Re: [A/S] Chevy Silverado Duramax Allison

["Oliver Filippi" <ofilippi@xxxx>]

Patricia,

I do not own one. However, I did consider buying one but didn't want to
spend that much money at the time. If I was flush I would have bought the
2500HD extended cab, short bed 4 x 4 version. Instead, I bought a 6.1 liter
gasoline version (new engine design), plain 2500 (not the HD). I did test
drive the Duramax, and was very impressed with its performance lightly
loaded. I'm sure it would perform well under heavy loads, as the amount of
torque the engine can put out (even at low RPM) is awesome. The reason you
can't get a Duramax/Allison in a Suburban or Yukon is that the frame and
floor pan do not have enough clearance for the Allison transmission.

I have several friends who have since bought the Duramax/Allison pickup.
They all love them.

One is a magician friend who hauls a trailer filled with his magic props and
illusions from show to show.

A Chevrolet service manager told me the following when this power train
first came out:
If one of these vehicles came in with an engine or transmission problem, the
dealer was instructed not to touch it, but call GM. The manufacturer would
send a factory technician to check it out. In many cases, they would
replace the engine and transmission and ship the removed unit to the
engineering department for analysis to find out what went wrong and why.

This strikes me as a manufacturer taking the performance of its product
seriously. The fact that they did not use an existing Hydramatic
transmission for the diesel, but built a new one derived from their heavy
trucks is another example. The Duramax has so much torque that it would
destroy a lesser transmission. Also, the Allison has a retarder to provide
engine/transmission braking when descending a hill and thus save your
brakes. The transmission computer can sense when this is necessary and
activate it automatically.

As you probably know, the Duramax engine was developed by Isuzu of Japan
(which GM owns) which has a lot of diesel engine expertise. The engine was
one of the first of the new breed of diesels which utilizes a computer
controlled "common rail" direct injection system. This means that the fuel
injectors are electrically actuated (not dependent on the pressure and
timing of the mechanical injector pump) so a computer can control the timing
and amount of fuel injected. This is how they get the relatively quiet idle
and minimize "diesel knock", and also get improved fuel economy. Now
Cummins (Dodge) and Navistar (International, Ford) are starting to copy this
technology.

I do own a 2002 VW Jetta with the 4 cylinder, 1.9 liter TDI (turbo direct
inject) diesel engine [the same technology as the Duramax]. It is aesel is more expensive to
maintain than a gasoline engine (assuming comparable quality engines). Quite
the opposite, just put in clean fuel, diesel engine rated oil and change it
frequently.

Diesels require a different kind of maintenance than a gasoline engine. You
must have clean fuel, properly functioning fuel filters (periodically drain
the water out of them - if you happened to get a bad batch of fuel) and
clean, turbo diesel rated, engine oil. [Diesels operate at a compression
ratio approximately twice that of a gas engine, so there tends to be more
combustion byproducts getting into the crankcase which have to be
neutralized by the additives in the oil. Also, the turbocharger is mounted
in close proximity to the exhaust manifold (very hot) and the engine oil is
pumped through the turbo bearings. This acts like a flash oil cooker. If
the oil (and the additives) can't take the heat (and break down) the engine
and turbo will not be adequately lubricated and will self destruct.
Typically the oil change interval on a diesel engine is more frequent, and
the amount of oil required is greater than that of a comparable gas engine.
This is the only greater expense item I can think of regarding a diesel vs.
a gasoline engine.

No tune ups or spark plugs or ignition wires, though you might need glow
plugs at 150,000 miles or so.

If you have never owned a diesel, there is one other caveat. Water in the
fuel can do a lot more damage (and cost a lot more to repair) to a diesel
than a gas engine. This is because of the diesel's very high pressure fuel
injection system, which depends upon the fuel to lubricate the high pressure
pump and injectors. If these parts rust it's all over - they must be
replaced, and are expensive. Gas engines, typically do not have rust prone
parts in the fuel system. This is why clean fuel is a MUST for a diesel
engine. Years ago, I used to buy diesel fuel for my Mercedes at truck stops
because they knew how to handle it and ere careful about water in the fuel
and had big filters on their pumps. Nowadays, gas stations with diesel
pumps usually have adequate filters too.

Most of the problems associated with the ill fated Oldsmobile diesel of
yesteryear were caused by water in the fuel (and an inadequate fuel filter)
rather than the popular notion of a poorly designed engine. Extended oil
change interval, then in vogue for gas engines didn't help either. [Contrary
to the folklore, the Oldsmobile diesel wasn't a converted gasoline engine;
though it did have the same overall dimensions so it could be machined on
the gasoline engine line. The only parts that were interchangeable between
the gas and diesel Oldsmobile engines (other than perhaps some screws) were
the valve covers!]

At the risk of alienating the Ford and Dodge truck fans, I think you will be
very satisfied with the Chevy Duramax/Allison pickup. Also, I think you
will find that the Chevy has a more comfortable ride (loaded or empty) than
the Ford or Dodge. If you don't need a lot of leg room in the back (aren't
driving with more than two people very often) the extended cab is shorter
than the crew cab and significantly more maneuverable. The seat folds up to
provide more cargo space.

Hunter is right, a crew cab full length bed is Looooong, and difficult to
maneuver. I can barely make a U-turn from a turn lane onto a two lane road
in the opposite direction - that's with a short bed extended cab. No way
with a long bed or crew cab or both.

If you want to go "whole hog" consider the four wheel steering option, which
adds around a thousand dollars to the price. Besides dramatically improving
the maneuverability especially in parking, (or making U-turns) it is
incredible for trailer towing - like putting steering wheels on the front of
the trailer. NO SWAY! At highway speeds, both the front and rear wheels
turn in the same direction, thus the tow vehicle effectively moves sideways
relative to the trailer, and there is almost no pivoting at the hitch ball.
This, in turn, practically eliminates fishtailing, as the trailer does not
pivot relative to the tow vehicle. [At a trade show, I spoke to a Delphi
engineer who worked on this. He said it is unbelievable how much of an
improvement the four wheel steering is for a tow vehicle pulling a trailer.]

I have rambled on here, but I hope you find my comments useful.

Good luck,

Oliver Filippi