Most people know I'm a little...
Most people know I'm a little nutty about Project Vapor Trail. I don't let just anyone touch her. After a recon run over to ProFab Performance in Thonotosassa, Florida, I felt more than comfortable letting Blue Oval expert Dave Piercey wrench on PVT. Dave has been swapping gears since before I had a driver's license, so he knows a thing or two about getting them spot-on.
It's been popular to add gears to Mustangs since the dawn of time. Gears are usually one of the first performance modifications because they make an instant impact in the way the car feels. Sure the right gear makes the car quicker, but it's the seat of the pants that really makes the gear swap one of the most popular Mustang mods.
I really don't know why I waited so long. I guess I had some vague, silly concerns about noise and gas mileage. Could a 700-rwhp GT500 really need gears?
As it turns out, yes it does. Sure the car never had a problem getting out of its own way, but the addition of gears makes dealing with the GT500's naturally tricky clutch engagement much easier. Moreover, the 3.73s keep the car in the happy place of its powerband at all times, and the highway cruising speed is only up a couple hundred rpm. Ultimately, mileage seems to only have suffered marginally. Moreover, the car simply feels snappier and more responsive, and that's what it's all about.
While PVT was under the knife, it was a good time to add some complementary hardware. I opted for a diff girdle from FRPP, a Torsen T2 differential from FRPP, an aluminum driveshaft from Axle Exchange, and a driveshaft safety loop from BMR. To make it all happen, I carted the parts over to ProFab Performance, where renowned gear setup expert Dave Piercey worked his magic with a perfect, noise-free install.
Follow along with the captions to see how Dave brought PVT's driveline up to snuff with its other mods.
If you're going to swap gears,...
If you're going to swap gears, the stock Traction-Lok has to come out anyway, so it's a good time to consider swapping in a performance differential. To get the most performance from your ride, you need all the power applied to the pavement. Drag cars can simply connect both axles with a spool, but a street car like PVT needs torque biasing for all-around use. I opted for the Torsen T-2 diff (PN M-4204-T31; MSRP $589) from Ford Racing Performance Parts, which uses helical gears to constantly bias torque between the two rear axles. The Torsen is quiet enough for the street and durable enough for the FR500 race cars (in T2R form), so it's a good match for PVT.
As I mentioned, gear noise...
As I mentioned, gear noise was one threat that kept me from making the move sooner. Well, most people will tell you to go with FRPP gears if you want them quiet, and that's just what I did. I opted for the ever-popular 3.73 ratio (PN M-4209-F373N; MSRP $ $179.95). This set now benefits from a new Face Hob Process, which is said to deliver higher quality, strong gears. Combined with Dave's expert installation, mine are indeed library quiet.
When doing a gear or diff...
When doing a gear or diff swap, you might want to order this FRPP installation kit (PN M-4210-A; $162), as it includes all the necessary shims and bearings for the install, including the unique high-torque pinion bearing that is stock on Bullitts and GT500s.
A gear swap also presents...
A gear swap also presents a handy opportunity to add an axle girdle (PN M-4033-G2; MSRP $199) like this beauty from FRPP. It features a low-profile design just for S197 'Stangs, and is said to increase ring and pinion life by adding rigidity to the 8.8 rear. It also adds handy drain and fill plugs for servicing.
I warned Dave that PVT had...
I warned Dave that PVT had a few suspension upgrades that might complicate the gear and diff swap. If you are considering adding Steeda's sweet Watt's link like I did, you should definitely consider doing the gear swap beforehand. That said, its presence wasn't a big deal, it just added a bit of time to the job.
To get the party started,...
To get the party started, Dave removed the Steeda Watt's link, unbolted the factory diff cover, and popped it off with a prybar.
Next he unbolted the cumbersome...
Next he unbolted the cumbersome stock driveshaft. We did an unofficial weigh-in of the stock 'shaft and it tipped the scales at 38 pounds.
From the moment I saw the...
From the moment I saw the S197's two-piece driveshaft, I was scratching my head. It seemed like a lot of weight and complexity in the name of improving NVH. In fact, after adding the Steeda suspension to my car, the stock driveshaft actually made a tick-tock noise when I got on and off the throttle because of the innate slack of its two-piece design. Of course, weight is the enemy of performance; so dropping some reciprocating weight while adding durability is always a great idea. After doing some research, I discovered the one-piece aluminum shafts from Axle Exchange (PN MAMTCOBRAST; $739.95) have a great reputation. They are made in the USA with Alcoa 6061 T-6 aluminum, and benefit from Precison Schenck balancing.
Using this puller, Dave plucked...
Using this puller, Dave plucked off the stock pinion flange.