Whenever i run my slash down the street, it is fine up to about 20 mph but once i go higher than that, then the car makes this really weird noise that sounds similar to a fork scraping on a pot. It doesn't happen constantly, just every 5 seconds or so it will do it for just half a second or so. I think it might have something to do with the rear diff because i had to take it apart and clean because sand got in there, and just sprayed wd-40 in afterwards so that might be it. That was probably a stupid idea. If that's it, does anyone know what i should put in there instead?