build a gmaxx and i need help

[JoFreak]

Well...
As I told you in the PM I sent you (you're welcome btw... ) you most likely need to change down to the 10T pinions for the diff.
And that's exactly what I and others told you before you started building your truck: "If you are going to use a CD you will need the pro diffs with the 10T pinions".
As for Brians calculator: just type in all your values and click on "calculate speed".
The tires are in the calculator, so just choose them. You said you run it on 5s lipos, so choose "5 cells" in the according drop down menu and choose 4.2V in the next menu, so you get the absolute maximum on which speed is possible. Enter 2200 for the motor and choose "direct drive or center diff" for transmission.
now you have to enter what combination of pinion and diff you are using, "8th style buggy 43/13" in your case. You can change that later if you want to see what difference it would make to change to the 10T pinions.
Now all there is left to do is enter what spud and pinion you are going to use on the centerdiff. 44T is what I have and what fits into the G3 chassis without problems, 46T would be an option. Don't know the dimensions of the FLM chassis (why is this thread still in the gorilla forum anyways?), but I am pretty shure a 50T spur wouldn't fit.
Now you just enter what pinion you want to use and click "calculate speed" and see how fast it would go...