Y harness
I'm not into ground based RC, but I have a theory...
Don't RC cars / trucks incorporate springs into the steering mechanism to prevent stripping the servo if the wheels hit a hard bump? I'm not talking about the suspension springs. The weight of the truck may provide enough friction on the wheels to cause the steering springs to compress instead of turning the wheels. Since turning the wheels while the truck is standing still serves no purpose, this sholdn't be a problem, as long as the steering turns as soon as the truck starts rolling. If they don't, try installing stiffer springs.