1999 Hummer Model Year Changes.

1999 saw some significant changes for the Hummer. Government regulations required the Hummer (which is a class III Truck) to have ABS for the first time. Unfortunately the Torsen differentials and the Brake/Throttle Modulation (BTM) Technique that made them so effective off-road were not compatible with the required Anti-lock Braking System. The solution to keeping the Hummer's Off-road prowess and complying with the regulations was Torque Trac 4 or TT4. This electronic system preforms a version of BTM but without driver participation. When wheel spin is detected, brake is automatically applied to the spinning wheel and torque is transferred to the wheel with traction. The new Torsen II differential works much the same as the old Torsen but with less torque bias. Manual BTM still works on the '99 Hummers but is not as effective because of the lower torque bias. Some owners love the TT4 system while others prefer the old system of manual BTM .

Powertrain and Identification Information. VIN 10th Digit designating year = "X" Engine: 6.5L Turbo Diesel 195 H.P. 430 lb. ft. VIN 4th digit ="Z" 4L80E Electronic 4 speed Automatic Transmission. VIN 5th digit ="A" Top Speed 83+ mph. 831 '99 models built.

Significant changes for 1999. 6.5L Turbo Diesel Standard. 6.5L NA Diesel no longer available. First Year for Anti-lock Braking System (ABS) First Year for TT4 Traction control system. TT4/ABS Video Click Here. New Wiring Harness. New fuse relay center. CTI pump moved to new location. Accessory fuse panel added. New Power Steering Pump & reservoir. New Power Steering Cooler. New Water Pump. Torsen II differentials. New halfshafts with tone ring for detection of individual wheel speed. New 4 Button remote entry. New heated windshield glass. New larger winshield washer reservoir. New Color Night Storm. New Color Mesa Dusk. Green Metallic discontinued.

Valuable upgrades to look for in a '99. Although steering components were upgraded several times by '99, the factory "Problem Solver" Idler and Pitman arms introduced in later years are much more durable than those on a '99.

'99 Specifications, options & Prices:

Available colors:

Mesa Dusk (C22). New Color for '99.

Night Storm (B21). New Color for '99

Competition Yellow (Y20).

Candy Apple Red (R19).

Silver Metallic. (S15)

White. (W8)

Black. (B9)

Bright White. (W14)

Although most factory custom colors show up on emergency vehicles and as factory tests, custom colors were available on all Hummers for an additional $1,000 charge. Below is an example of a Hummer with a factory experimental color (X), Cactus Green. Cactus Green never made it into full production.

Body Styles Available in '99:

HMCS. 4-Passenger Wagon

HMC4. 4-Passenger Hard Top

HMCO. 4-Passenger Full Door Open Top.

XLC2. 2-Passenger Hard Top Enlarged Cab.

TOTAL PRODUCTION COUNT BY MODEL AND COLOR. "X" Colors are "Experimental" or special order, often seen as production colors in later years.

COLOR FULL DOOR OPEN TOP (HMCO) WAGON (HMCS) HARD TOP (HMC4) 2-PASS. ENLARGED CAB (XLC2) TOTAL B21 (Nightstorm) 11 27 7 1 46 B9 (Gloss Black) 69 147 44 3 263 C22 (Mesa Dusk) 38 65 15 1 119 R19 (Candy Apple Red) 34 50 14 3 101 S15 (Silver) 12 33 12 1 58 W14 (Bright White) 28 58 15 15 116 W8 (Gloss White) 9 7 2 1 19 Y20 (Competition Yellow) 49 27 11 87 X02 (Safety Green) 1 1 X20 (Gloss Red R7) 5 5 X28 (Green ) 1 2 3 X29 (Gloss Green (G10) ) 1 2 3 X30 (Blue) 6 6 X31 ( Firetruck Red) 1 1 X32 (Green) 1 1 X33 (Pewter) 1 1 Tan Interior 114 165 35 314 Gray Interior 138 261 85 33 517 Cloth 220 401 108 20 749 Vinyl 32 25 12 13 82 TOTAL 252 426 120 33 831

© Copyright 2004 Jim Lynch.