I know there are a ton of threads on this but I can't figure out what I bought on ebay! It is a tmaxx with a 3.3... had chevron tires on it, has grey receiver box, battery box and trans. 12 inch wheelbase also. Has 2.4 ghz controller with reverse switch but no reverse on truck. It has blue aluminium chassis and there is an oval cut out under exhaust. Please help!

I don't know the model number but it sounds like the model of 3.3 before the current extended chassis version that's out now. This model has the same diffs and drivetrain as the current 3.3, the same trans internals, etc, just on the shorter chassis and with grey bulkheads, skid plates, boxes and trans.

With these trucks it's very possible it's not original and has had parts added to it though. The driveshafts, axles and knuckles should be obvious to tell if they're 2.5 or 3.3 spec. In my opinion one of the more important parts is the diffs. 3.3 spec have 4 screws on the outer diff case, 2.5 only have 2 screws at the front or back. It doesn't really matter what model of truck you have though. It's only the internal gears that don't interchange but diff assemblies, the trans do and virtually everything else can be swapped around between versions too.