagle plate with two bolt holes, two 1/2" X 1.5" bolts and two 1/2" flange nuts.

Tighten the bolts and nuts over the flat plate and weld the flange nuts to the plate. Remove the bolts.

With the track bar bracket bolted to the frame with the 4 horizontal bolts and seated flush against the frame vertically and horizontally, bolt the rectangle bracket to the top of the track bar as pictured. You may need to use a grinder to cut the rectangle bracket, or trim your frame up more or both.

The flat bracket will be welded to your frame and crossmember and becomes the new lower section of your crossmember. Note that the track bar bracket itself is NOT welded to your frame and for this steps acts only as a tool to locate the rectangle bracket.

You may want to remove the track bar bracket from the crossmember to complete the welding. For now, weld only the three sides of this rectangle bracket and don't weld in any of the other pieces.

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Below shows how the rectangle plate mounts above the track bar bracket. This rectangle plate becomes part of the crossmember

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I don't have a great picture of this part but above is the finished product and below is the track bar bracket without the flat plate welded in place. Ignore the steering plate in that picture- dont put that in yet

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Next get these two track bar plates and the track bolt you hopefully have from the Super Duty, Use a 30mm wocket and wrench to tighten to the track bar. Place flush up against the track bar bracket and tack in place very thoroughly with a welder.

Before you tack in place, Double check that the two pieces are centered over the vertical and horizontal bolts. This is very important as welding these off center will make it impossible to get a socket in there.

Remove and fully weld. Take your time- it shouldn't warp as this is thick steel but still don't let it get to hot.

Paint it and reattach to frame.

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Note: Per my testing this location for the track bar bracket lets you use a 2005 Super Duty track bar and centers the axle very well under the highboy frame. If for some reason the axle is off of center, you will need an adjustable track bar but these are commonly available through other vendors.

Step Four: Steering

 

Bolt steering plate against outside of frame using three 7/16" bolts and nuts. Now use the plate combined with the pictured step spacers as a template to drill the two new holes in the frame. Use a 9/16" drill bit. You'll notice that these steps have some overlap with the track bar bracket installation.

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Picture above shows how the new plate is temporarily bolted to the frame using the 3 original bolt holds that held on the manual steering box.

Steering box plate spacers

This step is important and easy to do incorrectly so take your time and double check before you weld!

Weld spacers as pictured. This plate is not symmetrical so double check which side you are welding on!

Position the plate on your welding table as pictured

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There are three spacers that have stepped outside diameters. Two are longer and one is shorter. Insert them into the correct side of the steering box plate as pictured with the small one going into the top of the plate.

The picture below shows the spacers NOT fully installed for the same of showing which one goes where. The spacers slide all the way into the plate until they bottom out, then they are welded.

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Below are two pictures of the finished product front and back

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Before you get any further, double check that the M14 bolts do in fact thread through the plate and into the steering box. the picture below shows an earlier prototype of the steering box plate, but the idea is the same. if there are bolt fitment issues, address them now

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Next install the steering box plate on the inside of your frame as pictured below. Use a combination of the two new M14 x 120mm bolts and matching m14 nuts (these nuts are only for the purpose of this mock up) and one 7/16 x 3" bolt, the 2" steel spacer, and 7/16 nut in the lower front corner of the steering plate to locate this plate. No need to cinch it down tight, just getting it ready to weld. Yes you can potentially install all three 7/16 bolts in the factory drilled locations but I found that the other two did not provide any benefit to locating the plate.

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2" long spacer back here for mock up

I didn't have the right size bolts so I used these spacers that are sticking out.

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Use the two other flat plates to box in the other sides and weld er up! Don't begin welding until you have test fit all three flat plates. You may need to trim these pieces, but only slightly. for my installation, I only trimmed the rectangle as you can see below.

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Steering arm bar

A standard (not dropped) pitman arm works well with factory height SD front coil springs. You will not be able to use a Super Duty steering bar because the distance from box to passenger side axle tie rod end is smaller. The kit I make includes a tie rod end for the pitman arm and rod ends specially machined for this application. You will need to separately source a 1.5" OD 1.0" ID steel dom tube. Part number TU1031 from summit racing works great and is what I have here. Double check before cutting but I found that cutting the steel tube to 28 1/8" worked great. Install the tube ends- and you may need to gently tap them to slide in- then fully weld them both in place.

Install the included jam nuts on either tie rod end before installing this steering bar

The pitman arm nut requires a 46mm socket.

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Step Four: Install radius arm brackets

 

These radius arm brackets use 4 factory drilled holes. 3 holes are the transmission cross member support and one is a large unused hole just behind these three.

Do one side at a time, you don't want both sides of the transmission crossmember loose at the same time.

Support the transmission in the middle of the transmission crossmember. Don't press too hard up against this, it weighs a lot less than an engine. Cut the three rivets and pound these out. I find it helpful to remove one rivet and temporarily install a 1/2" bolt and nut so that the bracket stays securely in place while you pound out the other rivets. Ream out the holes with a 1/2" drill bit as needed.

Install the radius arm brackets. Start all bolts before tightening any. Double check that the bracket is pushed upward tight against the frame both the horizontal and vertical surfaces before tightening the horizontal bolts, then tighten those bolts.

Drill out 3 vertical holes using the holes on the radius arm brackets as a guide. Remove the brackets again to make sure no metal shavings are stuck between the brackets and the frame, then reinstall. 

On the forward vertical bolt, you will notice that the frame has a slight bend to it to that does not let the bracket sit flush with the frame. Use a 1/2" washer in here to fill the gap- otherwise the bolt here will place a lot of stress on the frame.

Torque all 1/2" bolts to 60 ft/lbs.

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Other Tips and Info

 

Shock Absorbers

The shocks will match the springs. If you are using a 2005 F350 front axle/spring, then get a shock for that same application. If you have lift springs, then get shocks for a lifted Super Duty.

Brake Booster/ Master

Most factory brake systems will not put out enough brake fluid volume to feed the large Super Duty calipers. Your brake pedal will feel squishy and be hitting the floor even when the brakes are properly bled. I recommend upgrading to a Super Duty booster and master at the same time you do this swap. Those systems come with a 1 3/8" bore master that puts out plenty of fluid.

Lift

This kit will have the effect of lifting your highboy about 2". If you want more, it will accept a Super Duty lift. a 3" SD lift will equal about a 6" highboy lift.

Front Brake Lines

Use Super Duty rubber flexible hoses. These new spring buckets have provisions for securing the rubber hose's tab to the bucket. Then a piece of 3/16" brake line can be used to plumb the rubber SD hose into your factory brake line.

Rear Axle

A sterling 10.5 works great and will match your new front axle. You will need to cut and weld new perches, get new U bolts, maybe a new top plate, etc. The parking brake of a sterling can be rigged up to the front section of your highboy parking brake cable. You will want to upgrade your rear driveline to a larger diameter shaft with 1410 joints if you haven't already

Front Driveline

The 2005 SD axle I used for the swap in these pictures accepted a common 1350 U joint. You can either get a conversion U joint to make your original driveline work or you can get a 1350 yoke for your NP205 transfer case and upgrade to a new higher quality driveline meant for 1350 joints. 1350's and a new driveline are really the way to go if you have the budget.

Sway bars

I am working on this but it looks like the best rear sway bar option is a Ford Ranger sway bar, and the front SD sway bar should be able to be fashioned to the highboy frame easy enough. More info to come!

Steering Shaft

The 05-08 SD steering box has a 3/4" 36 spline shaft, an extremely common connection. I was able to 100% reuse my steering shaft that I had with the 78/79 F250 4wd steering conversion prior to this SD steering conversion

Alignment

Have the alignment shop align the vehicle as if they were aligning the Super Duty donor vehicle, not your highboy

Death Wobble ?

Super Duty trucks have been plagued with death wobble issues and the fix is simple. These parts wear out and now is a great time to replace them if your donor vehicle had high miles or unknown miles- track bar ball joint, track bar bushing, tie rod ends, and ball joints. Rockauto has good prices. You will get it aligned anyways so bite the bullet and do it now!

Wheels and Tires

The Super Duty axles are wider so to keep a factory-like track width, you will want wheels that have a larger backspacing. A minimum of 17" wheel size is required to clear the brakes. I measured the overall tread width on the original super duty wheels/tires and compared them to my original highboy axles/wheels and 33" tires and it was within an inch of the same. The 33" tires are a good amount wider than a skinny factory tire though. I ended up going with a 17X9 wheel with 5.71" backspacing- the part number is KMC XD82979087918. The tires I used were Yokohama Geolandar LT285/70R17, part number 110133320. These work great with factory height SD springs, right great, look great, and have great traction. With this wheel/tire combo I gained only 1/2" of overall tire width from my original highboy axles/wheels/285/75r16 tires.