Q. I have a question regarding my 2004 Dodge Heavy Duty 5.9 high-output diesel. I would like to increase the pulling power. Do you have any suggestions on how to do that and still be street legal?
— R.K., Nevada City, California
A. Do you mean that you want to be able to pull more weight than the truck is rated for, or that you want to increase horsepower and torque? Either one can void your warranty if damage occurs as a result. We don’t recommend towing more than the truck is rated for. Many diesel owners modify their trucks for more power, but while California doesn’t currently perform periodic smog checks on diesels, you could be subject to a spot check for smoke opacity. Engines that have their fuel delivery increased may not pass these tests (not “street-legal,” per your requirement).
Ken Freund’s more than three decades of auto-repair experience and 20-plus years of RVing helped him author numerous books and articles on vehicle repair. In addition to RV Clinic and Performance, he writes the Powertrain column in MotorHome magazine. Ken has been a California Automotive VO-Tech and Smog-Test Program Instructor and an ASE-certified Master Automobile Technician.