So just what's involved in removing a diesel particulate filter for servicing?

      Combined catalyst-DPF devices, which one truck builder calls "cans," look like big mufflers, but weigh more – 80 pounds or so. That includes 50 to 60 pounds for the DPF element, which is a honeycomb made of ceramic that is coated with precious metals.
      Cans will usually be mounted under cabs or in vertical stacks. A "compact" version to be used by Mack and Volvo resembles a large coffee maker; it will mount under the cab at the passenger door, accessible without crawling under the truck. Cans or stacks might need special lifting devices, and those in other under-cab locations might require a creeper and a transmission jack to get to and handle.
      Dodge, Ford and General Motors all say they will split the oxygen catalyst and DPF in their light trucks and some mediums. The catalyst will be close to the engine and the DPF will mount a few feet farther downstream in the exhaust system. Both are smaller and lighter in weight than the cans on heavy and some medium trucks.
      Although those two parts will muffle most noise, the builders will also use a resonator to take out whatever "rapping" might be left. These systems will be hung on vehicle frames and easy to get at, though they could block access to transmissions where power take-offs are used.
      Midrange tractors, like those used in P&D operations, will probably get vertical stacks with the aftertreatment device also mounted vertically. The device will be heavier than a current muffler, so the mounts will be heftier. Devices will also be more bulky and take up a few more inches behind cabs, which should be OK on most tractors, but could be a problem for bodies that are now mounted close to the cab.
      Midrange trucks are more complicated. Because they are fitted with a wide variety of bodies and equipment, manufacturers will have to use a split system, as on light trucks (except for Cat engines, which will use only a DPF). But more often they'll be a single-unit can, like those on heavies. Usually the can will go beneath the cab, off to the right. In some cases it will be under the steps on the curb side. The tailpipe will run rearward on the frame or up a rear corner on the cab.
      The longer the chassis and wheelbase, the easier it will be to accommodate the aftertreatment parts. However, some bodies are low – beverage and utility bodies come to mind – and take up all the frame space behind the cab. Here the exhaust system must be as compact as possible. Short-wheelbase chassis – or ones fitted with pusher axles like those on heavy dump trucks – also leave little room for the new exhaust systems. That's why the EPA gave them special consideration in its minimum mileage requirement.

Maintenance continued...