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Towing
expert Andy Thomson offers his insights in every issue
of RV Lifestyle.
 Our
tow vehicle is a 1998 GMC pickup with two-wheel drive,
a 5.7L engine and 3:73 gears. We pull a fifth wheel,
23-foot Citation which weighs 6,000 pounds loaded.
On flat roads we roll along in overdrive at 2,000
rpm at 100km/hr with minor drag, but when the terrain
starts to roll or in the mountains, that's when the
truck really works. I try to stay below 3,000 rpm
in these conditions. Can we improve hill climbing
by changing to 4:10 gears? If so, could you please
explain how this would be achieved? Mechanics do not
seem to agree on this - some say the motor will rev
higher and gas consumption will increase dramatically,
suggesting that the improvement may not be worth the
expense. We like our truck, but even after modifying
the exhaust system and the air intake, we're still
not comfortable in the hills. Could you please provide
your recommendations in simplest terms?
In your columns we've read with great interest how
effortlessly Airstream trailers can be pulled. We
are entertaining the thought of sheathing the underbelly
of our Citation with light gauge materials in efforts
to reduce wind drag. I understand Airstream encloses
their framework. Any advice on this attempt? Again,
thanks for your valued information in every magazine.
Vic & Marlene Lamothe
Calgary AB
Hi Vic & Marlene:
Actual performance and the perception of the performance
you have can be two different things. A combination
that one person feels is just great may feel underpowered
to another. I once heard someone say you can never
be too rich or too thin; I would say that for some,
you can never have too much power either. Often though
people do not really mind the level of performance
their combination has but as in your case they wonder
if it is working too hard.
The 5.7L in your truck has is an engine we have towed
with for the last 30 years, most of them with the
same 3.73 gears and the 235/75 x 15 tires you have.
Until 1986 the 5.7 was only rated at 170 horsepower
and 270 foot-pounds of torque, yet they were used
extensively for towing trailers much larger than yours.
For more power you could go to a 3/4 ton truck with
a 454, but it was only 230 horsepower and it went
through a lot of fuel, oil & exhaust manifolds. Further,
the stiff suspension soon filled the much looser body
structure of those days with all sorts of rattles.
In 1987 GM added fuel injection to the 5.7, the horsepower
increased to 210 and the torque to 300, so it was
a noticeable boost. I remember the first time I drove
one of the fuel injected 5.7's and thinking how much
power it had and how well it performed. Today, I get
in one of those trucks and it feels decidedly average!
How soon we get spoiled!
The next big change for the 5.7L came in 1996, when
the Vortec series was introduced with 255 horsepower
and 325 foot-pounds of torque. When these were first
introduced, I happened to have a pre-Vortec, fuel
injected 454 Suburban here and a Vortec 5.7 at the
same time. They both had 3.73 gears and the same size
tires. We put a 34-foot Airstream on both of them
and had a little drag race...
...
(Read Andy's full article in the magazine.)
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