If you're considering doing a solid axle swap on your truck there are a few things you need to know. This modification is not for the faint of heart. If you decide to do it yourself, you will be grinding and welding and cursing well into the night if you're not careful.
There are a number of off-roading websites with huge knowledge bases that are extraordinarily helpful when it comes to the specifics of your truck. These forums and guides are a great resource, as someone has undoubtedly made the mistakes for you already, and will be able to steer you clear of them. Before you get started though, you need to decide if a solid axle swap is really what you want to do.
The most important question you need to ask yourself is "Where do I drive my truck?"
This seems like a dumb question, but doing a solid axle swap will dramatically affect your ride quality, ride height, and overall handling.
Let's try to think in pictures. A solid axle runs straight from one wheel to the other, encased in a hardened steel tube, and attached to your truck by two leaf springs, the steering linkage and the driveshaft.
Stock axles have a variety of steering stabilizers and sway bars, but if you are doing a swap you will generally not have these in the first place, and you wouldn't want them, since they limit your articulation.
Which leads us to the first problem with a solid axle swap. You are losing all the equipment that makes your front end ride smoothly at high speeds! And, smoothness equals safety when you are doing eighty miles per hour.
A solid axle has more articulation, which is better, right?
Sure, but on flat ground your body moves instead of your axle, something I don't want happening while I try to hug a corner or downshift into a turn. Increased articulation is the same as increased body roll in this case.
If you're truck spends most of its time on the road, the highway, taking you to work and school, an independent front suspension is far more manageable to drive and can still be upgraded for some hairy off-roading.
Now that sounds like a horrible idea! Who would do that to their nice smooth truck?
Let's think in pictures again, an independent front suspension has no super strong steel casing, and is not straight from wheel to wheel. This is where CV joints come in. Similar in principle to the joints you find in your driveshaft where it bends, they allow your wheels to move up and down independently, while still delivering power. This gives you a softer, more stable ride; if one wheel hits a pothole, the other has no idea what happened.
With a solid axle, the whole assembly angles down and then back up, forcing both your leaf springs to flex and transfer most of that energy straight to the seat of your pants. Coil-over shocks or torsion bars, (depending on your truck) are much better at absorbing that energy than leaf springs, this is why race cars don't have solid front axles.
But, a truck isn't a race car, and a CV joint sure isn't a hardened steel casing. CV joints are the most common breakage point for independent front suspension in my experience. And, there are few things more annoying than replacing part of your front axle on the trail, you have to take your whole locking hub and wheel off!
Where solid axles shine is in really rough terrain, deep ruts, and rock crawling where extreme articulation is required. A quick Google search will show you how ridiculously far some axles can travel; over twice as far as an expensive long travel kit for independent front axles. No CV joints to break, no control arms to twist, no ball joints to lubricate, the list goes on.
Solid axles also have the benefit of being easy to lift. You want it higher? Slap some different leaf springs on there and you can get as much as twelve inches of lift, maybe more. Not enough ground clearance? Solid axles are strong enough to turn tires as large as you can fit, lifting your differential way off the ground to clear those big rocks and logs.
Whether or not you want to do a solid axle swap is a tough decision for many, but it really comes down to what you want out of your truck. A trip to the Rubicon with independent front suspension is probably a bad idea; a solid front axle will net massive gains in height, flex, and durability. Flying down the highway and maneuvering through corners is far more manageable with independent front axles, but a deep rut or bad entry angle can spell disaster for your truck's tender bits.
The best advice I can give you is to seek out those online resources specific to your truck! My 1987 4Runner handles trails far beyond what I expected out of an independent front suspension. But, I always keep spare CV joints and a full set of tools, and they get plenty of use out on the trail. In contrast, my trail partners all have solid axles and if they pull their tools out, it's only because they still have stock support hardware like U-Bolts and brake lines.
I am reluctant to bash independent front suspension for four wheeling. Most truck companies have switched entirely over to this suspension setup for their personal vehicles, and they have done an amazing job improving its durability and effectiveness. Modern trucks are incredibly strong and the situations where you need that solid axle are generally tougher than most people will want to tackle. Before you take on this project, I highly recommend that you attempt the trails you would like to drive. With the appropriate modifications you can handle much more than you think.
A set of two inch ball joint spacers and new shocks will give you the clearance you need for thirty three inch tires. If you want to preserve your CV joints, there are aftermarket kits that allow you to drop your differential and sway bar. This lowers the angle on your CV joints, reducing stress when under power and ensuring that you keep your tools in your toolbox, where we all like them to stay. Do your research and keep in mind what you want your truck to do!
Tailor your truck to your needs, and you will rarely be disappointed. Doing a solid axle swap on your daily driver will net you little more than a tall hood and a sore bottom.