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Bruiser Jeep Wrangler JK Cummins Diesel Conversions

2007 Jeep Wrangler Unlimited Offroading Downhill
Phil Howell | Photographer
Posted May 1, 2012

Finally, a Diesel Wrangler Conversion that Works and is Available Now

The Jeep world went wild with anticipation when Mopar announced a diesel conversion for TJ Wranglers, utilizing their 2.8L diesel mill. When it never materialized, people were not only let down, they were angry with Chrysler, as well as us, for announcing the still-born conversion as fact.

Diesel lovers rejoice! Diesel Bruiser Conversions is swapping Cummins diesels into not only CJ, YJ, and TJ Jeeps, but has perfected the JK Wrangler swap, as well. The Cummins mill and GM transmission interface with the JK’s CANbus system and there are no warning lights or issues. Jeff’s Jeep Yard in Florida, River Raider Off Road in Pennsylvania, and Trail Jeeps in Colorado are performing the Diesel Bruiser conversions.

Diesel Bruiser Conversions removes the 3.8L engine and 42RLE factory automatic and replaces it using the 4BT Cummins turbo diesel, utilizing Bruiser conversion brackets, a mechanical bellcrank assembly with Lokar stainless throttle and t.v. cable for the Raptor 700R4 automatic, as well as a bracket for the floorboard to accept a manual throttle pedal. An AC and alternator bracket enables the swap to re-use the existing AC compressor and alternator from the 3.8L. The serpentine belt is upgraded to an eight groove belt, along with the AC clutch and alternator pulley.

Custom AC lines go to the factory compressor in its new location. The battery tray relocates the battery and the fuse /relay box for proper clearance for the cold air intake and turbo. The wiring harness is completely re-engineered to control all engine functions as well as communicate with the factory ECM through a S.I.M. (Systems Integration and Management) computer.

The hydraulic motor mounts are designed to remove the 4BT’s vibration and are located in the custom engine mounting bracket assembly. The gear-driven power steering pump for the 4BT is utilized and high-pressure and return lines are custom made to connect to the OE power steering gearbox. The pump makes enough pressure to operate aftermarket ram assist or full hydraulic steering systems as it’s designed to operate a hydroboost brake assist system.

The factory radiator and fan assembly are retained. The 4BT does not require an extreme cooling system to maintain the proper temperature range of 180-degrees F. The lower water neck is replaced with a custom-built neck that allows you to re-use the factory lower hose from the 3.8L. The upper hose is replaced.

The braking system is controlled by a Stainless Steel Brake Corporation (SSBC) vacuum pump and reservoir canister to create vacuum for the braking system due to the diesel engine’s inherent lack of vacuum. The engine is mated to the 700R4 Raptor transmission through a Bruiser adapter and flexplate. The transmission is mated to the factory transfer case through a custom adapter and broached tailshaft assembly. The cooling lines are custom for the transmission as are all brackets to attach the factory shifter cables to the transmission and transfer case. This allows re-use of OE transmission and transfer case shifters in their factory locations. OE-length drive shafts work with up to six inches of lift.

The Diesel Bruiser JK came to our photo shoot with Teraflex Pro LCG suspension installed. Front and rear ends were stock, but by the time you read this, Jeff Garland, the founder and owner of Diesel Bruiser Conversions and Jeff’s Jeep Yard, will have built custom Dana 60 front and rear ends for his JK Unlimited.

Jeff’s diesel JK is producing 402 lb-ft of torque at 2,100 rpm (off-idle torque is 280 lb-ft!) and 140 hp at 2,700 rpm. It’s returning 28 mpg in the city and 32 on the highway. It handles as a JK should and works well off-road. With all that low-rpm torque, you seldom have to spin a tire in the dirt with the Bruiser.

Diesel Jeep fans go wild!

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