To Float, Or Not To Float? | Full-Floater and Semi-Floater Rear AxlesPosted in How To on November 1, 2012
What’s the difference between a full-floater rear axle, and a semi-floater? More importantly, do you need a full-floater?
We’re only talking about rear axles here. Front axle systems, whether solid axles, Ford Twin Traction Beam, or A-arm IFS, are all full-floaters by definition. If this seems confusing, the next few paragraphs should shed some light on what makes a full-floater a full-floater.
In short, a full-floating rear axle mounts the wheels to wheel hubs, whereas a semi-floater mounts the wheels to the axleshafts. With a full-floater, the hubs bear the vehicle weight, not the axleshafts. In contrast, a semi-floater places the vehicle weight on the axleshafts.
Inside a full-floater, the axleshaft has only one job: to turn the combined hub and wheel. Inside a semi-floater, the axleshaft has two jobs: support the vehicle weight as well as turn the wheel. Break a full-floating axleshaft, and the vehicle will still roll and support its own weight. Break a semi-floating shaft and you might lose a wheel and find yourself dead in the water.
Full-floaters are stronger, but they’re also slightly heavier (old-school OEM full-floaters are much, much heavier) and noticeably more expensive than their semi-floating counterparts. The flip side of the coin says that semi-floaters aren’t as strong, but they’re lighter weight and less expensive than full-floaters.
Do you need a full-floater? Full-floaters are perfect for heavier vehicles and/or abusive applications. Lighter vehicles and mellower applications work well with semi-floaters. There are also vehicles whose ABS, speed sensors, and traction control systems aren’t compatible with the full-floaters currently on the market.
So, do you need a full-floater? If your vehicle and your pocketbook are compatible with a full-floater, we’d say “yes” every time. The reliability and peace of mind are worth the price of admission. If a full-floater isn’t for you, you should know that semi-floaters are successfully used in fullsize trucks as well as abusive applications. It’s just that semi-floaters don’t have the same “safety net” that full-floaters provide.
To illustrate the differences between the axle types, we visited the new Currie Enterprises shop in Corona, California. Currie offers both full- and semi-floating axles to fit a wide variety of stock and custom applications. We also dropped by Total Chaos Fabrication to see a Currie full-floater under their “Lil’ T” Tacoma race truck, and finished off the day by checking out an old-school OEM-style floater that’s common to one-ton full-size trucks.
To float, or not to float? This info should answer the age-old axle question.
01. A semi-floating rear axle assembly features a wheel-mounting flange on the outer edge. Via this flange, the wheel mounts directly to the axle shaft. The wheel bearing is pressed onto the axle shaft, and the axle-and-bearing assembly bolts into the housing end. Housing ends are available in different styles, but they share a common fate: they’re welded onto the ends of the axle housing tubes. A second semi-floater style is not shown. It’s a C-clip style, and uses C-clips inside the differential to retain the axle shafts. With a C-clip assembly, wheel bearings are pressed into the axle housing ends, and the axle shafts slide into place inside the bearings. With a C-clip semi-floater, the wheel and axle can (and do) fall off the vehicle if the C-clip or axleshaft breaks. For this reason, a pressed-bearing semi-floater is more desirable than a C-clip semi-floater.
02. The difference between a semi-floater and a full-floater is hopefully clear by now. Here’s a full-floater hub with its matching spindle. Just like the semi-floating housing end seen previously, the full-floater spindle is welded to the end of the axle housing tube. Be aware that the term “snout” is also used to describe the spindle.
03. The semi-floater axleshaft, with its wheel-mounting flange and pressed bearing, is on top. A full-floater axleshaft, with splines on both ends, is seen below. Either style can be made in custom lengths to match custom-width axle assemblies.
04. Currie Enterprises offers full-floating axle assemblies (also called “rearends”) in three varieties. On top, there’s the “JK Floater” which is compatible with the Jeep JK Wrangler’s rear disc brakes, parking brakes, and electronic systems. The JK Floater is also well-suited for non-JK applications. The “Unit-Bearing Floater” sits in the middle, so-named because it uses the unit bearings from a Ford F-450 Super Duty front axle. Beneath the JK Floater and the Unit-Bearing Floater is a new style from Currie, which we’ll call the “Prerunner Floater” for lack of an official term. The Prerunner Floater uses a 2.5-inch spindle and a matching custom aluminum Currie hub. This style is common on many prerunners we’ve seen and can be adapted to several popular performance braking systems.