Michael Johnson
Technical Editor
March 1, 2000

Step By Step

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Jay Meagher of LaMotta's Performance in Longwood, Florida, was more than happy to help us with our 8.8 buildup. Too happy, we think. We were pleasantly surprised, though. Jay actually took a shower the morning of our shoot, and it wasn't even Saturday yet. All kidding aside, Jay handled the installation easily, and if not for the axle issues he would have had us back on the road in a couple hours.
Jay removed the tires and our Kenny Brown Panhard bar to gain access to the rearend cover. He then loosened the driveshaft bolts and tucked it out of the way. Be sure to mark where the driveshaft is positioned on the flange so you can put it back in the same spot upon reinstallation. This is done to maintain the proper balance of the driveshaft assembly.
Loosen the rearend cover and drain the fluid. Jay leaves the top bolt in slightly to regulate the flow of the used fluid.
This retaining bolt holds the carrier pin in place. Once the bolt is removed, take out the carrier pin. Jay then uses a screwdriver and pushes the axles inward to remove the factory C-clips so the axles can be taken out.
Once the C-clips are removed, we can take out the stock axles. Ours looked pretty good except for a few pits found on the driver-side axle.
Jay makes a mark on the bearing caps to make sure he reinstalls them on the same side as they were put in from the factory.
After the bearing caps have been removed, a large screwdriver is used to pry the old differential out.
To remove the old pinion, loosen the pinion nut and driveshaft flange. Then, using a hammer, knock the pinion free so it can be taken out.
Remove the pinion and use a razor blade to scrape silicone off the mounting surface.
With the rearend case empty, the inner and outer pinion bearing races must be removed. Jay uses a hammer and punch to take them out. Once the races are removed, thoroughly clean the case with brake cleaner or equivalent.
While the case is drying out, Jay begins cleaning the rearend cover and other parts that will be reinstalled.
Beginning the reinstallation, Jay lightly taps the new bearing races into place, along with the outer pinion seal. We also got a complete rearend bearing and seal kit from National Drivetrain, which had everything we needed to do the install.
Jay uses this pinion depth gauge to figure out what size pinion shim is to be used for the ring-and-pinion setup. This is done to make sure the ring and pinion mesh together properly, with no gear whine. The shim we're measuring for goes between the pinion and pinion bearing.
National Drivetrain had an FRPP Traction-Lok unit and 3.55 gears in stock, and also sent along a bearing and seal kit. We initially got our axles from National Drivetrain, but they had the wrong bolt pattern. To its credit, National Drivetrain was out of stock on 31-splines when we ordered our parts and scurried to get us the axles as soon as it could. However, we had to get Moser 31-spline axles, courtesy of Central Florida Motorsports, in order to complete the installation under our time constraints.
With the proper shim size found, the pinion bearing is pressed on and the pinion is installed in the differential case. Remove the play on the crush collar and continue to tighten the pinion nut until you yield 10 inch-pounds.
With the pinion in place and the driveshaft bolted back in, Jay gets our new FRPP Traction-Lok unit ready to install. The ring has been torqued 75 lb-ft. Jay installs the new bearings on the Traction-Lok unit.
With the appropriate carrier shims in hand, the differential is set in place. It took Jay a couple tries to get the proper shim size, but that's standard procedure when swapping gears. This is another method used to tune in the backlash.
A dial indicator is used to check backlash, which is the space between the ring gear and pinion. Ford spec is 5-10 thousandths backlash. Thank's to Jay's careful installation, we have zero gear whine.
With the Traction-Lok unit ready to go, Jay installs the outer bearing and seal on each side of the axlehousing.
With the axles in place, the C-clips are reinstalled along with the new carrier pin. Since our car sees only occasional dragstrip duty, we stuck with C-clip axles. These can become a liability on high-powered cars seeing frequent dragstrip action. The old carrier pin is used to tap it into place.
When sliding the axles in place, be careful not to damage the new seal. Don't ever let the axle hang inside the axle tube, unless you like buying new axle seals.
With everything checking out OK, the bearing caps are torqued down to 75 lb-ft. Now, install the proper speedo gear and you're ready for action. To help break in the gears, we put the car in Fourth gear and held it at 2,000 rpm for 10 minutes. This was done with the car still on the lift.
RTV silicone is applied to the rearend cover prior to reinstallation to guard against leaks. We used Amsoil rearend lube and a 4-ounce bottle of FRPP Friction Modifier.

Stepping up in the gear department has always provided discernable results. It's not one of those modifications that make you think you're accelerating faster, you are accelerating faster. We've all installed a performance component and felt our Mustang was faster, but the improvement doesn't show up on the dyno or at the track. Even though the seat-of-the-pants won't show up on the dyno, we guarantee you will feel an improvement by adding a numerically higher gear set. Your strip times will improve as well, provided you have adequate traction. If you were slippin' and slidin' down the track before you added gears, it will only get worse with more gear on board.

Our '93 LX coupe came from the factory with 3.08 gears. Though a little better than 2.73 gears that most Fox Mustangs were saddled with, we know more gear is better. We decided on 3.55 gears. We know what you're saying--sissy, whimp. Yes, we could have added 3.73s, but we thought they'd be a little much for the highway. Some people run 4.10s in their street cars, and that's fine. We do quite a bit of highway driving in our coupe and wanted to keep the revs well under 2,500 rpm while still maintaining 70-75 mph.

To help you determine what gears you need, try to drive or ride in a Mustang with 3.55s, 3.73s, and 4.10s, and decide which you like best. Each gear set falls into its own category. If you drive your Mustang every day and go to the track every couple of months, 3.55s may be the perfect gear for you. For those who drag race, yet drive on the street as well, 3.73s will probably make you giddy. We would reserve 4.10s and even 4.56 gears for those who drag race every weekend.

We chose not to stop with the gears, stepping up our '93 with stronger 31-spline axles and a new FRPP Traction-Lok unit. If you're swapping the gears in your Mustang, it would be wise for you to do the same, especially if you own a Fox-body, as the factory Traction-Lok may be on its last legs (if yours was factory equipped with one).

National Drivetrain supplied the gears ($139.95), master bearing kit ($85), and Traction-Lok ($225), and Moser supplied the 31-spline axles ($225 a pair). For the installation, we took the short trip to LaMotta Performance in Longwood, Florida. Jay Meagher was happy, perhaps a little too happy, to lend a hand (see lead photo). We also contacted Parkway Ford for the correct speedo gear ($12.95) for the 3.55s. With this installation, our 8.8 rear is ready for pretty much anything we can throw at it, especially those pesky F-bodies.