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 Since the previous owner had...  Since the previous owner had upgraded the donor Dodge with a 4-inch exhaust, it made sense to adapt it to the GMC. The two systems were nearly identical in length and only required McCully to rework the downpipe and hangers in order to make it work. |  Remember those 3 inches of...  Remember those 3 inches of extra bellhousing length? Coupled with the fact that the Cummins needed to sit lower in the engine compartment (just to clear the hood!) meant a custom transmission crossmember would have to be built. A few sections of 2x3-inch 1/4-wall steel tubing were used to support the drivetrain yet still clear the front driveshaft and leave room for the 4-inch exhaust. |  The new transmission location...  The new transmission location meant the hole in the floor would have to be opened up to accommodate the new shifter position. After rowing through the gears a few times, McCully found the shift lever would hit the center console. He pulled the shifter mechanism out of the NV4500 and heated it up with a torch in order to bend it for clearance. A new carpet kit for an automatic transmission truck (no hole) will have to be ordered to make the new install look factory. |
With everything physically bolted in place, McCully enlisted the help of Jesse Slye and Adam McLauflin to plumb and wire his new mill. The GMC's fuel feed and return lines were hooked up to the Cummins lift pump on the driver side of the engine. The GMC's electric lift pump was then replaced with a short piece of 3/8-inch metal line. McCully was able to reuse the Dodge's mechanical throttle cable by retrofitting an accelerator pedal from a '96 gasoline GMC truck (the 6.5L engine is drive-by-wire) and reworking the end of the pedal linkage to achieve wide-open throttle. At this point, the power steering pump was upgraded with a unit from PSC to supply the GMC's hydroboost brakes yet still mesh with the drive gear on the back of the Cummins vacuum pump.
 Wiring proved to be the slowest...  Wiring proved to be the slowest part of the swap. McCully purchased factory-wiring diagrams from his local Dodge and GMC dealerships in order to make everything work again. Don't even bother trying to get this part right with a Chilton's or Haynes manual! Basically, the factory Dodge/Cummins computer and its wiring harness remained intact and got transferred directly to the GMC. From there, the Cummins fuel cut-off relay was supplied with keyed ignition power, and the computer was grounded and fed a constant 12 volts to supply its memory. It's every bit as involved as it looks, which is why the factory wiring diagrams are so critical. |  With the engine wired, all...  With the engine wired, all that was left was to shorten the Dodge radiator hoses (the radiator is now closer to the engine), hook up the intercooler plumbing, and fill the system with coolant. |  For a personal touch, McCully...  For a personal touch, McCully added a conical air filter and had Bryon Cipriani of Designit Prototype machine this one-of-none aluminum GMC Cummins valve cover. As we went to press, McCully has been driving his Cummins-powered GMC for a few weeks. He still needs to build an aluminum fan shroud for the radiator, get the stock GMC speedometer, tachometer, and cruise control working, and have A/C lines made to connect the Dodge compressor to the GM system. McCully is also working with Atlas Spring to develop a stronger set of front leaf springs to support the weight of the new engine. |