Project Box Hauler – Clutch Upgrade

July 18th, 2010

By: Kevin Wilson

Photos: Kevin Wilson

Doing a clutch R&R on a diesel is not usually something you can accomplish in a driveway. With well over 200,000 miles of hard towing duty, Project Box Hauler was overdue for a clutch system overhaul.

Driving Force
EZ Clutch Upgrade for Project Box Hauler

Anyone who has ever owned a manual transmission vehicle knows how important the clutch is. It is the vital connection between the engine and the driveline, and is responsible for turning the engine’s torque and horsepower into usable forward motion. When things are right, the clutch assembly provides easy gear changes and plenty of clamping force for day-to-day driving and towing.

On the other hand, when things are wrong with the clutch assembly, a whole host of problems can arise due to simple clutch slippage from a maladjusted clutch pedal linkage, to clutch chatter, vibration and other maladies like a broken pressure plate diaphragm, cracked clutch plate and throw-out bearing failure—not pretty and usually expensive to diagnose and fix.

Which Clutch Is Best for Me?
For diesel owners with manual transmissions, it’s even more important to have a properly working clutch, since most turbo diesels can crank out over 500 lb-ft of torque at the flywheel, and that’s before you turn up the wick with a tuner, exhaust and programmer. Getting the proper clamping force to handle that torque load is essential, especially if you plan on attaching a 10,000-plus–pound trailer to the back of the truck. Sure, the stock clutch will work fine for a while, but since all clutches eventually wear out, the question becomes, “What do I replace it with?”

Diesel owners have a lot of options out there, from a stock replacement all the way up to King Kong sled pulling clutches. So you have to be honest with yourself about how you use your truck, what modifications have been done to up the power, and how much weight you intended to tow for how long. Also, if your truck is a daily driver, you want to work the clutch in stop-and-go traffic without having the left leg of a bodybuilder to do so.

The setup we selected for the truck is the new Centerforce DFX clutch assembly specifically for ’99-to-’04 Ford Super Duty pickups with the 7.3L Power Stroke. The system comes complete with the clutch, pressure plate, flywheel, throw-out bearing, alignment tool, and a pilot bearing already installed in the flywheel.

Our Project Box Hauler, the high-miler ’01 Super Duty, was the perfect candidate for a new clutch. With 200,000-plus miles on the clock, nearly all of which were towing duty, the Ford had been used and abused, and the clutch was showing signs of failure. The clutch pedal was as stiff as steel, even though it was hydraulically actuated, indicating issues with the pressure plate. Plus, the whole drivetrain had a bit of vibration in it, another indication that something was about to let go.

The Centerforce Solution
We rolled our project pile up to H&H Diesel Performance in Dewey, Ariz., for some diagnostics, and an eventual clutch R&R. Owner John Hughes confirmed our suspicion that the clutch was junk and recommended a replacement setup from the folks at Centerforce. He also said we should replace the hydraulic clutch assembly with a stock replacement that comes sealed and pre-bled for easy installation.

The folks at Centerforce, who were just up the road in Prescott, Ariz., came down to H&H and brought their latest and greatest setup for daily-driver diesels, a DFX clutch assembly specifically designed for the 7.3L Super Duty. The DFX is Centerforce’s newest extreme performance lineup of clutch products specifically designed for diesels and high-torque applications.

The DFX utilizes Centerforce’s patented centrifugal weight system for increased holding power as the RPMs climb. Nodular iron pressure plate rings and reinforcements help prevent drive strap breakage. Centerforce claims the DFX system has 800 pounds more clamping force than the stock OE pressure plate. The DFX clutch disc features a “Spicer” type hub for added durability and strength. It also utilizes Cera-Metallic friction pads that offer smoother engagement and improved holding power over the stock setup. According to Centerforce, the DFX assembly is rated to hold well over 1,000 lb-ft of torque while holding factory-rated tow loads.

The cool thing about Centerforce’s DFX setup is that the kit comes complete with all the stuff you need for a proper install, including a single-mass flywheel with the pilot bearing already installed, DFX pressure plate and clutch disc, ARP pressure plate bolts, throw-out bearing and alignment tool, not to mention complete instructions to take the guesswork out of doing it yourself.

Heavy Lifting
Installation of a clutch assembly on a diesel is no easy task since the transmission is extremely heavy, let alone on a 4×4 when you have to remove the transfer case to access the trans. The folks at H&H volunteered to do the R&R on Project Box Hauler. With two mechanics on the job, and a heavy-duty trans jack, they had the six-speed out in no time. Installing the new Centerforce DFX setup was fairly straightforward and is highlighted in the following photos. If you’re the do-it-yourself type, rent the trans jack; you’ll be happy you did since the days of wrestling a manual trans off your chest are over.

Road Test Results
The test-drive following the install revealed just how bad the original setup was. With the Centerforce DFX installed, the clutch was much easier to engage, with a lot less pedal pressure than the stock setup. Also, the whole driveline seemed to get much quieter and smoother, especially since we found a cracked clutch disc and loose springs in the original pressure plate. Even with the trailer attached, the engagement of the clutch is smooth and quiet with plenty of solid clamping force.

If your diesel truck is suffering from worn clutch symptoms, and it’s time to invest some time and money into the driveline, check into Centerforce’s DFX clutch assembly. It offers one-stop shopping for all the parts you need in0 a proper install. Better still, it is more capable of handing the high-torque loads of a diesel.

(928) 771-8422

H&H Diesel Performance
(928) 632-5317

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