GM Adds Enhanced Duramax To G Vans
New to Savana/Express, the diesel V-8 proves quiet and smooth, but owners will have to judge its efficiencies.
Tom Berg
Senior Equipment Editor
General Motors has brought back diesel power to its G series cargo vans, which for several years have been gasoline-only, while Ford has been selling big numbers of diesel vans and van-chassis to commercial users.
Installation of GM’s improved 6.6-liter Duramax 6600 V-8 into the 2006 Chevrolet Express and GMC Savana results in a quiet and smooth-driving vehicle that should turn in good fuel economy in these days of high fuel prices.
GM has been doing fine with gasoline-only power in its vans, which were redesigned for the 2003 model year and have some access features that Ford’s E series does not. Ford is now GM’s only competitor in this segment since Dodge dropped its B van in favor of the Eurospec Sprinter. The diesel gives Chevy and GMC customers another choice and dealers something else to sell, executives said.
The van version of the turbocharged and aftercooled Duramax makes a conservative 250 hp and 460 lbs.-ft. of torque – about 24% less than in pickup trucks – because that’s all van users demand, GM executives said during a recent demonstration of cars and trucks in Salt Lake City. Put another way, the Duramax’s power matches the output of Ford’s non-aftercooled Power Stroke turbodiesel in its E series vans, which has proven sufficient for customers who buy vans for work, not personal use.
The Duramax 6600 features a host of improvements for ’06. They include enhanced electronics in the control module for more precise operation; a variable-geometry turbocharger with recurved and more efficient blades; higher-pressure fuel injection, with injectors reoriented to spray directly onto fast-heating glow plugs for better cold starts; better cooling of exhaust gas in the EGR system; a stronger water pump; and a revised air intake system with a resonator to cut noise. Two-piece rocker covers allow mechanics to easily get at injectors and other parts in the cylinder heads.
The ’06 Duramax runs so cool that GM offers a fuel-fired coolant heater. Executives expect this to be popular in cold climes where quickly-heated water can better supply Btu’s to the cab heater and to auxiliary heaters in the cargo compartment. The coolant heater automatically switches on at cold start up, and off when temperature approaches operating levels.
Drivers of Chevy and GMC vans will certainly notice the new diesel, and those in northern states might appreciate its clean, no-sweat cold starts in winter. But if they’ve not driven late-model Duramaxes in pickups, they’ll probably be unaware of the ’06 model’s advances. And of course they have other things on their minds, like making the next delivery, how to handle the next service call or wondering when traffic congestion might ease up.
When I drove this GMC Savana 3500, I had no delivery or job pressures. Temps in Salt Lake City were pleasant, mid-day traffic was light and the van was empty. So all I could observe was the diesel’s quietness and smooth operation.
For certain, the DuraMax in the Savana was quieter than a 6-liter PowerStroke in a Ford Econoline van, which our GM hosts had obtained for comparisons. That was true while we stood outside listening to them idling and revving a bit. But the Ford, which I also drove, was nicely hushed inside and actually seemed a little quieter than the GMC while moving down streets and freeways. If the vans had carried loads or pulled heavy trailers there may have been more discernable differences, but there weren’t while running empty.
The Ford would seem to have an operating edge with its five-speed TorqShift automatic transmission compared to the four-speed Hydra-matic in the GMC. But the Ford’s extra ratio was simply not perceptible under light load. It should theoretically keep the PowerStroke at a more efficient speed, but whether this converts to better performance and fuel economy is an open question. GM engineers say their Duramax now delivers better economy than the International-built PowerStroke, and owners might see that if they keep careful fuel-consumption records.
The Hydra-matic is a 4L85-E, a stronger version of the 4L80-E used in most of GM’s three-quarter-ton gas-powered pickups. Certain internal parts of the 4L85-E are beefed up to take the diesel’s higher torque, engineers explained, and the transmission is strong enough with the van-rated Duramax that they don’t have to use the costlier and bulkier Allison 1000 that goes in more powerful Duramax-and gasoline Vortec 8100-equipped pickups. The Hydra-matic shifted very smoothly and was a pleasure to drive.
The G van’s front suspension and crossmember have been strengthened to take the diesel’s slightly higher weight. But necessary changes were minimal, engineers said, and they certainly didn’t harm the van’s ride quality. It and other measures of noise, vibration and harshness that designers strive to mitigate were entirely in keeping with the high comfort levels we’ve come to expect from modern trucks. One thing unavoidable in this truck configuration is the doghouse, which limits the driver’s and passenger’s lateral leg room, but designers worked hard to reduce the protrusion and one gets used to it anyway.
GM will offer the Duramax-powered G cargo vans with integrated panel bodies and in cutaway cab-chassis versions. Executives figure that 10% of all van production will get the Duramax. One might think that it would be higher, but any diesel carries a hefty price premium – typically $5,500 in a light-duty truck – that takes a long time to pay for in fuel savings. And current gasoline engines are efficient and long-lasting, GM executives contend.
However, if diesel sales prove stronger than forecasted, they won’t be unhappy, either.
