Technical Articles

RC Dana 60 Coil-Sprung Front Axle Conversion

-- by James Oxley (revised 7/4/01)


Tired of breaking D44 front U-joints or bending the front axle tube after 6 foot air jumps? Well, here is the solution. Install a D60 front.


Let me say up front that is will be a pretty spendy adventure and for 99% of us, at least some machine shop work will be needed.

So lets get to it!!!!!!


First you need to locate a 78/79 RC D60 front. They are getting harder and harder to find. I paid $600.00 for mine, but I doubt you will get it that cheap. In some parts of the country they go for $1200.00+. You can not "easily" use an 86-97, D60 front with C-bush mounts. In 1980, Ford changed the front of frame on all F-series (widened), they also moved the differential outboard, not leaving enough space for the C-bush mount on the drivers side.


Next you will need to decide if you are going to hack up your stock axle or look for a donor D44 front for the C-bushing mounts. This was an easy decision for me as I had one with a bent front tube from doing 30+ jumps and NO suspension lift :-)


(Note, when looking for donor front axle, make sure you get one with same size tube as your bronco axle, some F100's had light duty D44 front, which will bolt into any C-bushing front end, but the tube is smaller and the mounts are lighter duty).


Make sure truck is level, side to side and front to back. Measure the pinion angle of your currently installed diff. Now measure the angle of both your radius arms (hopefully they are the same or at least close). Then, take your donor axle, gut it and find a machine shop. Both C-bush mounts need to have the tube cut off of each side. Then each mount must be bored out to a D60 front axle tube size, which is a hair over 3". After boring, mount is cut in half. Place each half against D60 front and install D60 front in suspension with springs, leaving C-bush cap bolts slightly loose. Drivers side mount just about fits and should look like this after final welding. (See Figures 1, and 2). Passenger side mount will look like this when done. Also note massive 1410 axle U-joint :-) (see figure 3).


Leave front shocks off at this point if you have quads. Make sure truck is level again and measure radius arm angles. They should be the same as before and if not figure out why. You may have one spring longer than the other, lower spring mount may be bent on one side (obviously, this should have shown itself on previous measurements), or one C-bush mount may be binding causing one spring to  compress slightly. Now rotate axle until pinion is at the angle that you initially measured. Now is the time to decide if you want to rotate pinion to something other than stock angle. More castor means rotating pinion downward, but that also means a worse pinion angle. You can adjust castor either way later on up to 7 degrees with bushings, so it is usually best to set pinion angle at stock location Tack weld in several spots and disassemble front suspension. Check to make sure C-bush mounts are rotated the same angle in relation to each other. Again they should be fairly close. If not, you may have something wrong in the front suspension.


Weld up the mounts all the way around on ends and between each half of each mount where they were cut in half. Have a PRO do this unless you weld for a living (it's not worth your life for $100.00 of welding!!!!!!!!!!!!!). After welding install axle and bolt up passenger tie rod end. Adjust drivers tie rod end until you can reach drivers side knuckle. It will take quite a bit of "unscrewing" to get it to reach.


After getting toe more or less aligned, attempt to install front shocks. Fairly heavy grinding of shock brackets and/or forward part of C-bush cap may have to be done to keep tie rod end from hitting these mounts. If you have thinner tires, the limit of steering may be tie rod end hitting these shock brackets and/or front C-bush metal cap. Adjust steering stops (might need to make new one's from 1/2 inch bolts) until tie rods do not hit anything at full lock. A substantial limit in steering may be required with really wide tires. Luckily, a D44HD 8 lug or D60 front is wider (over stock D44 front axle) by a little over an inch, this helps with radius arm rubbing.


I also made custom adj. drag link (See Figure 4) using a tie rod end setup (have this PROFESSIONALLY welded if you do it!!!!!!!!!) and used a Superlift adjustable track bar. Front drive shaft will need to be shortened and U-joint at pinion changed to a 1330 joint if you have a 78 bronc (79's had 1330's stock).


Other than that, it is pretty much a bolt in. Track bar may hit tie rods, front diff cover and/or drag link at full suspension "stuff" of drivers front tire if you have little or no lift. When you're done you can hammer it through mud holes like this and your front end won't even whimper :-).



Notes for Converting to F250/F350 Leaf-Sprung Axle 


Another alternative to converting a Bronco to a D60 coil spring setup would be to use a D60 leaf spring setup such as the type used in the F-250 and F-350 leaf spring axles. Unfortunately, this type of conversion is much easier said than done. The F250/350 had a different frame than F150/Bronco. The Power Steering box mounts inside the frame on the F250/350 chassis vs. outside the frame on F150/Bronco chassis. A minimum of 8" of lift would be needed if you use a 1/2 ton PS box/pitman arm and leaf spring suspension. The problem is the pitman arm sits directly under frame, right where leaf sits. When the suspension is flexed up, the leaf will hit the pitman arm (actually hit draglink end joint first). Hence a very high lift will be needed to do this. In addition, there are many advantages to using a coil spring setup vs a leaf spring setup, such as:

  1. A coil setup will hold up to weight of 60 front and 44" boggers (tested by me :-)),

  2. Coils usually flex better.

  3. Coils ride 1000 times better than leaf. Even with 200 lb (each) tires, my bronc is not horrible riding with Superlifts 9" springs (which is one of the softest, non-custom made spring available).

I do think a leaf spring suspension is tougher overall if you do high speed desert pre-running type stuff, but then you would be getting lots of air and the clearance issue between drag link and leaf spring would be even more of a factor. I've heard of some people chopping off the front end of a F250 frame and welding it to a bronco frame (to use F250 steering box). You can also just chop out and swap in the first cross member which is really the big difference between the two of them.




*** Disclaimer ***


All vehicle modifications listed in this article and most other articles appearing in ProjectBronco.COM are for off-road use only and on vehicles that are not driven on the street.  Any modifications made to a passenger car vehicle or light-duty truck should only be performed by a certified mechanic and approved for use by the Original Equipment Manufacture (OEM) of the vehicle.