KJ Jones
July 25, 2007

Horse Sense: GTR High Performance experienced an unfortunate setback on July 4, 2006, one day before our scheduled clutch installation. One or several lowlifes broke into GTR's showroom and made off with computers that contained the company's critical business records. We believe someone in the SoCal 'Stang community might know something about this caper, so we hope somebody will provide information that might help the Topete brothers recover their PCs or the valuable data that was stored on them. Call Rick or Gonzalo at (909) 987-4386 if you can help solve the mystery.

If we asked 'Stangbangers to name their favorite transmission, we bet the unanimous response would be manual because most people believe those types of 'Stangs are more fun to drive.

We've provided information covering manual-transmission upgrades for 5.0 and 4.6 Mustangs (see "Rock the Gearbox," Dec. '05, p. 134, and "Top Gear," Sept. '06, p. 124), it's been awhile since we've filled you in on clutch technology for stick shift gearboxes.

Advanced Clutch Technology of Lancaster, California, has been in the high-performance arena for more than 10 years, so we can't say the company is new to the game. In that decade, ACT's focus has been on the sport-compact market, so we were surprised to see its display at the NMRA's season opener in Bradenton, Florida. Sales Manager Daryl Sampson told Editor Turner about ACT's initial foray into the Mustang world-and what a foray it is.

ACT's opening act is the introduction of nine different 10.5- and 11-inch clutch kits for street applications. The 10.5-inch street clutch is rated at 483 lb-ft a with heavy-duty pressure plate and 573 lb-ft of torque with the Xtreme pressure plate. For full-on race-Mustang applications, ACT offers a 10.5-inch spring- or solid-hub race clutch rated at 619 lb-ft with a heavy-duty pressure plate and 733 lb-ft of torque with the Xtreme pressure plate. Eleven-inch clutch kits for '03-'04 Cobras and S197 GTs are also offered, but the torque rate is not available.

After hearing about ACT's clutch kits for late-model 'Stangs, installing one immediately became an agenda item. We went to see Ricardo and Gonzalo Topete of GTR High Performance, a 'Stang facility in Rancho Cucamonga, California, to ask for their help in locating a car and performing the clutch swap.

We followed Rick and GTR tech Chris Balster as they removed a worn-out stock-style clutch and replaced it with ACT's Heavy-Duty Street Kit for '86-'92 Mustangs (PN FM1-HDSS; $418.83) on a '91 GT owned by Caesar Diaz.

We performed the clutch job on Caesar Diaz's clean '91 GT. Once the car is safely racked, Chris Balster gets things started by removing the exhaust system. Of course, the negative battery cable was disconnected prior to lifting the car. Wiring for both O2 sensors must be disconnected before the H-pipe can be taken down. Do-it-yourselfers should keep that in mind because the H-pipe or catalytic converters sometimes need to be wrestled out. Forgetting to unplug the sensors can possibly lead to wiring damage that will be difficult to repair.




The old clutch/pressure plate assembly is removed and discarded.





When you're doing this type of project, making a reference index on the driveshaft and the diff flange is like leaving a trail to find your way home. When it's time to reassemble the drivetrain, simply align the two marks and bolt down the shaft. This ensures that the driveshaft is reinstalled in its original position and lessens the potential of throwing off the drivetrain's overall balance.


Once everything is removed from the transmission case, Rick and Chris move the T5 away from the engine and lower it with a transmission jack. We suggest that first-timers make labels using masking tape and a marker to help identify the reconnections that must be made on the tranny. Everything here is straightforward. With the car raised high enough on jackstands, this clutch-swap project can be done in the garage or driveway. A twin-post hoist makes things easier and quicker, but that doesn't mean a clutch job is impossible to do at home.



The flywheel contains three small steel pins that are used for mounting the pressure plate. These pins must be removed before it's sent off for resurfacing or for use in a new replacement.





A spare transmission yoke makes a great plug for the transmission's output shaft. It's not uncommon for a tranny to leak fluid from this area when the driveshaft is removed, so make sure you have something that can be used as a plug.



The flywheel in Caesar's 'Stang was in bad shape with heat spots and cracks in its surface, but it wasn't beyond saving. Excessive cracking can cause the flywheel to come apart or explode. We sent the plate to a local machine shop for resurfacing and it came back looking fresh and new. Unlike brake rotors, there's no minimum thickness for a flywheel's surface, so putting a new face on a worn wheel can be done again and again. Flywheels that have been cut several times must finally be replaced when more material than usual has to be taken off in order to achieve a smooth surface. ACT is currently developing its own flywheels for Mustang-clutch applications that should be available by the time you read this.




Once everything has been cleaned, Rick lubes all of the clutch-related mechanical hardware-such as the throw-out bearing, bearing retainer, input shaft, clutch fork, and pivot ball-before they're reinstalled.




This is ACT's 10.5-inch clutch kit for 5.0 Mustangs (PN FM1HDSS; $418.83). The complete package includes a disc (PN 3001005), a heavy-duty pressure plate (PN F013), a release bearing (PN RB174), and a pilot bearing (PN PB1019).





Chris uses a slide hammer with a fixture at the end that grabs the pilot bearing and pulls it backward with enough force to extract it from the crankshaft.







Chris positions the freshened flywheel. Flywheels (and flexplates for AODs) have a specific bolt pattern, so it's important to make sure the bolt holes are properly aligned with the plate before attempting to secure it. Before installing the clutch, the flywheel should be cleaned with a good dosage of brake cleaner to remove any fingerprints or debris from the surface.












The new ACT clutch (left) measures 0.358-inch thickness and the original disc is worn down to 0.281 inch. The difference in the feel of the pedal and overall smoothness is quite noticeable.








Cleaning parts (in this case, the block protector) is one of the tasks that must be performed when replacing a clutch. We recommend also doing some preventative maintenance/repairs, such as replacing the rear-main seal if it's leaking. Leaking is usually a problem of an older 5.0.










An alignment tool (PN ATFC10) is included with the ACT clutch kit. This makes it easier for Chris to match the splines in the clutch disc with those on the input shaft of the transmission. The pressure plate is usually shipped with a thin film of oil on the surface, which protects it from rust. Spraying the plate with brake cleaner is a good idea.



Once the clutch assembly is installed, Rick and Chris raise Caesar's T5 back into the transmission tunnel and bolt it to the engine. Flywheel bolts are torqued to 75 lb-ft and pressure plate bolts are torqued to 35 lb-ft. A few drops of blue Loctite help ensure the bolts stay secure.







Once the transmission is back in place, completing the clutch job is simply a matter of reconnecting the wiring harnesses and hard parts such as the driveshaft, exhaust, and starter, then bringing the car back down. When the clutch cable is reinstalled, don't forget to snap the retainer clip back into place. The cable is basically the clutch's linkage and it operates the clutch fork. A non-functioning clutch can leave you stranded if the cable ever becomes dislodged.










Taking care of the interior items is one of the final steps of a clutch-swap. Rick reinstalls Caesar's shifter and center console, and properly adjusts the clutch cable by repetitively pumping the pedal a few times, pushing it down, and using his toe to pull it back up.





A road test is the final step. Putting a few easy miles on a new clutch helps seat it. Rick says the ACT clutch is smooth and requires little pedal effort as it engages about an inch and a half from the floor, and it doesn't seem to have the chatter or choppiness that he's experienced with other clutches GTR has installed.



WhAT'S WEAR?
Below are examples of wear that affects clutch parts over time, miles, and hard driving.



Disc: Friction material deteriorates, which usually is a result of the disc and flywheel spinning at different speeds instead of in unison. This is caused by slipping the clutch. The disc can also incur damage when oil from a 5.0's leaking rear main seal or a T5's input seal contaminates the surface.



Fly wheel: Cracks, hot spots, or warpage hinders the adhesion capability of the disc. This is caused by excessive heat and aggressive driving.






Clutch release bearing (throw-out bearing): Another problem sometimes associated with clutches is a worn throw-out bearing. This problem is often characterized by a rumbling noise when the clutch engages.




Clutch-release-bearing retainer (aluminum): It develops a rough groove over time along the area the bearing slides over. This is caused by excessive engagement/disengagement of the clutch, riding the clutch, poor clutch alignment, and heat. This part is usually replaced by a steel piece that is more durable.