2004 Dodge Cummins HO Budget Hop Up
by Gary Scott
I got my first diesel in
the fall of 2003. I was nearing retirement age and my wife and I
decided that a pickup and travel trailer would be he best combination
for us as I wanted to keep the pickup bed open to haul my dirt bikes and
We were really looking
for a low mileage used diesel because I’m a Scotsman and try to save
where I can. You’ll see examples of my frugality as you read on.
I talked to many pickup
owners before buying a diesel and the 3/4 ton gas rigs were getting
around 15 mpg highway and the diesels around 20 on average. The diesel
guys were also absolutely ecstatic about the torque that made towing
effortless, so it looked like a diesel was the way to go if I was
willing to make a long term commitment.
I hadn’t heard anything
bad about any of the new quieter diesel motors at the time, so I was
initially just looking for the best deal, not a particular brand
although there were some things I liked about some models over others.
My wife and I decided
that we wanted a short bed extended cab 4X4. The reason for the short
bed was for turning radius and parking in normal sized spots, and we
wanted an extended cab so we could occasionally haul passengers. We
didn’t want a crew cab because we’d end up with a longer wheelbase and
we didn’t haul passengers that often. We didn’t think we would use the
4 wheel drive much, but since we live in northwest Oregon and expected
to keep the truck till we got to old to travel, we thought it would be a
We liked the Dodge
passenger arrangement the best because it had normal opening rear doors
and a little more back seat room than the competition. The Chevy/GMC
was a close second, but we didn’t like the suicide doors as well and the
fact that you had to open the front doors first. Ford was last because
of its small rear passenger area.
There were two things we
didn’t like about the Dodge however. It was the tallest truck and the
hardest to get into, and it had an old tech 4 speed automatic
transmission with questionable reliability, so we would have to go with
a manual if we got a Dodge. Both my wife and I have plenty of
experience with manual transmissions, so we could make that sacrifice if
we had to.
The combination of the
lowest step-in height and 5 speed Allison Automatic made the Chevy/GMC
our first choice even with the silly suicide back doors.
On Thanksgiving day 2003
a local Dodge dealer advertised a 3/4 ton short bed 4X4 with a Cummins
and six speed for about the same price we’d budgeted for a year or two
old unit. We were waiting at the door when they opened the following
The first salesman tried
to show us some different units, but when we were adamant about seeing
the advertised vehicle he passed us off to a rookie as there apparently
wasn’t going to be much profit or commission involved.
We drove the truck and
liked it with the only exception being that darn step in height.
Shortly after we
purchased the truck we went shopping for a travel trailer as we knew we
could get the best price in the off season. Within a few weeks we found
a 27 foot Jayco owned by a private party. Just as we were hooking up
the trailer it started to snow. If we hadn’t had four wheel drive we
couldn’t have gotten the trailer home as I hadn’t purchased chains yet
for the truck.
Oregon winters often
have periods of mild weather, so we had the opportunity to try out both
the trailer and the truck right away.
The truck towed the
trailer effortlessly and on mostly level ground would get 12 to 14 mpg.
We enjoyed the trailer except the hassle of hooking up and unhooking the
weight distribution hitch. I’d done WD hookups a few times before on a
car hauler trailer, but in that case it was usually just once a trip.
My wife and I like to
explore, so we were moving almost daily and I thought there must be a
better way. Being a design engineer I started working on what would
become the Fastway hitch – but that’s another story.
During the development
of the hitch I drove the truck without the trailer many times from
Portland to a metal fabrication shop owned by friends of mine in Idaho.
At higher speeds and over a couple of mountain passes I was getting 17
to 18 mpg. Not bad, but not the 20 mpg I was expecting.
The truck was geared
perfect for towing, but a little low for high speed running. With 3.73
gears, 265-70-17 tires, and the six speed manual I was turning 2200 rpm
at 72-73 mph. It would get much better mileage if it were cruising
nearer the 1500 rpm torque peak, but adding an overdrive unit would cost
more than I could recover in fuel savings.
All engines are more
efficient if they can inhale and exhale easier, but turbo diesels move
so much air that they benefit the most so I decided to see if I could
get more mpg that route.
I looked at the
multitude of intake and exhaust available in the aftermarket and once
again it looked like the investment wouldn’t result in a reasonable
payback. I especially didn’t like the noise of the straight through
mufflers offered, so I decided to see if I could do something on my own.
I pulled the muffler,
cut open the side and discovered that there were three tubes inside.
The exhaust first ran down the lower tube, had to turn 180 degrees and
run backwards through the center tube, then another 180 before running
down the top tube and out the exhaust.
That obviously wasn’t a
free flowing design, so I cut an opening in the muffler right at the end
of the lower tube and ran a piece of tubing at an angle from the bottom
of the muffler up to the exhaust pipe. I put in a flap valve so I could
adjust the flow and noise level as needed.
It turned out that I
never had to use the flap valve as apparently the rest of the muffler
now works as a resonance chamber and the noise level is barely more than
I next turned my
attention to the intake where the designers had routed the air around
the side of the air cleaner box through a small opening between it and
the fender. I knew it was restricted as it “honked” when full throttle
The air box was ABS
plastic, so I just took a short section of large diameter ABS tube and
after cutting a matching hole right in the front of the airbox, glued it
in place with common ABS cement. I covered the end of the tube with
screen to keep the large chunks out and for about five bucks had a
direct ram air intake, but it cost me another $40 for a gauze air filter
to take advantage of the increased airflow.
The combination of
intake and exhaust modifications yielded about one more mpg. Not bad,
but being a Scotsman, I was hoping for more.
I consulted my friend
and truck expert Kent Sundling – better known as MrTruck, and he
recommended an Edge module to take advantage of my breathing
I got an Edge module
that had four stages and settled on stage 2. Stage 4 yielded the most
power and a little more mileage, but the engine didn’t seem really happy
at this setting. Stage 2 gave me the best mileage and still yielded an
increase in power that you could feel in the seat of your pants.
And finally the bottom
line – on the bottom line of course. Combined with my intake and
exhaust mods I’m getting from 2 to 4 mpg more and I’m very happy with
both the truck and the results of the changes. Your results may vary of