GM 4L30-E (A4S270R) transmission. Six-cylinder pre-facelift cars built for the Japanese market were fitted with the Jatco 5R01 5 speed automatic transmission. All other six-cylinder models were fitted with 5-speed transmissions, either the GM 5L40-E (A5S360R), GM 5L40-E (A5S390R), or ZF 5HP19 (A5S325Z) transmission, depending on the year and model. V8 petrol models were fitted with either the 5-speed ZF 5HP24 (A5S440Z) or the 5-speed ZF 5HP30 (A5S560Z). Differential ratios The following differential ratios were used by the E39: 2.35: 530d manual 2.64: 525tds automatic 2.81: 540i manual, 530d automatic 2.93: 528i/530i manual 3.07: 528iT/530iT manual 3.15: 525i/525tds manual, 540i automatic 3.15 (LSD): M5 3.23: 525iT manual 3.46: 525i/528i/530i (5-speed) automatic 4.10: 528i (4-speed) automatic Steering Unusually, two different steering systems were used for the E39, depending on the engine. Models with four-cylinder and six-cylinder models use rack and pinion steering, the first time this system has been used in a 5 Series (except for the E34 525iX model). This system steers from the front of the axle. Models with V8 engines use recirculating ball steering, as per the previous generations of 5 Series. Chassis and body Compared with its E34 predecessor, the E39's wheelbase grew by and overall length by . Torsional rigidity was increased over the E34 by 40 percent, which reduces body flex and allows the suspension to operate more accurately, also improving ride quality. Structural dynamics were also an objective of the body design, so the body's frequencies for torsional twisting and bending are in separate ranges and above the natural frequency of the body. These frequencies are out of the range of engine and driveline vibrations, to avoid vibrations being amplified. Due to a stiffer body shell, the weight of the chassis increased by , which is offset by the reduced weight of some aluminium suspension components. The wagon version was longer than the previous generation (E34) and weighed approximately more. Suspension The E39 was the first 5 Series to use aluminium for most components in the front suspension. The proportion of chassis components using aluminium significantly increased for the E39. The front suspension consists of a double-jointed version of the MacPherson strut, with six-cylinder cars using an aluminium front subframe. Aluminium is used for the steering knuckles, outer strut tube and the spring pads, resulting in a weight saving of . V8 models also use aluminium in the steering box and several suspension links,