THE Astra SRi 2.2-litre engine is mated to heavy duty versions of Astra's five-speed, close ratio manual transmission and optional four-speed electronic automatic. Both use different internal and final drive ratios to 1.8-litre Astras. The automatic features a lock-up torque converter to maximise fuel economy at cruising speeds and has an "overdrive" fourth gear to help towards the same goal. A unique four-point Neutral Torque Axis power train mounting system offers noticeable refinement through decreased vibration and lower engine idle speed. The auto features Economy, Sport and Winter modes and automatically selects neutral at idle to minimise vibration and reduce fuel consumption by up to 3 per cent. The manual transmission shift mechanism is decoupled from driveline movements to prevent lever movement and improve noise levels. The auto features a safety lock, which does not allow the driver to shift out of park unless the brake pedal is applied.