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Thursday, Sep 2, 2010
| Off-Road.Com Tech Sectoion Question and Answer'sQ: How do I learn to drive offroad?Q: How do I find other people or a 4x4 club to go 4 wheeling? Q: What are hubs and why are they locked and unlocked? Q: How do you interpret metric tire sizes? Q: What is the difference between semi- and full-floating axles? Q: How do I learn to drive offroad? ( by Stefan Roth Q: How do I find other people or a 4x4 club to go 4 wheeling? ( by Stefan Roth Call UFWDA at 1-800-44-UFWDA(83932) during the day or early evening. They can give you the phone number of your state or regional association, which can then tell you about clubs in your area. You could also just join an association, but clubs have more meetings and trail rides. Even if a club is 50 or 100 miles from you, you can attend their weekend trail rides without too much trouble. It's also a good idea to join UFWDA as an individual. Their cheapest membership is $15 and you get a really good newspaper from them that tells you about 4WD activites and ideas from clubs across the country. Q: What are hubs and why are they locked and unlocked? ( by Stefan Roth and others ) Locking hubs are the devices in the center of your front wheels. Hubs are a locking mechanism that connect or disconnect your front axle from the wheels. In the rear, your axles are always connected to the wheels so you do not have hubs. There are three major categories of hubs: permanently locked, automatic, and manual. There are also variations, but there are too many to cover in this FAQ. The Jeep Grand Cherokee, for example, has permanently locked front hubs. It means that the wheels are always connected to the axles. So when you are in 2WD mode (the transfer case has been disconnected from the front driveshaft), the front wheels spin the front axles, which spin the differential, which spins the front driveshaft. You get more component wear on the entire front drive mechanism and lower gas milage, but this effect is very minimal. Remember, the rear drive mechanism is also used for the entire life of the vehicle. In my opinion, this configuration is better than most automatic hubs. Automatic hubs come in many different configurations, depending on manufacturer. Generally, only one side unlocks, so the other side's axle always spins. I consider this to be the least desireable of the available choices, though there is nothing wrong with them. For some people, this may be the best choice. You do not have to operate the hubs, they lock and unlock automatically when you switch the transfer case between 2WD and 4WD. Some people complain about this system because the driver does not necessarily get any positive feedback if the locking/unlocking was successful. When manual hubs are unlocked, the wheels are disconnected from the front axles. Thus the front drive mechanism does not move when in 2WD. The driver must get out of the vehicle and twist the dial on each of the hubs to lock or unlock it. You can leave the hubs locked even when in 2WD and the effect will be similar to the permanently locked hubs. Many people do this during the winter or when offroad all day. There are also the lock-o-matic hubs (mine are from Warn). They have been around for many years now. Some people called them ahead of their time (translations: never caught on). They are like manual hubs, except in "free" mode, they engage if you put the transfer case into 4WD and disengage when in 2WD. In "lock" mode, they stay locked. Like all things, they have their advantages and disadvantages. There are no locking hubs on rear wheels. The rear wheels are directly connected to the axles. Some people modify their vehicles and install manual locking hubs in the rear so they can unlock the rear wheels from the axles; this is very rare and usually done for towing purposes. Q: How do you interpret metric tire sizes? ( by Gregory M Charland Q: What is the difference between semi- and full-floating axles? by Stefan Roth Dan Hepner Eric Thompson Nick Leiterman June 1993 All of the below assumes you have live axles, not IFS. Basically, on 4WD vehicles, the front axles are full-floating axles, meaning that the wheels are mounted on their own bearings (2 per wheel). If you break the axle shaft, your wheel does not fall off. The reason is that the wheel is not directly attached to the axles. If you FREE the hub, they aren't connected at all. If you LOCK the hub, a splined sleeve just slides in to connect the axle and wheel. In the rear, on most vehicles (especially half ton or less), you have semi-floating axles. Sometimes there is a C-clip at the differential that keeps the load from being put on the axle at the differential. These axles generally do not have any hub whatsoever in the wheel. If the axle is a C-clip axle and the axle breaks, the wheel will fall off. If the axle doesn't have a C-clip (like most axles), the axle is held in place basically by the four bolts on the brake backing plate. This plate holds the bearings and races in place so that if the axle breaks, the wheel will PROBABLY not come out. It is possible that a loose wheel could easily break a flimsy brake backing plate or the bearing/race assembly could become unpressed from the axle shaft itself. In this case - you now have a tricycle. For example, a Scout has DANA 44 axles in the rear (and front) and it is semi-floating (full in front). The Scout DANA 44 has a plate that is bolted to the axle housing flange with 4 bolts. The plate holds the wheel bearing in the housing. The only thing holding the axle in is the press fit of the wheel bearing and collar on the axle shaft. If the shaft breaks, the wheel will not come off, but the loading of the wheel bearing will change. It may or may not be possible to drive the vehicle. A semi-floating with external plates for bearing retainers will lose a wheel if the axle breaks at the bearing (for example if the bearing goes out). On a Chevrolet Astro van's semi-floating axle, the axle shaft is held in by a C-clip in the differential. If the shaft breaks, the wheel will fall off. A Toyota Land Cruiser has the C-clip at the differential. A Ford 9", which is also described as semi-floating, has no C-clip but instead has a flange at the axle end that bolts to the housing and ATTEMPTS to hold the wheel on should the shaft break. However, early model Broncos have been seen on the side of the road in 3 wheel mode. Most 3/4 tons since about 10 years ago have come with semi-floating axles standard, and full-floating as an option. Before that, 3/4 ton and above trucks and vans generally have floating axles in the rear. You can tell by looking at the hub. If there is a hub (without a dial), then it's generally a full-floating axle. The exception is if someone just has a large decorative cap in the middle of the wheel. The hub has to be a hefty looking cast steel cylinder, just like on the front of 4WD vehicles. Full-floating axles are generally constructed stronger because they are meant for heavier duty applications. The floating axle design by itself is less prone to axle breakage because all the weight rests on the wheel bearings and not on the axle. There's also a different (stronger) style of bearing, a set of two tapered roller bearings. The disadvantage is that it weighs more so you have more unsprung weight. To carry the description a little further, just look at a full-floater as another front axle without steering knuckles. The full-floater has a spindle that bolts to the axle housing; the hub mounts to the spindle just like a front hub, with its own bearings. All weight is supported by the housing, not the shaft. The shaft is inserted through the housing into the differential side gear on one side and a cap on the wheel end supports the other end of the shaft and transfers power to the wheel (like a lockout that doesn't disengage). Since the shaft doesn't ride on a bearing but is suspended between the diff gear and the hub, they call it full-floating. Everyone considers full-floating axles to be superior. There's no doubt they're stronger due to the superior wheel bearing setup. This is of most significance while carrying heavy weight, but can't hurt in other situations either. Also, they're easier to work on, as the entire mechanism comes apart turning nuts and bolts, with no pressed bearings. DANA 60 axles, the next size up from DANA 44, are considered 3/4 ton axles. Dana 60s have been made both full and semi-floating, and it may well be that there have been more made semi-floating than full floating. '60s Chrysler product cars with the 426 hemi ran semi-floating 60s, and the standard 3/4 ton Dodge rear-end today is a semi-floating 60. A DANA 70 axle is full-floating and generally used for 1 ton applications. Ford, Chevy, and Dodge use DANA axles for their various pickup trucks, though they may have custom versions of them. Ford also makes their own axles (8.8", 9", 10.25" ring gear, etc). The basic definition of the different types of floating axles are: o Full-floater "floats" both ends. o Semi-floater "floats" the differential end and uses a pressed bearing at the wheel end. o Non-floating would have pressed bearings at both ends (though such a configuration may not exist). As a little side note, there was an article in Four Wheeler where they replaced the rear wheel hub with Warn lockouts, making the vehicle tow easier. The vehicle they did this to used the same spindles front and rear, they bolted a spindle and hub to the tire rack, mounted the tire to the assembly and ended up with spare parts (spindle, hub, bearings, lockout, etc) to repair whatever broke on any one corner of the rig. |
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