Ford 9-Inch Rear Axle - Drivetrain Tech: Number Nine

Bill uses a good old-fashioned beam torque wrench for extreme accuracy. Torque ring gear fasteners in a criss-cross fashion, observing ring gear security and fit in the process.

Bearing cap contact surfaces should be dressed to perfect smoothness. Bolt-hole and bolt threads should be chased and cleaned for torque reading accuracy. Bolt threads should be lubricated with SAE 30 weight oil. Before torquing bearing caps, screw in bearing retainers so they just touch the bearing cups.

Use a dial indicator to show gear backlash or play - that slop between ring and pinion gears. Too much can cause excessive wear and noise and too little will cause binding and failure as the gears expand with heat. You must follow factory specifications.

Bill Thomas uses yellow grease to view gear contact patterns. You can also use white lithium grease. After checking backlash, aggressively run the gears back and forth to observe tooth contact patterns. Teeth should be smack in the middle of one another as shown. Not too deep and not too shallow.

This is the Strange 2014T-6 Lightweight Aluminum 9-inch assembly for classic Mustangs. There are two basic castings available - N1901 with a 3.0625-inch bearing bore or the N1904 with a 3.250-inch bore. This is more for racing because, due to the flexible nature of aluminum, gear life isn't as long. If you want less weight and superior casting strength, this is a terrific choice.

A close-up view shows the real strength in a Strange 2014T-6 aluminum casting-a cross-web design designed to take punishment.

Do you see how much meat Strange puts around the pinion pilot bearing? Whether you choose aluminum or nodular iron, you're getting a better casting.

Your weight loss program can also include the lightweight aluminum pinion support from Strange, available from Bill Thomas Enterprises.

Most 9-inch axle assemblies have the same 28-spline axles found in 8-inch housings. Most street applications will do fine with 28-spline axles.

If you're going to step up the power to 350 and beyond, you're going to need 31- or 35-spline axles and hubs. There's even a 40-spline axle/hub available for extreme duty service. We've worked closely with Mark Williams Enterprises, which produces heavy-duty Master Line axles and bearings for high-performance applications.

Although your Mustang was originally fitted with sealed axle bearings, the trend today is more toward open bearings lubricated by axle lube. This is quite common with late-model Mustangs with 8.8-inch rear ends.