Flexible and cost effective modular system
The modular concept of the Tractive gearboxes is being used since 1995. It allows us to use the same or very similar parts for both rear- and front wheel drive transmissions. The shift mechanism, type of ratios, dog rings and associated parts, as well as many other parts, are the same for both the RD90 and the SD90 gearboxes.
Differently shaped casings can be produced using the same or similar fixturing, independently of the car make. CAD/CAM programming considerably cuts lead-time for the development a new gearbox casings. This is a very cost-effective concept for the manufacturing of gearboxes in relatively small numbers.
Unique housing and layout
The basic layout of the RD90 / SD90 gearboxes is unique, eliminating all problems related to thermal and mechanical properties of traditional layouts. All components used for the housings are machined from billets of air craft quality aluminium (590N/mm2 UTS), to form light and very rigid units.
The main housing of the SD90 casing is, basically, a fully-machined piece of aluminium billet, combining minimum weight with superior mechanical, dimensional and thermal stability.
Most of the other parts are bolted to the main housing to form a complete casing. The gear set is enclosed in a housing which is completely round on the inside. On the outside 12 flats have been milled out for weight reduction. The torsional forces are optimally absorbed. The logical load-path for the bearings minimises deflection and maximises the gear load-carrying capacity.
When gears are meshing and working with each other on rotating shafts, the shafts will bend. When the gearbox warms up, components expands differently. With a symmetrical, cylindrical housing and symmetrically placed shafts, as in the Tractive gearboxes, the effects of this thermal expansion are minimized.
Another very important advantage of a cylindrical housing is that the pumping losses are dramatically reduced as the oil splashes around much easier, without much constrain. All in all, lubrication is more efficient and losses are smaller.