Tow-testing Chevrolet’s New 6-Speed Silverado
We’ve complained about Chevrolet’s lack of a five- or six-speed transmission in its light-duty pickups. It’s been a competitive disadvantage against trucks from Detroit as well as those from overseas parent companies for more than five years.
Where we grew impatient is that GM had a great six-speed transmission in its light duty trucks and full-size SUVs; but it was limited to the company’s upscale GMC Denali and Cadillac Escalade nameplates.
While it was slow to migrate to the Silverado production line, when made available for 2009 we put one to the test to see if its impressive, on-paper, 9,500-pound towing capacity was well matched to the performance of the chassis and driveline.
Another Thousand Pounds
Because of the increased capability from the HydraMatic 6L80 six-speed auto transmission, the Silverado 1500 Crew Cab gained more than 1,000 pounds of towing capacity when turned by the 5.3 Vortec flex-fuel-capable engine.
To get to the high tow rating, our test model had a heavy duty cooling system. We also tried the $200 optional integrated trailer brake control that eliminates the need for an aftermarket, under-dash mounted unit. The controller is linked to the truck’s ABS system and automatically distributes correct braking force to trailers equipped with electric brakes. Like the systems from other manufacturers, it’s slick and worth every penny.
Even though the axle is a 3.42 ratio, the transmission provides a wide, 6.04:1 gear ratio that includes two overdrive gears. There isn’t a 1:1 ratio in the specs; the closest is fourth with a 1.15:1. Fifth gear is a 0.85 overdrive and sixth is a 0.66 ratio.
Because of its tow rating, we gave the truck a serious workout and pulled a load estimated at 7,500 pounds. The low, grunting, 4.04 ratio first gear was able to get the heavy trailer moving easily. Compared to normal driving without towing, shifting up through the gears was slower than when empty, but precise and solid.
With ambient air temperatures hovering right at the freezing point, transmission operating temperature from the driver information center indicated 115 degrees F. While towing heavy, the temp increased to 155 degrees when ascending grades or in higher traffic areas, but held at 147 degrees on the open road. It would be a better test in warm weather, but the truck was nowhere near 215 degrees, a common benchmark of “normal” transmission operating temp.
We liked the user-control feature of the 6L80 transmission. A column-shifter-mounted toggle switch allows the driver to manually select gear position. It’s especially useful for manual downshifting to get the engine to peak power before losing power ascending a grade, or to increase the engine braking effect when loaded or towing on downhills.
Even in the full-auto mode and the tow/haul mode engaged, the engine braking was impressive. The driveline senses acceleration without throttle and holds gears without upshifting to maintain better control.
We expected the load to push and buck the truck. But thanks to a well-balanced load and a stout tow vehicle, handling and stability during cornering was excellent despite riding on P-rated tires. The truck was confident towing the 7,500-pound load at speeds greater than 60 mph.
Aside from the improved towing performance and capability thanks to the new transmission, the Silverado’s refinement improved, too, with a quieter cab and improved mileage at highway speed.
When we weren’t towing, it seemed the wider ratio of the new transmission allowed the engine to make better use of its cylinder deactivation mode. The subtle V4 pulse was felt more frequently and for longer durations than previous drives in half-ton Silverado trucks both in town and during highway drives.
Another big improvement is roll-on acceleration for passing or other needs for rapid acceleration. The transmission’s ability to select six different gears gets the engine to its 320 hp peak in a hurry.
At 70 mph, the truck’s tach indicated about 1750 rpm and we heard only wind and tire noise — nothing from the driveline. The reduced engine workout at highway speed should equate to the engine requiring less fuel, but any gain should be marginal.
Thankfully, Chevrolet decided that truck buyers waited long enough for a transmission better suited to towing. The additional towing capacity and improved refinement are welcome additions.
2009 Chevrolet Silverado 1500 Crew Cab LT1
Base Price: $32,965
Price as tested: $37,750
Vortec 5.3L V8 w/Active Fuel Management and Flex Fuel Capability
Net Torque: 338 lb-ft @ 4400 rpm
Net Power: 315 hp @ 5200 rpm
Fuel Delivery System: EFI
Fuel Capacity: 26 gallons
Fuel Requirement: Regular Unleaded, ethanol blends to E85
Transmission: Hydra-Matic 6L60, 6-speed automatic
Rear Axle Gears: 3.42:1
Body/Frame: Body on frame
GVWR: 7,000 pounds
Front: Independent, coil-over shock
Rear: Solid axle with semi-elliptic, variable-rate two-stage springs
Front: 13-inch disc
Rear: 13.5-inch disc
Assist: 4-wheel ABS w/Dynamic Rear Proportioning
Steering Ratio: 16.73:1 variable ratio
Turning Circle: 47.2 feet
Wheels (optional): 17-inch aluminum
Tires (optional): P265 all-season
Wheelbase: 143.5 inches
Track (front/rear): 68.1/67 inches
Overall Length: 230 inches
Overall Width: 79.9 inches
Overall Height: 73.7 inches
Curb Weight: 5,386 pounds
Payload: 1,714 pounds
Maximum Tow Rating: 9,500 pounds
OBSERVED FUEL ECONOMY
EPA Mileage (city/highway): 14/20
Average Daily Driving,
Non-towing: 16.1 mpg
Overall Towing: 9.8 mpg