Because of the often-times tremendous difference in prices between 2 and 4-wheel drive trucks some people purchase the 2WD out of necessity, only later to find that they wish they had been able to buy the 4WD. Or, some might even purchase the 2WD on purpose in order to save money up front and then take on the task of conversion to 4WD at a later time.
On the whole, the vehicles covered by this guide make EXCELLENT candidates for this. One of the reasons this is true would be because of Suzuki (and Geo's) approach to building vehicles. For such relatively low production numbers (compared to many of the world's vehicle platforms) it does not make economic sense to build too many unique parts for sub-sets of these vehicles (2WD vs. 4WD or even 2-door vs. 4-door in some cases).
The Samurai, for instance, uses a transfer case whether the vehicle was a 2WD or 4WD model from the factory. That meant every vehicle coming off their assembly line got the same 2 driveshafts to transfer power to the rear wheels (and 4WD models got a third in the form of the transfer case-to-front differential shaft). But more importantly, this means that the owner of a 2WD has one of the major headaches of a typical 4WD conversion already solved. One could easily remove the 2WD transfer case and just bolt the 4WD unit in its place.
One of the vehicles that we tore down in research for this guide was put through such a conversion. One of our editors actually had a 2WD Tracker which was in relatively nice shape, but was not worth selling to replace with a 4WD model. He located a 4WD that had some minor body damage and a bad case of neglect, which, because of these 2 reasons, was selling rather inexpensively.
In case you would like to undertake a similar project, here are a few things we learned during this process. The first and most important thing to do is to get your hands on the manufacturer's parts information. In the case of Suzuki and Geo it is normally in the form of microfiche. Studying the fiche for these 2 vehicles told us that the VAST MAJORITY of parts on this vehicle (even down to most of the suspension and drivetrain) were the same from the factory.
One warning here, we also learned that although certain REPLACEMENT parts were the same, that this may not have been the case during assembly. An example is the front hub and bearing assembly, which showed identical part numbers for both the 2WD and 4WD assemblies, meaning that the halfshafts from the 4WD unit should fit right through the 2WD hubs. And, since the 2WD hub even had the bolt holes for the locking hub components, we figured this was an easy installation. BUT THIS WAS NOT THE CASE. The 2WD hubs on our 1992 Tracker had internal bushings with a smaller inner diameter that the 4WD units, meaning different parts had been used at the factory. This didn't stop us, but it did cause us to change strategies.
The second best thing to do if you want to try this is to buy a donor vehicle (a junkyard candidate is fine, if all of the pieces you want are intact). But a runner, that can be fixed up and sold as a 2WD (which in our case covered the FULL cost of the conversion) is a better candidate.
On the Tracker/Sidekick, we found that only 1 part had to be purchased from the manufacturer; the driver's side mounting bracket for the front differential. This inexpensive part needed to be welded in place in order to install the front differential. But that wasn't bad considering that the front differential had 3 mounting points and the other 2 were already on our 2WD truck.
All other parts in the conversion were taken from the donor vehicle, and they included:
A confession on the hub and bearing assemblies. Because hub removal requires the use of a special spindle nut socket (essentially a spanner wrench in socket form) that is capable of 155 ft. lbs. (210 Nm) of torque, we decided to cheat and found any easy answer (no special tools needed). Considering that we already had to swap coil springs, we just took that procedure a little further and finished unbolting the steering knuckles. We swapped the steering knuckles, taking the hub and bearing assemblies with them.
We were also looking into the installation of aftermarket locking differentials, but could not have that information available by press time.