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ultimate F 150 Part 4 - dynatrac Housing - Photo 33806680

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  • The ProRock 60 housing from Dynatrac is designed for maximum ground clearance when used as a solid axle; however, we wanted extreme clearance along the top of the casting to clear the engine oil pan. This was achieved by taking an old housing and chopping away at it until it fit nicely beside the engine. Dynatrac took this mockup and machined a new axlehousing to match the chiseled one to fit in the F-150.
The ProRock 60 housing from Dynatrac is designed for maximum ground clearance when used as a solid axle; however, we wanted extreme clearance along the top of the casting to clear the engine oil pan. This was achieved by taking an old housing and chopping away at it until it fit nicely beside the engine. Dynatrac took this mockup and machined a new axlehousing to match the chiseled one to fit in the F-150.
Above all that aluminum skidplating and plastic cladding on our EcoBoost F-150 is the infamous independent front suspension (IFS). IFS has good ride characteristics, but when modified for large tires the many adjustable mounting points can loosen and cause added tire wear and steering woes. Add to that the lack of gearing and locker options and the fact that most half-ton axle CVs are not up to the stress of big tires, and you can see our qualms with the average IFS. The Ford IFS isn’t bad; in fact, it does its intended job just fine. We just want to complicate its job with larger tires, lower gears, locking differentials, and hitting bigger obstacles off-road than it was designed for. With these considerations, we pulled the aluminum housing and halfshafts out for upgraded replacements as well as the A-arms, EPAS (electric power assisted steering), and front bumper. Our F-150 has 420 lb-ft of torque from the EcoBoost, six-speed automatic transmission with a 4.17:1 First gear, and a Borg Warner 44-19 transfer case with a low range of 2.64:1. We didn’t find any aftermarket transfer cases that would adapt to our six-speed, so we opted to upgrade our axle ratios to as low as possible, resulting in a 5.38:1 ring-and-pinion ratio. This should give us a crawl ratio of around 60:1, about average for this much truck and tire. Our plan for the IFS was simple enough: Make it similar to the stock layout, but stronger with a larger ring- and-pinion, lower gears, beefier axleshafts, and giant constant velocity joints. We went to Dynatrac, purveyor of fine solid axles such as the ProRock series 44, 60, and 80, and discussed our plan. We decided on a high-pinion ProRock 60 front centersection. We then took this nodular iron centersection back to Randy Ellis Design and began fitting it into the stock front housing location. What is neat about IFS is that the front axle can be built very close to the engine, since all the front suspension movement is outside the framerails at the A-arms, resulting in great ground clearance under the differential. Ellis made spacers to move the engine up half an inch in order to get the larger differential and axleshafts in the exact same position as the original units. This resulted in slightly over 1⁄4 inch of space between the engine and front differential at the tightest point. The ProRock 60 housing from Dynatrac is designed for maximum ground clearance when used as a solid axle; however, we wanted extreme clearance along the top of the casting to clear the engine oil pan. This was achieved by taking an old housing and chopping away at it until it fit nicely beside the engine. Dynatrac took this mockup and machined a new axlehousing to match the chiseled one to fit in the F-150. To duplicate our chiseled front Pro Rock, Dynatrac digitally scanned the piece, transferred that data into a giant mill, and whittled away material from a new centersection. Because the front differential will still be offset to the driver side, a long tube is pressed into the passenger side of the casting. Just like a normal axle, our IFS housing is pressed together in a massive press at Dynatrac’s facility. The inner axleshafts will be retained in the housing with a pressed-on bearing and retainer plate similar to a rear semifloating axle. The tubes are plug welded for retention. We will eventually return to Dynatrac for a fresh set of Dana/Spicer gears and ARB Air Lockers, but first we need to build brackets to mount the housing so we returned to Randy Ellis Design.
We mentioned the EPAS in a previous issue and commented on how we were not confident it could survive 40-inch tires, since Ford doesn’t even use it on its own Raptor off-road trucks. This is our solution: a massive 3-foot-long double-ended hydraulic steering ram from The Off Road Connection. The EcoBoost engine has no provisions for a power steering pump, but through the assistance of PSC Motorsports we sourced a small power steering pump, a reservoir, a cooler, and a steering valve to control the giant ORC ram. Ellis then engineered a mount and idler to run the pump off the secondary air conditioning serpentine belt. Ellis also devised a mount for the orbital valve, tying it into the stock steering column. The hydraulic power steering system will be filled with hot fluid under very high pressure; it is always safest if you run this type of system to mount all the hoses, pumps, and valve outside of the passenger compartment where a leak or puncture is less likely to spray occupants with hot steering fluid. The ram will mount to the crossmember just in front of the front axlehousing. This space, along with all the clearances around the axlehousing, engine, and power steering, is quickly getting tight. But again, these parts should not move much, if at all, so tolerances can be close. The axlehousing itself is mounted off of three points: a mount on the driver-side bearing retainer plate, a properly welded point near the pinion, and a point along the passenger-side tube. All mounts are securely gusseted and tie into factory frame mounts. The next step in the front suspension is building the front A-arms and steering knuckles. These components are all built from the boxed chromoly plate we sourced through Competitive Metals. Various material thicknesses with an elaborate inner structure will result in bash-proof components. The knuckles are also built from chromoly with a bell from Spidertrax. This bell is used in many of Spidertrax’s axles utilizing a heavy-duty unit bearing, but we opted for a Dodge Free-Spin unit bearing replacement kit with a rebuildable spindle and hub system from Dynatrac. This allows us to run a set of Warn hubs and offers a very short mounting surface in order to keep the truck from growing excessively wide. The inner constant-velocity joint is a huge series 30 CV available through RCV Performance. These are capable of nearly 30 degrees of angle, have a diameter of approximately 6 inches, and use massive intermediate shafts almost 13⁄4 inches in diameter at the splines. Often used in high-horsepower desert race buggies, they should be plenty strong for our trail machine. There is much more to come on the specifics of this custom front suspension, not to mention all the other exciting upgrades going into this truck, but we’re out of space for this month. Check out <a href="http://4wheeloffroad.com" xmlns="http://www.w3.org/1999/xhtml">4wheeloffroad.com</a> and our Facebook page (<a href="http://www.facebook.com/4wheeloffroad" xmlns="http://www.w3.org/1999/xhtml">www.facebook.com/4wheeloffroad</a>) for sneak peeks from both the buildup and the Ultimate Adventure trip.
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