Jim Smart
August 22, 2014

Additional Photography by Strange Engineering

If you've been around long enough you remember a day when securing a Ford 9-inch rearend for a classic Mustang was a great challenge. You had to comb salvage yards and the classifieds to find a core and hope it was sized right for a Mustang. The hot ticket was once the Lincoln Versailles 9-inch with its disc brakes. These days, the Versailles rearend is anything but desirable because its disc brake parts are hard to come by and not that beneficial in the first place.

Strange Engineering makes it possible for you to have a completely new 9-inch Ford rearend without having to sell off the farm. We're talking centersections, third members, differentials, axles, axle tubes, and even whole axle housings built any way you desire. Strange Engineering produces Ford 9-inch housing centersections (PN H-1110) for just $258.50, which gives you a great foundation to build on using 3-inch axle tubes. Complete 9-inch axle housings are available in a variety of configurations for every Mustang generation from 1965 to 2014. Building a hot Fox body for weekend drag or road racing? Strange Engineering has the 9-inch housing for your four-link setup. Those of you building S197 cars will be pleased to know Strange has housings for your three-link suspension with and without flanges.

We're installing a complete Strange Engineering 9-inch axle assembly in the Rebuilding Generations '71 Mustang convertible with help from Bruce Couture of Modern Driveline. We sat down with Strange Engineering and came up with the S-Series 9-inch nodular iron case PRF130 with 3.55 gears, 28-spline axles, and locking clutch–style differential. You can build this iron case for your classic Mustang for $1,189.65 plus tax and shipping. There are also a number of great performance upgrades you may consider depending on what you want your Mustang to do. These include, but are not limited to: chromoly yoke, Strange Forged clutch differential, Eaton 28- or 31-spline TrueTrac or Detroit Locker differential, Strange 35-spline Strangetrac differential, and Strange black forged pinion support.

To complete your 9-inch swap, you're going to need the right driveshaft. Modern Driveline carries and can order the correct Dynotech steel or aluminum driveshaft for your 9-inch driveline swap.

01. The Rebuilding Generations/Optima Battery ’71 Mustang convertible project has been an opportunity for the young and advanced in age to work together to achieve a common goal. Not only do older folks with a lot of experience get to teach young people, young people have the opportunity to share new information with those their senior to where everyone wins in the game of knowledge. The Rebuilding Generations Mustang is unloaded at Modern Driveline in suburban Boise, Idaho, and place on a lift.

02. Strange Engineering has Ford 9-inch housing centersections with accommodations for 3.000-inch O.D. axle tubes. There’s the early style housing with a round pot (1957-1965) or the dimpled/bulge 1967-up. Look at the generous welding going on here long on strength and leak resistance.

03. This is Strange’s 9-inch S-series Nodular Iron (PN PRF130) case built any way you desire. Our 9-inch chunk is a clutch-style locking differential with 3.55:1 gears, which will be mated to a Modern Driveline Tremec T-5 five-speed. In overdrive at 70 mph, the Rebuilding Generations 302ci engine will be spinning at 2,000 rpm. The S-Series iron case is much stronger than Ford’s original case and can withstand a lot of power. There is also the Strange “Pro Nodular” waffle cast iron case for $100 more.

04. If you want to reduce weight and still have the benefit of strength, check out Strange’s family of aluminum differential cases, including the Pro HD (PRF180), L/W (PRF170P), and lightweight aluminum case (PRF170, shown).

05. For $324, plus tax and shipping, you can score new Strange 28- or 31-spline axle shafts for your Ford 9-inch axle package. If you’re rebuilding a Ford 8-inch, opt for 28-spline Strange axles.

06. If you’re working with a blank sheet of paper and want to build a Strange 9-inch axle assembly from scratch, you can work closely with its technical and sales staff to build a drop in axle package you can install in a couple of hours. This is the Strange 9-inch for Fox and SN-95 four-link rear suspension systems. However, you can spec one up for your classic leaf spring or S197 three-link.

07. Strange Engineering shipped us this complete 9-inch S Series nodular iron assembly complete with locking feature and 3.55:1 gears for a sweet combination of daily commute and hot weekend fun.

08. Bruce Couture of Modern Driveline explains the fundamentals of a driveline swap to members of Rebuilding Generations. This isn’t just about a rear axle swap, but how to get driveshaft and pinion angle right when you’re swapping in a new rear axle.

09. First, the existing 8-inch Ford rear axle is properly supported and all connections separated. Here, the rear brake hose clip is removed and hose disconnected. Brake fluid must be collected and properly recycled.

10. Rear shock absorbers are disconnected top and bottom using a 9⁄16-inch deep well socket. The shocks can be recycled as well, offsetting some of your new hardware purchase.

11. Parking brake cable routing and connections are carefully documented for proper installation later, then, disconnected as shown using a ½-inch deep well socket and open-end wrench.

12.The Rebuilding Generations crew rallies around to get our Strange 9-inch axle into position. Note the rich satin black powdercoating, which is a worthwhile option for less than $100 more and will last the life of the axle. Couture has carefully chained the axle housing to a transmission jack and we’re good to go.

13. TCP five-leaf springs and adjustable VariShocks have been installed. Spring pads are aligned with dowel pins for proper axle alignment.

14. U-bolt fine-thread nuts are snugged uniformly, but not tightened. Although very few of us do this, Couture suggests the use of a torque wrench on rear axle U-bolts to prevent axle tube distortion.

15. Depending upon the axle housing you’ve ordered from Strange Engineering you can have as many as two filler options. This is the filler port located in the differential housing like you will find in a stock Ford casting. The plug accepts a 3⁄8-inch extension. The differential is filled here to the spillover point.

16. This is the Strange 9-inch housing with a quick-fill housing. We’re using the quick-fill yet using the casting fill as a fill reference. When lube begins to flow out of the differential casting fill, we are full. Because we have a clutch-style positive traction differential, we also need a friction enhancer for clutch engagement. Ford’s CM-19546-A1 Friction Modifier in the 3.8-ounce bottle gets the job done. Mix it in with Lucas 85W-140 gear lube.

17. Modern Driveline provided Rebuilding Generations with a choice of either a steel or aluminum driveshaft engineered for this ’71 Mustang application with a small-block, T-5 transmission, and the 9-inch Strange axle. Shown here is a late-model shaft for Fox, SN-95 and S197 Mustangs. One-piece driveshaft conversions are available for S197 Mustangs from Modern Driveline.