ACT Chevy Camaro/Corvette LS1/LS2/LS3/LS6/LS7 Mod-Twin 10.5 XX Sprung Disc Street Clutch Kit

A cammed LS1 Camaro, a supercharged C6 or a boosted LS3 Camaro SS can make far more torque than a single disc street clutch will hold without turning the pedal into a leg press. ACT T3SS-G13 is the Mod-Twin 10.5 XX Sprung Street kit for GM LS cars: two 10.5 inch organic street discs on a sprung hub, a MaXX Xtreme pressure plate and a CNC-machined flywheel, rated by ACT at 1,169 ft-lb at the crank. It covers C5 and C6 Corvettes, 1998-2002 F-bodies, the GTO and 2010-2015 Camaros, and it is meant for big-power street cars that still see traffic.

What the Mod-Twin 10.5 XX does in an LS car

ACT's Mod-Twin doubles friction area by running two steel-backed organic friction plates with a floater between them. Both plates drive one sprung Mono-Drive hub instead of each disc carrying its own spring pack. That hub absorbs torsional vibration, which ACT says extends input shaft life and reduces driveline shock, and it lets organic street friction hold torque that would normally call for ceramic. The MaXX Xtreme pressure plate sits under a forged aluminum cover; ACT rates the kit at 198 percent over the original equipment clutch. ACT describes the feel as soft, progressive engagement with increased pedal effort and OE to mild gear noise, recommended for street or street/strip. Mod-Twin is modular and rebuildable, and replacement discs are sold separately.

Symptoms that point to this kit

• RPM flare on wide-open shifts after heads, cam, nitrous or a blower
• Slip in third or fourth that gets worse as the clutch heats up
• A single disc upgrade that held but chattered, grabbed or wore out quickly on the street
• Glazed disc or heat-checked flywheel at the last clutch job
• Burnt smell after a few passes or a road course session

How to confirm before you buy

Do a fourth-gear slip test from about 30 mph at full throttle and compare tach rise to road speed. Then rule out the hydraulics. These cars use a concentric slave inside the bellhousing, and a weeping slave or a pedal that sinks can stop the clutch from releasing or clamping fully. Our T56 concentric slave cylinder page lists the warning signs for F-body T56 cars, and the slipping diagnosis guide covers how to tell clutch slip from other driveline faults.

Fitment

ACT lists T3SS-G13 for the 1997-2004 C5 Corvette (including the LS6 Z06), 1998-2002 Camaro Z28 and SS and Firebird Formula and Trans Am, 2004-2006 Pontiac GTO, 2005-2013 C6 Corvette (LS2, LS3, LS7 Z06, Grand Sport and 427), 2010-2015 Camaro SS with the LS3, and the 2014-2015 Camaro Z/28 with the LS7. It uses a 1-1/8 inch input shaft spline. Fitment is for manual cars only. Swapped engines, aftermarket bellhousings and non-original gearboxes need a check, so send us your year, VIN and transmission before ordering. If you would rather run a different twin, compare the ACT T1S-G01 twin disc for the C5 or the Clutch Masters FX1000 for the LS1 Camaro. All clutches are in our rebuild kits category.

Install notes

• The kit includes the flywheel, release bearing, alignment tool and a pilot bearing where the application needs one. Use the new pilot bearing; an old one is a common source of noise.
• Inspect the concentric slave and clutch line while the gearbox is out, and replace a weeping slave rather than reusing it.
• Check the rear main seal. Oil on organic friction causes slip and chatter on a brand-new twin.
• Torque the flywheel and pressure plate bolts to ACT's instruction values, pressure plate bolts in a star pattern.
• Expect pedal effort 50-80 percent above stock, the range ACT gives for its Xtreme plates.
• Break in for 300-500 miles of mild stop-and-go driving before hard launches, as ACT recommends for organic discs.

Which cars does T3SS-G13 fit?

ACT lists 1997-2004 C5 Corvette, 1998-2002 Camaro Z28/SS and Firebird Formula/Trans Am, 2004-2006 GTO, 2005-2013 C6 Corvette including Z06 and Grand Sport, 2010-2015 Camaro SS and 2014-2015 Camaro Z/28, all with manual transmissions.

How much torque does it hold?

ACT rates the Mod-Twin 10.5 XX Sprung Street kit at 1,169 ft-lb measured at the crank, which ACT puts at 198 percent over the original clutch.

Is the pedal heavy?

ACT says its Xtreme pressure plates typically raise pedal effort 50-80 percent over stock, depending on the car. Engagement is described as soft and progressive.

Is a flywheel included?

Yes. The kit includes a CNC-machined, balanced flywheel, pressure plate cover, diaphragm spring, friction plates, sprung Mono-Drive hub, floater, release bearing, alignment tool and a pilot bearing where applicable.

What should I replace with it?

Inspect or replace the concentric slave cylinder, check the clutch line and rear main seal, and refill the gearbox with the fluid GM specifies for your transmission.

• Transmission Slipping Diagnosis Guide
• Automatic vs. Manual Transmission Repair Cost: What to Actually Expect
• Rebuild vs Replace vs Reman Transmission