Your trans does not have a wide and narrow headset available for it, that's the newer grey trans. Go to Traxxas.com, Products, Nitro and find TMaxx Classic. Then click Downloads for exploded views with part numbers. I can't tell what's wrong there other than your missing the metal ring that bolts to the plastic gear. Also kind of looks like a grub screw laying in there, thats not right. That metal disc (2 speed pawl) has two grub screws, the one that's angled adjust when it shifts into 2nd gear and the other holds the disc onto the shaft. That loose grub screw is likely for the 2 speed adjustment. There should be a spring in the disc, if it's still there just put the grub screw back and adjust after you get the truck running. If the spring is missing you'll need to buy a new 2nd gear pawl assembly n