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Ford 8.8-inch Axle Builder’s Guide

Ford 8 8 Inch Rear Axle
Jay Kopycinski | Writer
Posted November 8, 2013
Photographers: Manufacturers

Just Shy Of Nine

The Ford 8.8 rear axle has been a staple of the Ford Motor Company in passenger cars, trucks, and sport utility vehicles for decades. It was first produced in 1983 and has been a common axle used in place of the venerable Ford 9-inch axle assembly. 4WD applications have included the Bronco, Ranger, Explorer, Expedition, and F-150 pickups.

The semi-floating rear axle uses an 8.8-inch size ring gear held to the differential carrier with 10 bolts. Pinion nut size is 1 1/16 inches, and the axleshafts are retained using C-clips within the differential.

Although not serving up the same beef as the respected Ford 9-inch, the slightly smaller 8.8-inch has held its own as a good medium-duty wheeling axle, especially when used on lighter rigs. The axleshafts have been available in 28- and 31-spline counts. The 31 spline is the stouter of the axleshafts with a 1.31-inch diameter versus the 28 spline’s 1.29-inch diameter. It’s possible to reliably run 35-inch tires on these axles if used sanely, not placed in a severe bind, or overstressed with hard locker use.

Upgrades over the Ford 8.8 would typically be a Ford 9-inch, often built with aftermarket upgrade parts, the choice for which is through the roof. Beyond that, the heavier Dana 60 is a likely hardcore upgrade path, but swaps over to an 8-lug wheel pattern on factory axle flanges.

Aftermarket support for the Ford 8.8 axle is substantial, addressing both the car and truck markets. Gear ratios are available up to 5.71:1. A wide variety of limited slip and locker options, axle upgrades, and brake kits make this axle easy to improve.

Step By Step

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  • As with many factory axles, the stock differential carrier in the Ford 8.8 is fairly weak and can distort or crack under moderately hard use with larger tires. Swapping in an aftermarket differential eliminates this one axle weakness.

  • One of the more desirable 8.8-inch versions is the 31-spline Explorer axle. This is a common swap axle and ends up under a variety of rigs—Ford or otherwise. 1994 and older versions came with drum brakes, while the 1995 and newer axles were equipped with disc brakes. Some 2010 and 2011 model Ranger axles (pictured) were also factory-equipped with rear disc brakes.

  • Aftermarket traction-aiding devices include the Yukon Dura Grip (pictured), Yukon Grizzly, Yukon Trac Loc, ARB air locker, Detroit, Powertrax Lock-Right, Auburn Gear ECTED, Auburn limited slip, Aussie Locker, Spartan, Eaton Posi, Eaton E-Locker, Tru-Trac, mini spools, and full spools.

  • The 31-spline axles also use a larger bearing than the 28-spline versions, forming a stronger assembly all around, save for the differential. Also, if you’re considering swapping in an Explorer axle, it measures 59.5 inches wide from flange to flange and has the largest axle tube size (3.25 inches) of this axle line.

  • Ford produced the 8.8-inch axles with 28- and 31-spline shafts. These were mixed and matched in the various vehicles with the 31-spline versions typically ending up in the heavier vehicles with bigger engines.

  • One downside to some of the newer axles is a weakness in the housing assembly where the axletubes enter the differential housing. Ford secured each tube to the housing with three steel rivets, pinning the tubes in place. Harder use may spin these tubes in the housing. The common solution is to run a circumferential weld at this joint.

  • If you’re running stock axleshafts, especially old ones with a lot of miles, a good upgrade is to swap in aftermarket chromoly shafts. These will increase your axle strength for relatively low cost, and are a simple bolt-in alternative when you don’t need the jump in strength provided by a full axle swap.

  • Stop the C-clip axle retention by installing a C-clip eliminator kit. Strange Engineering has developed a kit that rids the Ford 8.8 of its C-clip weakness and uses a set of pressed bearing hub assemblies at the axle ends. Superior Axle & Gear also offers its Super 88 kit for 1996 and newer Explorer and Mercury Mountaineer disc brake axles. It’s a complete C-clip eliminator kit with chromoly axleshafts.

  • Yukon offers a Ford 8.8 disc brake conversion kit if you’re looking to upgrade a drum brake axle to a more robust braking setup. An additional advantage to running a disc brake conversion with a C-clip axle is that the rotor and caliper usually retains the axleshaft in the housing should a C-clip assembly fail.

  • The factory differential cover is made from a thin sheetmetal stamping or fiberglass and is vulnerable to denting or tearing when used off-road. G2 Axle & Gear and other manufacturers make heavy-duty covers able to dissipate heat quicker and better withstand a beating in the dirt. These covers are less prone to developing leaks from severe use.

  • Many Ford 8.8 axle pinions use a flange to mate to the driveshaft, instead of a yoke. Some variations exist in flanges across the axle model years. If you’re swapping axles, it’s fairly easy to find the adapter pieces to convert from one to another or employ a driveshaft shop to modify whatever mating ends are needed. 1310 (early years) and 1330 series joints are fairly common with these axles. Aftermarket yokes can also bump the joint size up to the heavy-duty 1350 series.