2WD to 4WD Ford Conversionby Richard Rowe
Ford trucks and vans are well known for their versatility, off-road prowess and on-road manners, but one aspect of Ford's do-it-all model line is often overlooked. Ford has always had a very modular approach to model diversification; it's not uncommon for chassis and drivetrain components from different models and vehicle types to cross overs to others in the same range, which is what makes the prospect of a 4WD conversion for 2WD chassis such a tempting proposition.
Whether you're taking the "buy it as a kit" or "junkyard crawl" approach, you're going to need the same basic parts. In general, you'll want to stick with trucks or vans in the same model range as your own; F350 truck parts fro E350 vans, F250 parts for E250 vans, etc. In no particular order, you'll need: Complete front axle assembly with gears to match you existing rear axle, locking hubs, 4x4 brake rotors/steering linkages.springs/radius arms, transmission hump plate, front and rear drive shafts, transfer case skid plates, 4x4 speedometer cable/transmission tailshaft/output shaft and transfer case. The conversion should run you between $2,000 and $4,000, depending on your chassis and parts choice.
Transmission and Transfer Case
There are two routes to go for when choosing a transmission and transfer case. You could use adapt your stock gearbox for use with a 4x4 transfer case, but purchasing and installing a factory built 4x4 powertrain is usually simpler, cheaper and creates less opportunity for mistakes to occur. In the time it would take time you to remove the output shaft assembly from a donor tranny and installing it in your current one, you could already have had a new tranny installed and running.
Order of Construction
The entire modification centers around your new transfer case, so that should be the first thing installed. Move from there to the rear suspension, then the front suspension. The front suspension is where most of your fabrication work is going to take place; F350 and 250 models will require complete removal of everything that moves, so be prepared for some torch time. Most F350 owners find it easier to replace the entire front clip, but that's up the the individual.
The four-wheel drive system is going to add some weight; about 350 pounds, in fact. Add to that increased weight the rotational drag and inertia of a 4WD axle and transfer case, and you're looking at a serious drop in performance without further modification. Consider a little engine work. Aftermarket exhaust and intake systems are a given, but you might want to think about going a little further with higher compression pistons and a set of headers. Consider these modifications mandatory if you're running a lower-powered 302 (5.0L) engine. As far as the drive-train goes, a higher stall torque converter would be a good idea, and numerically higher gear ratios will go a long way toward restoring stock acceleration if you're using larger diameter tires.
Richard Rowe has been writing professionally since 2007, specializing in automotive topics. He has worked as a tractor-trailer driver and mechanic, a rigger at a fire engine factory and as a race-car driver and builder. Rowe studied engineering, philosophy and American literature at Central Florida Community College.