Meet our new 6.7L Cummins-powered test mule. It's an '09 Dodge Ram 2500 Mega Cab with a little more than 10,000 miles on the odometer. The truck was loaned to us so we could test a number of performance products on the new Ram and see how well the 6.7L would respond.
Of course, by the time we got ahold of the truck, the owner had already made a few modifications. The diesel particulate filter had been replaced with a 5-inch turbo-back exhaust and the EGR system was blocked off.
The owner had also added an S&B air intake, AirDog fuel system, and 80hp injector nozzles from Dynomite Diesel. In this configuration, the truck made 360 hp and 944 lb-ft at the wheels. Not a bad start-but we wanted more.
We have a big horsepower goal in mind for this Mega Cab, so our first step was to get in touch with North American Diesel Performance. We were interested in NADP's Heavy Hauler 68RFE six-speed automatic transmission. NADP is one of the few transmission builders putting together bulletproof 68RFEs, and it sent us a unit it said would handle anything we throw at it.
After the transmission was installed at Flynn's Shop in Alexander, Illinois, we followed NADP's standard break-in procedure, which allowed the transmission control module to learn its new shift points and adjust accordingly. Once the transmission was broken in, the shifts were quick but silky smooth at the same time.
With the NADP transmission in place, it was time to head back to the garage and add a modified CP3 injection pump from Industrial Injection, ARP head studs, and a mild performance tune from H&S Performance. Here's how our first installment of Project 6.7 panned out.
North American Diesel Performance is one of the few companies putting together bulletproof
This adapter harness from NADP is the key ingredient in making its Heavy Hauler 68RFE shif
With the truck up on a lift, Chad Flynn, of Flynn's shop, removed all bracketry, disconnec
Next, the transmission cooler lines and dipstick were removed, the transmission control mo
Although it may be hard to see here, a 33-inch extension with a 14mm socket was used to re
Then the transmission was lowered, all sensors were swapped over to the NADP Heavy Hauler
After that, the Sun Coast torque converter was filled with synthetic automatic transmissio
Next on our to-do list was ditching the factory CP3 injection pump in favor of a modified
...followed by the fuel line running to the high-pressure fuel rail.
Then we removed the serpentine belt (the tensioner is on the bottom of the engine), the pl
Before we installed the modified CP3, a light coat of engine oil was applied to the shaft'
To make sure our fuel rail was getting as much fuel as possible, we installed a fuel press
Switching gears once again, we moved to the topside of the engine to install a set of 12mm
The factory head bolts are 12 mm in diameter and have 18mm heads (above), but when this 6.
Here's a look at the ARP head stud, washer, and 12-point nut installed (arrow). It should
Each head stud was torqued to the following specs recommended by ARP: 77 ft-lb on the firs
We encountered one minor problem after all the head studs were installed. The rocker box w
Adaptive Learning With The TCM
With the new transmission in place, the crossmember and brackets were reinstalled, and the truck was topped off with 15 quarts of ATF and taken for a testdrive. Because the 68RFE is electronically controlled, an adaptive learning process was performed following the install. This was done in order for the TCM to recognize and adapt to its new shift parameters. We simply took the truck on a 20-mile drive, making frequent stops to allow the transmission to run through all of its gears. Then the fluid level was checked, topped off, and re-inspected after another testdrive. We followed NADP's break-in procedure precisely and only used light to moderate acceleration until the transmission had accumulated 300 miles of city driving. Throughout the break-in procedure, the transmission progressively softened its harsh shifts and began operating as smooth as it had when it was stock, albeit with quicker gear changes.
Baseline Dyno Numbers
We paid Scheid Diesel a visit to baseline the 6.7L, and it made an impressive 360 hp and 944 lb-ft of torque with the modifications listed above. The factory turbo pushed 28 psi and the EGT never exceeded 1,350 degrees throughout the run. Stock 6.7L trucks typically put down 260 to 280 hp at the wheels, so we'd say Dynomite Diesel's 80hp injector nozzles definitely performed as advertised, especially since they were supplied with plenty of fuel thanks to the 100-gph AirDog fuel system. And no doubt, the Heavy Hauler transmission was getting the power to the wheels. Not a bad start, considering we hadn't brought aftermarket tuning into the equation.
Project 6.7 Stage One Dyno Test
After the new CP3 and ARP head studs were installed, we headed back to Scheid Diesel for another run on the dyno. We uploaded a mild tune from H&S Performance and the truck made 420 hp and 1,183 lb-ft. Throughout this dyno run, one thing was for sure-we had plenty of fuel on tap. The factory turbo pushed 35 psi but struggled to keep up with the fueling, which resulted in excessive smoke and a peak EGT of more than 1,600 degrees. Not to worry, we're looking into installing a set of twin turbos next.
925 Tower Ave.
Dynomite Diesel Performance
13675 Roosevelt Rd SE
1863 Eastman Avenue
4960 North 13th St
1201 South 700 West
Salt Lake City
2217 Old Dennis Rd
1412 Creek Trail Dr
4012 S. River Road