99 AM General Hummer
Traction-Control For Our Favorite Ballistic Behemoth
The Hummer has been available for public consumption for nearly eight years. So one may expect the drool and gawk factor among civilians to be relatively nonexistentespecially in Los Angeles. Not so. Were amazed every time we test one of these burly beasts how many people still stare, point, and pull their younguns away from the curb in fear.
AM General sells less than 1,000 vehicles per year to the public, and with an as-tested price tag of $83,149 for our loaded four-door open top, Hummers have the status of certain Ferraris, Porches, and Bentleys. They have the ability to endow the average man with instant celebrity. But weve always been more impressed with the Hummers four-wheeling capability than its restaurant valet cachet. And increasing the Hummers four-wheeling capability is exactly where AM General concentrated its improvements for 1999.
Although the rugged and unique drivetrain remains for 1999, AM General has developed a new ABS/four-wheel traction-control system that endows the Hummer with the four-wheeling ability of locking differentials without the on-road drawbacks. Hummers have always had the torque-sensing Zexel-Torsen limited-slip differentials in both front and rear axles, but while their operation is smooth, limitations are apparent when Hummers encounter extreme low-traction conditions. AM Generals new Torq Trac 4 (TT4) traction-control system combines with the Torsen limited-slip differentials to provide torque to the wheel(s) that has traction. The system is very similar to the one used on the new Land Rover Discovery Series II. Basically, ABS wheel sensors detect wheel speeds and generate signals transmitted to an Electronic Control Unit (ECU) that decides which wheel requires braking forces and sends it via a hydraulic pump. The TT4 system limits wheelspin during acceleration and automatically transfers torque when any wheel loses traction. If the TT4 system is active for more than 60 seconds, it will deactivate and allow the brakes to cool for an additional 60 seconds.
It's complex, but our experience is that the TT4 system performs reliably and always seems to enable forward progress, even when just one tire has traction.
The only engine offered for 1999 is the 6.5L Detroit Diesel turbo-diesel V-8 that now generates 195 hp and 430 lb-ft of torque. Power is channeled through a GM 4L80E four-speed automatic to an NVG 242 transfer case that splits power to hypoid-type differentials housing 2.56:1 gears. The 1.92-geared hubs increase the Hummers crawlability to a ratio of 33:1. While the diesel doesn't provide brisk acceleration, it does gather speed better than previous motors and works well with the gearing during highway passing maneuvers. The four-wheel independent suspension combined with our optional mild-tread Goodyear Wrangler GSA 37-inch radials offered a decent highway ride, especially considering the beast's 2-ton load-carrying capacity.
Overall, we were impressed with the traction improvements to the 99 Hummer. While we didn't run the Rubicon or Sledgehammer with our test unit (hey, it's a borrowed $83,000 4x4), the big beast was able to traverse some fairly extreme off-camber notches that would have stopped non-TT4-equipped units. For those who can afford it, the Hummer gives an empowering driving experience that can be matched by few vehicles. And with the new traction- control system, that experience is only intensified.