I'm not sure how many of you are aware but this game, as realistic as it is in many ways, is quite flawed when it comes to simulating engine speed & sound. In the cabin view the tachometer actually displays engine load rather than engine speed. When you shift to a higher gear, RPM should go down but in this game it often goes up as the engine load increases in the higher gear. And going downhill while in gear the engine should be revving as the truck's momentum keeps the engine turning but in this game the engine is essentially idling, even though it's providing good braking.
Can this get fixed? It's not a huge flaw, but it is physically wrong. I hope at least MR2 simulates this better.