Dirty And Proud: Joe Coffman’s “Thrill Billy” Mud Racing Chevy Truck

Photos By Dan Prince

There may be some like it, but this 2004 Chevy Colorado is Joe Coffman’s, and undeniably so, given its appearance and character. With a lot of money, time, sweat, and tears, Coffman turned the single-cab workhorse into a thoroughbred performer bound for speed through and across the mud.

Coffman first came into possession of the Colorado in 2008, having purchased it for a mere $3,000 from Copart.com, a national auction clearinghouse for salvage title vehicles. The man’s vision portended of a true racer, meant for one thing and one thing only: mud racing.

To that end, Coffman employed his friend and professional builder Jason Linden to help craft a new life for the Colorado. From the tires up, it would be nothing but the best for “Thrill Billy,” Coffman’s nickname for the truck.

How It All Began

When not out working on his racing technique, Coffman, 36, can be found in his custom shop, Coffman Custom Machine in Grain Valley, Missouri. Several projects file through the shop in any given week, so the man is never stuck in a dull moment. Even after close to 20 years of exposure to seeing, racing, and building these 1500+ horsepower monsters, Coffman has never lost touch with the thrill of the sport and its enthusiasts.

One of Coffman’s earliest memories in mud bogging dates to when he was just eight years old. His uncle, Mike Cullen, was an avid racer in Midwest and Southern events, and made quite a name for himself all through the 1970s, 1980s, and early 1990s. Before his retirement, Cullen raced in an AMC Jeep CJ-7 called Mud Tough. “[It was] stretched out full length, front and back, with a blown alcohol big block Chevrolet motor in it,” Coffman recalls.

In 1986, uncle Mike took young Joe to an event in Fredericksburg, Missouri, where Coffman was introduced to the pleasures of the motorsport. “My uncle was actually there to [sell a vehicle], and the guy wanted to race and see how it did before he bought it,” explains Coffman. “We raced it then and there, and the transmission blew up on the starting line. We tried it again the next day with a Powerglide, but that one blew up too!”

Years later, in 2004, Coffman’s formal entry into mud racing saw him behind the wheel of a 1984 Chevy three-quarter-ton truck, with a 468 cubic-inch big block V8 putting power to 40-inch tires. “That truck had me working three weeks straight, up until four in the morning sometimes, trying to get it ready for race day.” Such dedication and perseverance for the sport has followed Coffman all his life.

Coffman next to his pride and joy.

Thrill Billy Comes to Life

When it comes to his favorite subject, the Thrill Billy Colorado truck, Coffman is never at a loss for words. “I got it in late 2008 from Copart.com with the intention of building it from the ground up,” explains Coffman. He and Linden put their heads together and over the course of several months, turned the broken workhorse into a mud-slinging tour de force.

A lot of factors have to be taken into account when constructing a mud bogger. Given that its main purpose will be to charge through waterlogged soil, a truck of this nature has to be prepared the right way–lower the weight, lift the drivetrain, mount bigger wheels and tires, and push the power output to its limits.

The Colorado had been issued a salvage title for a fairly minor bit of damage in the rear, where it had a bent tailgate and bumper from backing into an obstruction. Linden bought and picked up the truck from Wichita, Kansas, and drove it back across state lines to the shop, a trip that took Coffman just eight hours to do.

The Colorado's roll cage frame.

Linden and Coffman set about fabricating a customized chassis composed of a Toyota 53-inch frame in the middle with a round tube, ladder-bar front and a rectangular tube, four-link rear, all weighing in at 2,600 pounds. A carbon fiber belly pan was mounted to prevent mud from sticking to the underside.

A shot of the Koni shock and Afco spring coilover suspension in front.

For suspension, the guys used a coilover setup with Koni adjustable shocks and heavy-duty Afco springs. The front and rear axles are 10-bolt GM (3.73:1 gear ratio) and 40-spline Strange 9-inch (4.56:1 gear ratio), respectively, which channel out one of two tire setups that the truck alternates between, depending on the track.

For softer mud, Coffman uses 36-inch Power Pro Racing Bigger Digger paddle tires; on regular mud, custom-cut Interco 44-inch STL Super Swamper tires are used. The wheels are all made by Bassett using CCM Wide 5 adapter plates, with 15×8 beadlocks on the front and 15×16 beadlocks on the rear.

At the heart of the beast is a truly breathtaking custom-made V8 from Donovan Engineering, assembled by Coffman. It’s 715 cubic inches of fury, with a 5-inch bore, GRP aluminum connecting rods, a Bryant crankshaft, 55mm COMP camshaft, CFE heads, and Braswell split Dominator carbs.

And did we mention that this monster uses four stages of nitrous? “It’s easily a two-thousand-plus horsepower machine,” says Coffman. We don’t doubt it!

Matching that badass engine is an equally badass transmission: an M&M Turboglide TH400 2-speed manual with a special NOS converter and 1:1 transfer case, controlled by a Hurst Quarter Strike shifter. Mounted in the rear is a Moroso transmission cooler. For stopping power, the Thrill Billy makes use of Wilwood discs all around, with aluminum hubs and rotors up front and lightweight rotors out back.

What It All Comes Down To

Some people want to be rock stars, others want to be social workers, and still others want to be burger flippers that get paid $15 an hour. For Coffman, however, the calling has always circled back to mud. “You know those yearbook quotes–‘Future Leaders,’ ‘Future Farmers,’ stuff like that–well, my dream was to be a mud racer,” he chuckles. “It goes pretty deep.”

Off Road Xtreme salutes you, Joe, and wishes you the best in the mud as you and Thrill Billy pursue many winning seasons to come. Check out YouTube to see some more incredible action from this mud truck, and if you’ve got a rig that’s equal parts attitude, performance, and badass, then throw us a line on our Facebook page.

About the author

David Chick

David Chick comes to us ready for adventure. With passions that span clean and fast Corvettes all the way to down and dirty off-road vehicles (just ask him about his dream Jurassic Park Explorer), David's eclectic tastes lend well to his multiple automotive writing passions.
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