Every car has to figure out a way to send all of that torque to at least one wheel. This happens quite differently on an old Civic hatchback compared to an FR-S, like our Ratchet Bunny. But the axles themselves—and how they break—don't change a whole lot.
SAME AXLES, DIFFERENT DRIVETRAINS
- FWD: That old Civic hatchback of yours sends its measly 100 lb-ft or so of torque through its transaxle and to one of its front wheels by way of a couple of axleshafts that span from that transaxle's differential to its wheel hubs.
- RWD: If you've got something with an independent rear suspension like the FR-S, that whole arrangement of axles will look awfully familiar. Like the Civic and its transaxle, here, a pair of axles connects the rear differential to both rear hubs.
- AWD: Everything gets murky here depending on whether you're driving something like an R35 GT-R or an old DSM. With either, you'll find a combination of two axles at each end along with a series of differentials, all of which link up to those hubs pretty much like those FWD and RWD layouts we just told you about.
CV JOINTS AND WHY THEY STINK
Those axles link up to your rear differential or transaxle—which never move—and your wheel hubs—which travel up and down as much as your suspension tells them to. Which means those axles have to be able to expand and collapse every time you do important things like turn or mob over a speed bump. A CV (constant velocity) joint at each end of those shafts is what lets all of this happen and is typically the first thing to fail. The FR-S' specialized joints are made up of a gear-like hunk of metal that pivots inside of a steel race by way of a series of hardened metal balls. All of this is carefully stuffed inside a grease-packed and sealed rubber boot that's got enough flexibility to move when you need it to.
BREAKING AXLES THE EASY WAY
Unless you've got some 8-second drag car with knee-high racing slicks, that axle failure won't look all that impressive. Most of the time the damage is contained to that CV joint's rubber boot that just split and lets you know it has by way of a whole lot of clicking sounds that escalate when turning and not some monumental-sounding snap. Send enough torque to those wheels or generate enough grip at the tires, though, and you just may bust up that CV joint's insides altogether, twist that axle, or—worse yet—snap it in two.
THE WARNING SIGNS
- Clicking sounds that escalate when turning.
- Excess grease on inner wheel, fenderwell, or tire.
- Vibrations that get stronger the faster you go.
- Transmission is in gear but you're going nowhere.
First, be sure the problem's more than just a loose axle nut. You can replace and repack those CV joints for the price of lunch, pop in a set of rebuilt axles for a few more dollars, or just call the people at Driveshaft Shop for something that'll never come apart. As far as our FR-S goes, Driveshaft Shop offers two configurations: its direct-replacement shafts that'll handle as much as 600 hp, and its Pro-Level kit that's good for nearly twice that much. Its 600hp axles are all you'll ever really need, though. The outer joints are made of billet chrome-moly, the shafts themselves are made of 300M—a material so strong you've never even heard of it—and the inner joints are designed from a Porsche to handle the extra punishment.
1. Let the brakes cool, pull the wheels off, and get the car up in the air (duh!). Then you're going to pry up the lock where the axle nut is so you don't mess up the threads.
2. Remove axle nut.
3. Remove the three bolts holding the suspension arm in place (17 mm, 19 mm). Might need some muscle to get 'em loose.
4. While not necessary, AutoTuned recommends undoing trailing arm bolts for easier install. This allows you to move the brake assembly out of the way.
5. The stock axle comes out with some prying and pushing. Once you get a good grip, you can pop it right off.
6. Time to install the beefier Driveshaft Shop axles in reverse order. You're provided a new axle nut, and don't forget to torque it to 160 lb-ft when done. Also, an alignment will be needed afterward since you moved the position of the suspension.