Ford 8.8 Inch Rear End - Eight-Point Great

As you see in this photo, the bar that represents the axles is not centered inside the axle tube,which means the rearend housing isn't straight. That's not a huge problem. The heat from welding the axle tubes to the differential housing for strength and to prevent them from twisting actually loosens the metal of the axle tubes.

As the metal cools, the bar works as a guide for the tubes to set up in a new position-which isn't perfect, but it's a lot closer to straight. It's interesting to watch the axle tubes move ever so slowly into their straight positions off the differential housing.

Robert says that out of the hundreds of rears he's checked for trueness, he's only encountered two that didn't have issues.

On the left is our new "big-bearing" setup that's pressed onto the Strange Engineering 31-spline S/S Street axle compared with the stock housing end and bearing we removed. It isn't hard to see the huge difference in diameter. The big bearing has an overall journal area of 1.563 inches that can absorb a much greater load than the stocker, which measures only 1.400. When assembling axles, always install the seals first, then the bearings, followed by small, steel locking rings called wedding bands that secure the bearings and seals on each axle. The inner and outer races are incorporated with the bearings.

After installing the bearing races, then the pinion bearing and seal, an OTC pinion-depth gauge is used to determine how deep inside the differential housing the pinion gear should be installed. The tube part of the gauge is secured in the carrier-bearing journals and simulates what would be "perfect center" for the axles and ring gear. Shims with thicknesses ranging from 0.001 to 0.050 inch are placed between the tube and depth gauge-that serves as a reference for what would be the actual head of the pinion gear-until a snug fit or drag is achieved.

This is similar to checking valve clearance or gapping spark plugs. The shim size (ours is 0.031 inch) sets the pinion depth required for optimal mating of the ring-and-pinion gears. Once the pinion gear is positioned and the flange has been threaded outside the housing, a pinion nut is gradually tightened against the crush sleeve until all of the back-and-forth play has been eliminated. At this point, Robert sets preload on the pinion bearings at 20 in-lb, which keeps the pinion gear properly secured and eliminates side-to-side/back-and-forth movement without being too tight, which could cause the gears to bind.

Using a vise and rags to prevent any damage, Robert installs the Motive ring gear on Eaton's Detroit Truetrac limited-slip differential. Red Loctite is recommended for all of the bolts used for this procedure. The bolts, which are included with the ring-and-pinion set, should be tightened to 70 lb-ft of torque.

Once the carrier bearings and races have been pressed onto each end of the new Eaton Detroit Truetrac differential, Robert places the assembly into the differential housing. Setting the diff is a trial-and-error process, as the unit requires side shims of correct thickness before it can be final-installed. The side shims help determine the amount of backlash and preload to absorb side-to-side movement on the ring gear. Our housing was originally bare and did not have a differential or shims of any size to use as reference. While it's rare that the exact same-size shims (side- or pinion) will be used in a new assembly, it's helpful to have the old ones to use as a ballpark size. This is another good reason to ask someone who knows what he's doing to help. Robert has done a countless number of rearend builds, so it didn't take long for him to set up our rear with the correct shims. Final torque for the carrier-bearing cap studs and nuts is 75 lb-ft.

The backlash is the amount of clearance between the pinion and ring gears. Spec backlash for an 8.8, and the 3.73 gears is between 0.008 and 0.015 inch. Robert positions a dial indicator on the gearset and calibrates backlash at 0.010 inch, which is perfect for our setup. Setting backlash properly may have you adding shims to either side of the carrier to move the ring gear either closer or farther away from the pinion. Ring-gear runout is also verified at this time. Ours is 0.004 inch, which is about the maximum spec. It's critical to be accurate with backlash and runout measurements. The differential assembly may have to be removed and reinstalled several times to get it right, but it's the only way to accomplish this type of build without experiencing driveability problems with the rearend.

NHRA Tech rules require hardened, long wheel studs be installed on any vehicle equipped with aftermarket racing axles. This is a safety concern and we think it's a good one. We're using the 11/42-inch thread-in studs that are included with the Strange S/S Street axle package. Red Loctite is added on all of the bolts prior to tightening them down at 100 lb-ft of torque. Strange also offers 51/48-inch studs, but using the thicker lugs may require drilling the bolt holes in your wheels in order to mount them on the car. For those 'Stangbangers who are getting into a five-lug setup for the first time with this upgrade, the selection of wheel styles is insane!