from a choice of three engines: the Duramax Diesel 6600, the Vortec
6000 and Vortec 8100.
up, the all new Duramax Diesel 6600 offers an industry leading
300 horsepower and 520 lb-ft of torque. GM partnered with Isuzu
Motors to create this diesel specifically for the HD trucks.
It has a 90-degree, direct injection, turbocharger with 4 valves
per cylinder. When combined with heavy use of aluminum in places
Duramax 6600 at home in the Silverado
like the cylinder
heads, crankcase, and intake manifold, fuel efficiency has been
raised 25-40% over gasoline engines and 15% more than the previous
generation 6.5L turbo diesel. The entire engine weighs only 836
pounds, or 379kg for a power to weight ratio of .79hp/kg. NVH (noise,
vibration, and harshness) levels, normally somewhat high in diesels,
have been reduced so much that GM claims several people have tried
to start the Duramax while it was already running.
Duramax 6600 mated to the Allison 1000 automatic transmission
will be offered with two transmission options: a six speed manual
and Allison automatic.
6-speed manual transmission will let owners control the entire power
curve of the engine. It has the potential to handle up to 26000lbs
of Gross Combination Weight - able to easily deal with the 22000lbs
maximum of the HD.
1000 automatic transmission is designed to handle Gross Vehicle
Weights of up to 19,850lbs. and Gross Combination Weights up
to 26000lbs - much more than the 3/4 or 1-ton trucks will ever
weigh. The Allison 1000 is also designed to handle 545 lbs-ft
of torque and 375 gross horsepower. A driver will be able to
choose from two modes of drive: Normal Mode for day to day driving
and Tow/Haul mode for when the truck is pulling a load. Fuzzy
logic is incorporated into the transmission's software to actually
'learn' and adapt to the driving habits of the owner. Sophisticated
algorithms also estimate when the transmission
HD Chassis with Duramax 6600 Diesel
downshifted without the driver every having to shift - though this
feature can be manually disabled. Transmission fluid does not have
to be changed for two years or 50,000 miles.
for the Allison are as follows: 1st
- 3.10, 2nd - 1.81, 3rd - 1.41, 4th - 1.00, 5th - 0.71, Rev - 4.64.
GM spent twice
as long testing the Duramax than any other previous engine at a
total time of 2500 hours - roughly equal to 200,000 miles of wear
and tear and at a severity level GM calls the 98th percentile. Though
developed in Japan, the Duramax will be produced domestically in
x Stroke (inches)
The Dodge Cummins Diesel described above is an Inline-6 contrary
to the V8 description PUTC originally published from the GM Press
Release obtained during the introduction of the new HDs. PUTC regrets
any confusion this may have caused.
While GM appears
to be leading the class for now in the diesel engine wars, don't
expect to see Ford and Dodge sit idly by. For 2001 Dodge is expected
to offer the ETH Cummins with 245HP and 505ft-lbs of torque when
equipped with a 6-speed manual transmission. Ford is still secretive
about their response.
The base V8
engine used in the Heavy Dutys is the Vortec 6000. This is the same
engine used in the light duty trucks but tweaked to add more horsepower
and torque (325hp@5000rpm and 370lb-ft@4000rpm). A 5 speed manual
is standard with this engine choice and the venerable 4L80-E automatic
is an option.
The all new
Vortec 8100 also sets a few benchmarks for the HDs. With 340hp@4200rpm
and 455ft-lb@3200rpm owners can choose the same 6 speed manual or
Allison transmissions available on the Duramax Diesel. Again, like
the Duramax, the Vortec 8100 claims to be a class leader in horsepower
A few notes
about towing on the trucks. In the 1999 models, trailer ratings
equaled the GCWR - vehicle weight where vehicle weight is EPA curb
weight plus the driver and one passenger and the rating is rounded
down to the nearest 500 pounds. In the 2000 models, trailer ratings
equal the GCWR - vehicle weight where vehicle weight is base curb
weight plus the driver and the rating is rounded down to the nearest
100 pounds. The new rating methodology more accurately reflects
the full extent of the towing capabilities. With the factory installed
weight distributing hitch the trailer weight rating can reach up
to 12000 lbs. And with a fifth wheel hitch that capacity grows to
nearly 16000 lbs. Both the Silverado and Sierra have GCW ratings
of 22000 lbs. GVW is 9200 lbs for the 2500HD and 12000 lbs for the
up front comes from IFS and a torsion bar to provide better
fuel economy and improved GVW ratings. Brakes are now four
wheel drive discs with larger rotors and brake pads to improve
wear. GM claims 30,000 - 40,000 miles of brake life under
normal use conditions for the HDs.
hopes to compare the new GM Heavy Dutys to similarly equipped
Dodge and Ford models in the near future. Unfortunately we
did not get to have time behind the wheel at this introduction.
were no pricing announcements on the trucks shown, so we have
yet to see how affordable the trucks will be when they go
on sale in early 2000.
Suspension - note the torsion bar for increased towing capabilities.