i'm not sure but i did mine to be on the safe side. if there happened to be someone new in the manufacturing plant and is still learning to put the car together theyt might not get exactly right. but it's pretty easy to do. i think you should do it, this way you know it's right, and you won't have to worry about it. it only takes a couple minutes to do it. ok it took me a couple minutes but i'm new to nitro rc's.
and like every one will tell you blue loctite is a must. adjusting the clutch to spur gear may seem a little nerve wracking but it's not that bad. if you follow ehroof's advice you'll get it right, he won't steer you wrong.