This is the new carbon rebuild...
This is the new carbon rebuild kit for the 8.8-inch Traction-Lok limited-slip differential. It's available from Ford Racing Performance Parts (PN M-4700-C). The guys at FRPP recommended this kit for improved durability, especially in high-horsepower and racing applications.
Horse Sense: This project focuses on removing the differential for the purpose of rebuilding the Traction-Lok. It's also a great time to replace the bearings and seals in the rear axle and even swap gears. The rear brakes will be removed, so check to see if they need some freshening up.
With supercharged '03 and '04 Cobras prowling the streets, someone at Ford must have figured that the usual Traction-Lok limited-slip differentials weren't going to last. If you own a used Mustang, you may already know it doesn't take 390 hp to wear out a Traction-Lok, especially if your car has some miles on it or you do any racing. The good news is, whatever Mustang you have, you can upgrade it with these new, more durable carbon-fiber friction plates from Ford Racing Performance Parts.
Rebuilding the Traction-Lok isn't difficult, but when you factor in the removal and reinstallation of the differential, the job becomes considerably more intimidating. Truth be told, we couldn't have done it ourselves. You'll notice a few expensive, not-so-common tools in the following how-to photos, which all belong to Dan at DB Performance. We followed along with the camera as he did the dirty work. Dan has rebuilt quite a few Traction-Loks, so he was curious to see the new carbon-fiber friction plates. The project didn't throw us any surprises, but he mentioned repeatedly how long it took because of all the photos.
When all was said and done, the freshly rebuilt Traction-Lok gave this 110,000-mile '96 Cobra a new lease on life. The car has much more traction during acceleration, especially in the rain and through the corners. You can't feel or hear it working, unlike some of the heavier-duty locking differentials out there. Despite the somewhat difficult installation, the relatively affordable price makes this a great maintenance/upgrade project for any high-horsepower or high-mileage Mustang.
This a 4.10:1 ring-and-pinion...
This a 4.10:1 ring-and-pinion set from FRPP. Gears are available from a variety of manufacturers, but the FRPP versions have a reputation of being among the quietest. From a seat-of-the-pants-per-dollar standpoint, gears rank near the top.
If you're rebuilding your Traction-Lok, it's a great time to swap in lower (numerically higher) ring-and-pinion gears. Gears are an extremely popular upgrade for good reason-they improve seat-of-the-pants sensation of acceleration. For a great gear-ratio calculator, check out The Corral Web site and forum (www.corral.net/tech/gearcalc.html). You can use this calculator or a similar one to get a preview of how life would be with a certain rearend gear.
The great thing about the Corral's calculator is it's preloaded with most late-model Mustang five-speed gear ratios and a tire-height calculator. This makes it easy to see how your Mustang performs in a given gear with a given tire size, at a given rpm, and with a given rearend gear. That sounds like a mouthful, but here's an example. For the '96 Cobra featured here, the owner wanted an aggressive gear for getting out of the hole, but he was worried about driving at a high rpm for a long commute. He intends to cruise at 75 mph, so we can use the calculator to determine what rpm each rearend gear ratio puts him at in Fifth gear, and choose based on the desired cruising rpm.
This project doesn't begin...
This project doesn't begin at the rearend cover, but rather by removing the rear wheels. Unbolt the brake calipers and caliper brackets and pound the rotors loose. Inspecting/repairing the brake hardware is a good idea at this time. Dan noticed that one of the caliper brackets was cracked.
For example, he's running 275/40-17s, he cruises with his T45 in Fifth gear, he wants to go 75 mph, and his stock rearend gears are 3.27:1. According to the calculator, the engine would be at only 2,150 rpm, which is great for fuel economy. Keeping all the variables the same and swapping in 3.73 gears would bump up the cruising rpm to 2,455, which is still easy to stomach with the high-revving Four-Valve engine. A few taps on the keyboard reveals that 4.30 gears, which come highly recommended from The Corral's SVT & DOHC forum members, put the cruising rpm at 2,830. The owner of this Cobra compromised and went for 4.10s so he could cruise at 2,699 rpm. With a 5.0 Mustang or even a Two-Valve 4.6, you may be less enthusiastic about cruising at 2,700 rpm. If that's the case, go for the 3.73s or 3.55s. The Corral calculator has all the transmission ratios for the T5, T45, and even the Tremec 3550.
Hard-core drag racers use a different criteria for choosing the ideal gear: their target rpm and speed through the traps at the strip. Most cars trapping more than 100 mph at the strip are comfortably into Fourth gear at the high end of the track. If the above Cobra traps at 105 mph, the 4.10s would have it running through the traps at 5,639 rpm.This isn't terrible, but it's below the engine's power peak. A set of 4.56s put the car at 6,272 rpm through the traps, assuming the speed is constant, which probably wouldn't be the case considering the new gears. Often the lower gears drop the trap speed but also lower the e.t., assuming you've got the traction. For this reason, choosing gears for a drag car is a trial-and-error process. There's also tire size to consider. The same 4.56s with a set of 275/60-15-inch drag radials bring the trap rpm back down to 5,750. Don't fear the gear!