|Authoring and Photography By: Chris Perosi
First Published: February 2000
Installing Manual Hubs on a 1996+ Isuzu
|Manual hubs installed on a 1998 Amigo, in place of the original drive-flange.
In 1996, Isuzu Motors, Inc., made the decision to equip their 4x4 vehicles with a Shift-on-the-fly (SOTF) 4-wheel drive system. In order to accomplish this, the mechanical hubs (manual or automatic) were removed from the front wheels and replaced with a hub drive-flange, which is bolted to the end of the axle. This turns the axle continuously, regardless of whether the vehicle is in 2WD or 4WD. Instead of disconnecting the front axle at the hubs, as was previously done, a disconnect was placed in the driver’s side front axle half-shaft. This disconnect is vacuum-actuated by pressing the "4WD" button on the dashboard, or by using a shift lever, in some of the older trucks, which slides the splines inside one another to engage the axle. The result is that 4WD can be engaged by pressing a button on the dash, while traveling forward at up to 60 MPH. Switching back to 2WD is just as easy. Just press the button and you’re back to 2WD, without backing up to remove drivetrain-bind, as is commonly associated with manual or auto-locking hubs.
This system works very well in day-to-day, on-road use, however, it is not without its drawbacks. The largest drawback is that the CV-joints that drive the front wheels are always spinning, regardless whether the vehicle is in 2WD or 4WD. This creates added wear-and-tear on the joints themselves and the boots covering them, a problem that is simply compounded by the steeper angles created by a suspension lift. In addition to the wear-and-tear, the engine is forced to push these CV-joints (and the axle halfshafts attached to them) all the time, taking its toll on the truck's use of available horsepower. Gas mileage suffers as a result.
While most SUV drivers probably wouldn't care much about all of this, even a casual off-roader should be concerned with it. The CV-joints are one of the most common problem areas on IFS trucks, especially lifted IFS trucks, and they should be treated with great care. This simple and inexpensive modification is something just about anyone can do to exponentially increase the service life of the CV-joints, as well as to recapture some lost power and gas mileage.
|Jack the vehicle up and support it using jackstands, then remove the tire.
Part 1: Preparation
Obviously the first step in an undertaking such as this is getting the parts ready. To complete this mod, you’ll need a set of manually-locking hubs. You can either get a set of new Superwinch hubs or you can get a used set of AISIN hubs from a salvage yard. The AISIN hubs were original equipment on any Isuzu from 1988-forward that was equipped with manually-locking hubs. Both brands are good units – Superwinch is a well-known and trusted brand, and the AISIN hubs are generally thought to be bullet-proof in the off-road community. Many feel that the AISIN hubs are slightly more watertight and made with better-quality materials, however, those same people are quick to note that the Superwinch hubs are a good choice as well.
If you decide on the Superwinch hubs, the best bet is to buy them new. You can probably find a set of used hubs somewhere, but you won't likely save much money, and they'll probably require a rebuild. As of January 2000, the Superwinch part number needed is 400533.
|AISIN manual hubs and the factory drive flange compared side by side.
If you choose to get the AISIN hubs, obtaining them new is a very expensive proposition, so you're much better off getting a set at your local salvage yard, or from H&I Salvage (an Isuzu salvage specialist) in California. Price will vary, and could be more or less expensive than a set of new Superwinch hubs. The downside is, they may require a rebuild before they are in useable condition. Rebuilding them is not that difficult -- detailed instructions on rebuilding these hubs will be added here soon.
Once you have the hubs, the only other thing you'll need are the tools to accomplish this task:
Once you've gathered all these parts, set aside about an hour of time, and go to it.
Part 2: Removal of Stock Hubs
|Remove the six allen-head bolts holding the drive-flange on the wheel hub.
The hub drive-flanges on the SOTF trucks are easily removable. Simply jack one of the front tires up, and remove the wheel. Once the wheel is off, you'll see six allen-head bolts holding the hub drive-flange on the end of the axle. You may need to tap the allen wrench with a hammer to get them moving, but they'll come off with some persuasion. Remove all six of them, and set aside the flange cover. At this point, the only thing holding on the hub flange is the snap ring. Remove the snap ring, watching carefully so that it does not come off unexpectedly and roll away into the unknown. The drive-flange should slide off the end of the axle easily.
|Apply a bead of RTV sealant around the entire mounting surface, being careful to keep a continuous line. Be sure to stay to the inside of the bolt holes.
After removing the drive-flange, it's a simple task to put the new hubs on as well. Separate the cover plate from the hub body, and apply the liquid gasket-maker to the wheel flange and to the backside of the hub body. Let it gum up a minute or two, then press the two together and install the six bolts. Carefully wipe off any excess gasket-maker from the seams, and torque the bolts down. Now, reinstall the snap ring on the outside of the manual hubs.
Once the hub bodies are on, all that's left is installing the cover plates. This could be a little tricky if you're using the AISIN hubs, because you'll have no instructions to go by, and the covers can only be installed in one direction; however, they'll slide on in two or more directions. Because of this, it's a good idea to place the cover over the hub body with a couple of loose bolts in order to test it. Turn it from free to lock and back a few times to verify the positioning. Once you're certain of the correct placement, mark it, then remove the cover plate and apply more gasket-maker to both surfaces. Again, let it coagulate a little, then install the cover and the six cover bolts using a 10mm socket. Gingerly tighten the bolts using a torque wrench, as they have a torque specification of only 12 lb-ft.
Once the installation is complete, replace the tire and wheel assembly. If you have center caps on your wheels, you'll need to remove them so that you'll have access to the locking mechanism. Once the wheel and tire are back on the vehicle, you'll be able to easily see if you've done everything right. Just give the tire a spin. With the hubs locked, you'll clearly see the CV-joints inside spinning around with the tire, and you'll note that the tire loses momentum very quickly. In the "free" position, on the other hand, the tire will spin freely, independent of the CV-joints.
Repeat the process on the other side, then go out and find a trail where you can test them! Just be careful of submerging the new hubs for the first 24-48 hours. The gasket maker needs time to setup, so the hubs won't be completely watertight for a day or two.
Part 3: Results
As a result of installing the manual hubs, you'll notice some interesting results right away. First and foremost, you'll notice that you have to get out of the truck to lock the hubs when you hit the trailhead. Not exactly a benefit, but not a big deal, really, when you consider that you have to air down and maybe disconnect the swaybars when you get there as well. More importantly, though, you should notice a slightly better "seat-of-the-pants" feel when you step on the gas pedal. The engine is using its horsepower more efficiently, so you'll feel like it's making more power. Don't expect miracles here, but if you're in tune with the truck's power, you will notice the difference.
In my personal experience, I've also noted a 1 - 3 MPG increase in my gas mileage. Since gas mileage varies greatly based on driving style and habits, as well as individual conditions, you may or may not notice as much of a change. In theory, at least, you should get better mileage out of it, since the engine no longer has to push through the CV-joints to turn the front wheels. In the very least, it certainly won't have a negative effect on gas mileage.
In the long-term, the CV-joints and boots should enjoy a much longer, happier life, especially on a lifted truck. Since they're no longer spinning constantly, they will not be experiencing any wear-and-tear for the large percentage of the time that the vehicle is in 2WD on the road. The only time they'll be in use is when the vehicle is in 4WD.
The installation of manual hubs opens up a unique opportunity on these particular vehicles: a front locker. Some vehicles cannot run a front-end locker without extensive modifications due to their front differential or hub design. However, on this vehicle, none of that stands in the way. The only real problem created by a front locker on this vehicle would be turning radius problems in 4WD. With the manual hubs, however, one of the hubs could be unlocked in tight turning situations, leaving the vehicle to differentiate through the turn as needed.
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