GOS Performance's Ford Bronco Cummins Conversion

Can you stuff a straight-six into a half-ton chassis?

Published in the August 2010 Issue August 2010 Build, Cummins, Feature, Installs

BeforeSome swap projects are a little cliche. But getting a 12-valve Cummins to fit into a 1996 Ford Bronco? Now we have something unique.

Jerry Schmidt opened GOS Racing and Performance in 1994. Jerry says "It grew to a point where I was ready to step aside. Aden McDonnell and his family were customers of ours and heard I was going to sell. Because they were such good customers and friends, I made them an offer they couldn't refuse."

Aden came to Washington before he took over GOS, and saw Jerry's new 2005 F350 Harley Davidson truck. Jerry says "he liked my truck so much that he bought one when he got back to Montana. Months later he was complaining about how much work it was to keep the Harley truck clean and was thinking about getting rid of it. I suggested he look for a 99.5 Ford with a 7.3 and put a Cummins in it, the rest is history. He hated me for a while when he did the first conversion, but still has the 99.5 F250 with a Common Rail.

That set the stage for GOS Performance to become one of the premier Cummins swap shops in the industry. Having done close to 20 conversions, Jerry suggested something different to Aden. His idea was to put a Cummins in a full-size Ford Bronco. Aden liked the idea, and they both thought it would be a fun challenge.

The two established some guidelines for the unique project. "First, it had to be a P-pump 12-valve," said Jerry. "It needed an automatic transmission. We wanted it to make at least 500 rear-wheel horsepower. And we had to complete the conversion in less than three weeks."

That's just what the power train had to do. The Bronco also had some strict guidelines. It had to be a 1996 model year, which was the last production year of the full-size Bronco. The pair wanted it to be straight and clean without any need for body repair, paint work or upholstery. They also wanted to find a Bronco with less than 100,000 miles on it.

Jerry says it took nearly two years to find the right Bronco that fit that bill. He found one in Boise, Idaho. Jerry called a friend in Caldwell who manages the Les Schwab tire store and had him inspect the Bronco. It met the criteria, so his friend picked up the Bronco and took it back to the tire store where they installed a 4-inch Tuff Country lift kit along with new 16-inch Weld wheels and 32-inch tires.

When the Bronco arrived in Washington, Aden and Jerry started planning the conversion and assembling parts and pieces. They used Quad mounts for the motor. Those plus the A/C mounts and alternator mounts came from Auto World in Kalispell, Montana.

The engine adapter came from De-Stroked. The transmission is an E4OD from a 1996 F350 Power Stroke. Jerry says they went this route since it has a bigger bell housing so they could use a larger converter.

The transfer case is an electric-shift 1325 BW. They shortened the rear drive shaft and lengthened the front drive shaft because the transmission was moved back about two inches. New u-joints were installed on both shafts before being installed.

Automatic Transmission Specialists in Livingston Montana built the trans using a Sun Coast Extreme kit, a 4-pinion planetary and a Transgo Tugger kit. The converter is from Idaho Transmission; it's a billet triple-clutch, low-stall converter.

The P7100 has been flow matched and balanced at 490cc. Internals on the pump include a number 6 plate that is custom ground. It also has 4,500-rpm governor springs and 191 laser-cut delivery valves.

The injectors are Dynomite Diesel Performance's 80 hp sticks and the timing is set at 17.5 degrees.

The donor motor only had 82,000 miles on it, so all Jerry and Aden did was a complete reseal job from top to bottom and front to rear. The transfer case was rebuilt. The front end was completely rebuilt including the brakes. The rear end had an Eaton TruTrac differential installed.

Under the hood, Jerry and Aden used an ATS three-piece manifold which was mounted upside-down to allow for more clearance. The manifold was machined to allow the turbo to be clocked for better angles on the intercooler tubes.

Because the No. 6 valve cover sits so close to the firewall/cowl you can't get the cover off for valve adjustment. The typical solution would be to notch the firewall. Jerry thought this was a bit crude, so he came up with the idea of machining off the top off the valve cover and using dowel pins to keep it aligned when installing.

The turbo Jerry and Aden used is an Industrial Injection Phat Shaft 52/80 and will pull 48 psi of boost. The head is held on with ATS head studs.

They also used the stock Dodge power steering and vacuum pumps with custom hoses. The wiring is the Bronco's stock stripped-down harness. This way, if there is ever the need to pull the motor, there is one basic connection linking the motor to the chassis just like the 5.8L that GOS removed.

The motor came with a Banks Twin Ram which they used. The transmission is controlled by a Powertrain Control Solutions computer. With that computer, they can set any shift sequence they want, including converter lock up. It even has a `Dyno Mode' and they can data log using a laptop linked to the PCS. This data logging has let Aden and Jerry record 0 to 60 times in the 4.7- to 4.8-second range.

The exhaust and intercooler tubes were hand-built. The exhaust is 4-inch 409 stainless steel and uses a 34-inch Magnaflow muffler. The intercooler is from a 2004.5 Dodge Cummins.

Jerry and Aden also robbed the dash out of a 1996 Ford Power Stroke for the diesel tachometer and diesel-only fuel gauge.

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