Hubs ExplainedDate: 2002, May 11
Author: Tad Grosvenor
Description of Hubs and what your Isuzu has
First of all, all Isuzu SUVs are primarily rear wheel drive, with a selectable on-off front axle. TOD is the only exception to that, but I'll get to that later. Now, when you are driving in rear wheel drive, the front wheels are just rolling. No engine power is being delivered to them. This helps with efficiency (gas mileage) and power (acceleration) not to mention reducing wear on the tires.
The first kind of hub that Isuzu used was an automatic locking hub. This meant that the front axle shafts, differential and front driveshaft were not turning during normal street driving. The truck was 2wd most of the time. To engage 4wd, stop the vehicle and shift into 4wd. This engages 4wd in the transfer case. Now the front driveshaft turns when the rear one does. This means that the front axle shafts and differential are also now turning. When an automatic hub recieves power from the axle that is is connected to, it engages. This is why the truck needs to be stopped when 4wd is engaged; when you start moving from a stop the hubs engage. Doing this at a slow speed ensures that they don't get a huge force from the drive axles, slamming them into engagement. Once the hubs are engaged the power that is sent to the front axle is now being transmitted to the wheels. 4wd is working.
To disengage 4wd, stop the vehicle, shift out of 4wd and then back up about 4'. This causes the front wheels to be pulled backwards away from the direction that the hubs were "pushing" them (for lack of a better term). This is where the hubs unlock. Then you can continue forward without the front axle causing un-necessary drag.
The big drawback to automatic hubs is that they have to un-lock and then re-lock when changing directions. So lets say that you are driving forward, in 4wd. The vehicle then gets stuck in some deep snow. You shift into reverse to back out. As soon as you start pressing on the gas to move backwards, the front axle shafts turn in reverse. This first unlocks and then relocks the hubs. In a properly cleaned and lubed hub, this only takes about 1/3 to 1/2 of a revolution of the wheel. When things get dirty or the hub gets stuck (most often due to dirt) this distance can be longer. It is also possible for the auto hub to not re-lock at all. Again, proper maintenance can prevent hub problems, but it is something else to pay attention to.
This unlocking mechanism is where the problems with automatic hubs start. Most people will never have a problem with automatic hubs. If they do, the most common problem is a clicking or "grinding" from one or both front wheels. This is caused by the hubs only partially engaging or disengaging. This can usually be fixed by "repacking" the front hubs. This is done by taking them apart, cleaning them and regreasing.
The other REALLY BAD clicking is caused by something else altogether: the axle shaft slipping inside of the hub. The axle shaft is splined, and the inside of the hub is also splined and fortunately for us those splines match. The axle shaft is held into the hub by a c-clip. This clip snaps into a groove in the end of the axle shaft, after the shaft has been slid through the workings of the hub. When the c-clip breaks or comes off, the axle shaft can then partially slid back out of the hub. When this happens there is only 1/3 to 1/2 of the splines making contact. When you apply power to the axle shaft, and there is this less contact area, the axle can actually slip inside of the hub, grinding the splines off of the axle shaft. This is the "BAD" poping that can be heard when someone is off-roading with a broken c-clip. This isn't often heard on the road because even in low traction on-road situations there isn't an extreme amount of pressure on the front axle. Off-road things are different and often the truck is being moved by the front axle. POP POP POP.
Once this has occured, there is some damage to the truck. The splines on the axle have been at least partially rounded off, and there is also a decent chance that the hub has been damaged as well, either by the bits of axle shaft metal floating around in the grease, by part of a broken c-clip being caught in it, or by having some of the splines ground off of the inside of it by the axle shaft. Some manual hubs can be swapped onto a damaged axle and will still have enough contact area. Factory Aisin are the type that I know of that can be swapped with the autos when this occurs.
Please don't confuse this with the click-click-click of a failing CV joint. That clicking is really only heard when making tight corners. Hubs can make the poping noise when the tires are straight.
Isuzu started using manual hubs in 1988 on the automatic transmision Troopers (with the 2.6l 4cyl engine). Also, 1st gen 4wd Amigos also have come with manual hubs (1989-1994).
The real benefit to manual hubs are their simplicity. They are either unlocked or locked. You as the driver set them. Once a hub is locked, it won't just come unlocked. They are faily simple, and can be taken apart and cleaned in a few minutes.
There are 3 brands of manual hubs that will fit 88-03 Isuzus. They are:
Aisin: These are the factory hubs. They are low profile, VERY strong, and easy to work with. The downside is that new from Isuzu they are extremely expensive. The upside is that buying a used set of Aisins is an option. There isn't anything that can really wear out inside of one of these hubs. Unless they have been allowed to sit and rust into one solid block, odds are that they are fine. Taking them apart and cleaning them was documented by Planetisuzoo member Bruce Anderson at: http://myweb.cableone.net/bcanderson/trooper/manual%20hubs/manual%20hubs.html
Warn: These are popular, however a few Planetisuzoo members have reported problems with them and their stamped steal internals. If you can't find a set of used Aisins, Warns are available new. The downside is that they can't be swapped onto some Isuzus that came with SOTF. The axle shaft on SOTF Isuzus isn't long enough, and the c-clip groove doesn't exist in the shaft. Be sure to buy from some place that will let you return them if they don't fit. Also, but the Warn premium hubs. The internals are more metal than plastic in those.
Superwinch: Again, these are available new. Some have complained of too much axle slop, but you should be able to shim that slop out. They use small allen-head cap screws to hold the cap on, and some people have stripped those out when they tried to remove the cap. You will also have to find 2 26mm c-clips (external) to hold these onto the shafts.
Hub flanges are what you will find on all SOTF (Shift on the fly) and TOD (Torque on Demand) Isuzu trucks. They function exactly like a manual hub, except that you can't unlock them. They can be swapped for manual hubs, you will just have to remember to lock the hubs before you try to turn on TOD or shift into 4wd. They look like a 3.5" round plate with 6 allen-head bolts holding them onto the center of the front hubs. If you are removing these and installing manual hubs, you can re-use the snap rings if you wish.