It was revealed a few months ago that Forza Mortorsport 4 will have a little something special inside of its content. Namely, they had a Warthog from Halo 4 sitting in the Auto Vista mode which allows players to sit there and look at the cars in any angle that they want to see it from, which while may not be exciting for some is certainly an interesting feature. Plus you can listen to Cortana tell you all about the vehicle!
Though despite its inclusion in Auto Vista mode, the Warthog won’t be playable in the game and Turn 10’s Dan Greenwalt has spoken to Eurogamer about why that is. He said that the technology used for the Warthog simply isn’t available for other cars, like the four wheel turning and all of that. This means that they will need to build the car from the bottom up with all their little specifications which would be “a big investment” to only bring one vehicle to the game. Plus Forza 4 simulates real driving physics on real world tires for all of their cars, and since the tires from the Warthog sport technology from 2525, that just isn’t possible.