Inside the car, there is no change in overall appearance. The seat foam has been improved, seat tracks have been redesigned to add one inch of additional rearward travel to better accommodate taller drivers, and seat belts have been attached to the seats to move with them. There's a new six-way power driver's seat, replacing the four-way, along with new fabrics and sew patterns in cloth and optional leather. Embossed ponies on the upper portions of the seat backrests give the interior a sporty, traditional Mustang look. Medium graphite, medium parchment and midnight black are the new interior colors. The instrument panel, the center console and the headliner will be color keyed in 1999 models, instead of the former black-only.
Audio systems have been upgraded for the second straight year. The 80-watt premium sound system that comes standard on all models is combined with new, better-sounding speakers. An optional CD/radio combination, a CD/cassette system, and the Mach 460 system will continue for 1999.
The interior is nice and cozy in the coupe. Now there's enough seat track length to accommodate tall drivers and just enough elbow room to keep from feeling cramped. The Mustang's back seat is vestigial at best, with only enough room for small objects or very small people. The split fold-down rear seat is handy for hauling large cargo, however.
Acceleration performance is improved for 1999. Power from the Mustang GT's V8 engine is up 35 horsepower (and 10 foot-pounds of torque) over last year. The GT's revised 4.6-liter sohc modular V8 engine produces 260 horsepower at 5000 rpm, with 302 foot-pounds of torque at 4000 rpm. The engine features new camshafts, new intake manifold runners, and larger valves, for improved air flow above 3000 rpm. A new coil-on-plug ignition system replaces the previous distributorless system for higher energy spark.
Power from the standard 3.8-liter split-port V6 engine is up substantially as well, rising from 150 horsepower to 190 horsepower at 5250 rpm with 225 foot-pounds of torque at 3000 rpm.
The drivetrain has been improved with a recalibrated 4-speed automatic transmission for smoother upshifts. The 5-speed manual transmissions are carried over from 1998, with the V6 using the T-5 and the V8 using the T-45, both now sourced from Tremec. All models, regardless of engine or transmission, get a 3.27 :1 rear axle ratio. Both gearboxes shift smoothly and mate well to an engine that features a flexible powerband and sufficient strength to take high-rpm shifts for the life of the car.
Traction control is a new option for 1999. The Bosch system works at all speeds to reduce wheelspin. Whenever wheelspin is detected, the system retards ignition timing, cuts fuel flow, and activates the brakes at one or both drive wheels, in that order. The driver can turn the system off with a console switch.
Most of the raw edges and choppiness of the Mustang's old suspension behavior have been smoothed out. Engineers retuned the rear suspension for improved compliance by increasing suspension travel. This reduces ride harshness. The GT now has linear-rate springs, up in front to 450 pounds per inch. At the rear, the old springs were swapped out in favor of 210 pound per inch linear-rate springs. These decrease the Mustang's well known ride stiffness and improve steering feel and response.
The steering is more direct and more positive than previous Mustangs. A revised boost curve gives the steering more linear response and better on-center feel. The turning circle has been reduced by three feet through changes to the steering rack, the lower control arms and front stabilizer bars.
The braking system got a thorough going-over, which it needed badly, with new aluminum twin-piston front calipers that not only whack 10 pounds off the front of the car, but also result in much improved pedal feel. A new master cylinder design offers an improved brake pedal ratio of travel to brake force and improved pedal modulation. ABS is still optional for 1999 and must be ordered to get the traction control system.