The present invention concerns a crosslinkable silicone elastomer composition and a method using the composition according to the invention for forming sealing gaskets and assembly seals for the components of a powertrain. The silicone elastomers prepared from the composition according to the invention have: good mechanical strength properties such as shore hardness, breaking strength, modulus at 100% elongation and good resistance to ageing in chemically aggressive fluids such as those used, for example, in a powertrain, in this case engine oils, lubricants for the gearbox and axle, oil/petrol mixtures, coolant liquids, fuels or antifreeze liquids, and good adhesion properties even on surfaces polluted by oils used in a powertrain.