No, it's not junk. The T-Maxx gets a really bad rap sometimes, but they really are some fun trucks for their intended purpose. Heck, I keep mine around so I can have something to bash with when I'm not racing. My 5 year old really likes it too...

If you're looking for the strongest, fastest, highest jumping rig out there, then it's maybe not the best, but if you're just wanting something to have fun with, it's great. Parts are available just about everywhere, and aren't that expensive, so keep it and enjoy yourself.

Regarding your engine, since it's used, the first thing you should do is pull it out of the truck, strip everything down and clean it. That's also a good time to check the clutch and replace the clutch bell bearings (which may be the rattling sound you're hearing). While you have the piston and sleeve out, try to gently push the piston up to the top. If you can get it near the top of the sleeve, it's worn out, and needs to be replaced.

If it is worn out, you can either make use of the Traxxas engine replacement program, which will be about $100 for a new motor, or go a better route and put an OS .21 TM in it. It's a much better motor, but also will cost more. If the motor is good, just clean everything up, put it all back together, and try tuning it using the method listed in the tuning bible in the nitro engne section.

Either way, have fun with your new truck....