Posted by MikeC on Thursday, July 18, 2002 at 1:16PM :
In Reply to: Full floater rear end vs semi floater rear end posted by Tug Boat Lonnie on Thursday, July 18, 2002 at 12:59PM :
Any drive axle no matter what kind, has to perform two functions. The first is to support the weight of the vehicle safely, and second to turn the wheels and propel the vehicle forward.
Most half-ton and lighter vehicles are typically equipped with a semifloating rear end. In a semifloater the wheel bolts directly to a flange formed at the end of the axle shaft. A single bearing supports the outer end of the shaft and is located just inside the housing ends. Therefore, the axle shaft itself has 2 forces acting on it at all times. It has the weight of the vehicle with payload pushing down on it , and the force of the engine twisting on it.
In heavier applications like 3/4-ton and heavier trucks, semifloaters are much less desirable because the heavier weight of the vehicle combined with the twisting forces can cause a semifloating shaft to bend or break off. Obviously having your rear wheel pass you on the road can be somewhat unsettling. To prevent this from happening fullfloaters use an axle housing with a spindle formed at the end of the axle tubes. The wheel is bolted to a separate hub which spins on 2 opposed tapered roller bearings. Since the weight of the vehicle is supported by the spindle on the housing and not the axle shaft, the shaft is only subjected to twisting forces from the engine.
Which is better? Fullfloating setups are a must for 3/4-ton and heavier trucks. They may also be a good idea for 1/2 ton trucks that haul a lot of weight or tow heavy trailers. However, except for custom-built axles, virtually all factory full floating rear ends use eight-lug wheels. So if you've fallen in love with a five- or six-lug wheel, you may be better off with a stronger semifloater to upgrade your truck. As far as front drive axles are concerned, don't worry, all front drive axles are usually fullfloating. Dynatrac specializes in custom built Dana 60 rear ends in fullfloating and super-duty, semifloating versions to accommodate a broad range of applications from Jeeps to 1-ton trucks.
And before you go thinking that I knew this off the top of my head, I just copied it from the link below.
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