Lethal Performance's own parts line started with catted and off-road stainless midpipes for late-model Mustangs, and those did well enough that we kept going. The first piece of our clutch and flywheel line was this one: the Lethal Performance Lightened Steel Flywheel. It has since become the flywheel inside our LPX and LPXHD twin-disc kits and the base of every combo package we sell. Here is what it is and why we keep bolting it to our own cars.
Why Lightened Steel
A flywheel has two jobs that pull in opposite directions. Less mass means less parasitic loss, so the engine revs quicker and more of what it makes reaches the tires. More mass means more stored energy, so the RPM does not fall out of the powerband between shifts and the car is easier to launch and easier to drive in traffic.
At 19.4 pounds, the lightened steel flywheel sits in the middle on purpose. It is lighter than a stock or standard steel flywheel, which cuts the parasitic loss, but it keeps enough rotational mass that you do not get the aluminum-flywheel RPM drop between gears. For a street/strip car that has to launch hard and still idle through a parking lot, that is the right trade, and it is why we have run one in nearly every manual Lethal project car.
Specs and Features
- Construction: lightened steel, 19.4 lbs
- Bolt pattern: 8-bolt main
- Ring gear: 164 tooth
- Balance: 0 oz, neutral
- Certification: SFI certified
Steel construction. Steel gives the flywheel the strength to take repeated hard launches without distorting, and the 164-tooth ring gear and neutral balance match the factory setup, so the starter and the engine see what they expect. Steel is the right call anywhere off-the-line acceleration matters.
SFI certified. Stock cast flywheels have been known to come apart at high RPM, and a flywheel failure is not a repair bill, it is a trip to the hospital. SFI certification is what lets you run at a track or strip that checks for it, and it is cheap peace of mind in a daily driver.
SFI certified
Fitment
The LP-854 fits every Mustang with an 8-bolt crank flange: the 1999 to mid-2001 GT (production date through 06/01), the 1996-2004 Cobra, the 2003-2004 Mach 1, the 2007-2009 Shelby GT500, the 2011-2017 GT, and the 2012-2013 Boss 302.
Clutch and Flywheel Combo Kits
The flywheel is in stock on its own, and it is also packaged with the clutches we sell the most of, matched by input shaft spline count. Buy the combo and the two parts arrive together, already a known-good pairing.
10 spline: mid-2001 to 2010 GT and Bullitt, 1999-2004 Cobra and Mach 1
26 spline: 1996-2004 Cobra, 1999 to mid-2001 GT, 2007-2009 Shelby GT500
23 spline: 2011-2017 Mustang GT, 2012-2013 Boss 302
Want the flywheel with one of our own twin-disc clutches instead? Every LPX and LPXHD lightweight steel flywheel kit ships with it in the box.
Frequently Asked Questions
Steel or aluminum flywheel for a street Mustang?
Lightened steel for a street/strip car. It cuts parasitic loss against a stock flywheel but keeps enough mass that the RPM does not drop out of the powerband between shifts. Aluminum revs faster and gives up that stored energy, which is why we only pair aluminum with the 2018 and newer twin-disc kits where it keeps the weight near stock.
How much does the Lethal Performance lightened steel flywheel weigh?
19.4 pounds.
Is the Lethal Performance flywheel SFI certified?
Yes. Most tracks and strips require an SFI-certified flywheel once a car runs quick enough, and it protects you in a daily driver as well.
Does it fit a 2005-2010 Mustang GT?
No. Those cars use a 6-bolt crank. The LP-854 is an 8-bolt flywheel for the 1999 to mid-2001 GT, 1996-2004 Cobra, 2003-2004 Mach 1, 2007-2009 GT500, 2011-2017 GT, and 2012-2013 Boss 302.
Does the flywheel come with the clutch?
On its own it is just the flywheel. The combo kits above pair it with a McLeod RST, McLeod RXT, or Lethal Performance Street Warrior clutch, and every LPX and LPXHD lightweight steel kit includes it.
In Stock, Ready to Ship
The flywheel on its own, or paired with the clutch that matches your car. Questions? Give us a shout. #teamlethal
