first thing i would try is buy a capacitor like the one spektrum makes to help handle voltage drop outs http://spektrumrc.com/Products/Defau...ProdID=SPM1600 . im not familiar with the RX8 BEC but it seems like you might be momentarily overloading it. its possible that the BEC is not reacting fast enough to increase the current supply.

when you say nothing connected do you mean the servo's are not attached to the steering of the truck?