can i put a exceed .18 motor on my rustler which has a .15 motor? will it make it faster?

the 2.5 in the rustler is plenty powerful for the truck. I don't think you'll see much of a performance increase with the 18

If you exceed 2.5 you will have to modify entire drivetrain.... but, it can be done ... I have a 3.3 in my rustler and it is very fast...
starting out the 3.3 would eat gears and all of rest of drive train.... but it is fun and fast now...

i don't think the exceed .18 would tear up anything. exceed isn't known for top quality, unless they used a sh .18, like they did with the .28 in the mad beast. in that case it should be quite the upgrade, though i believe if your gear mesh is set right, you shouldn't tear anything up. my friend mounted an ofna .28 in his rustler, and it is still running good.

It doesn't have to be modified, just loosen the slipper clutch a bit. The weak link will be the planetary gears. They will need replacement regularly (about every gallon depending on driving style)