The TransSyberia Rally is a rally raid race held in Syberia. The rally is open only to 4WD automobiles and trucks. Technical modifications are allowed, but vehicles must be street legal. Most modifications are to improve safety, reliability and ease of maintenance.
Porsche Cayenne S Transsyberia
The Porsche Cayenne S Transsyberia power unit is virtually unchanged from the Cayenne S – the output of the Transsyberia edition is 4.8-litre natural aspiration V8 with direct gasoline injection remains 385 bhp (287 kW) at 6200 rpm which is connected to a six-speed Tiptronic S with a 4.11 final drive ratio. The technological enhancements include Porsche Traction Management – which is further improved by a transverse lock from the optional Offroad Technology Package (available to regular customers), Porsche Dynamic Chassis Control – which is preset to a “Special Offroad Mode” which allows the Cayenne to pass through bodies of water up to 30" deep, and Porsche Active Suspension Management. The remaining modifications are more rally car-specific.
- Reinforced A and B pillars
- Bolted-down safety cage
- Stronger underbody protection with diamond-plate steel flooring
- Handbrake instead of the standard foot-operated parking brake
- Lightweight sport exhaust
- Roof-mounted snorkel
- Off-road tires
- Roof lights
- Front-mounted winch
- Rerouted electrical system
- Passenger-operated navigation system
The interior of the car is stripped down to the essentials to make room for the dual spare wheels and tires, and the two reserve fuel tanks which occupy what used to be the rear seats. 
In 2007, the TransSyberia Rally stretches from Moscow, Russia to the Mongolian capital of Ulaanbaatar. Participants are in the for the experience of a lifetime as the 6,600 kilometer route crosses the Ural Mountains, winds through subarctic forests and goes up the rugged peaks of the Altai Mountains. The endurance of both man and machine are tested as the route continues across the sprawling Mongolian plains and through the Gobi Desert. 
25 of 34 registered teams will be driving Porsche Cayennes – the Porsche Cayenne S Transsyberia Edition. These vehicles contain numerous modifications to improve the car’s stability, handling and safety, and were built exclusively for the TransSyberia Rallye.
- Porsche Cayenne S Transsyberia: factory-built rally machine - Autoblog
- Rod Millen takes Transsyberia Rally 2007 - Autoblog