I am trying to use a 30:1 Metal Gearmotor 37Dx52L mm with a 6 volt (actually more like 5 volt) source. I am using a sabertooth 25 amp DC motor controller paired with an arduino. I did not order, research, or decide on these products, rather they were given to me with the project description. It seems the motor has very little torque with the 5 volts supplied. It is only being used as a steering drive for one of those toy cars that children sit on and ride in. Right now there is no load on the car other than the car itself and the motor is not capable of turning the wheels on carpet, and is very very sluggish on tile. Could it be because the source voltage is too low?
I suspect that your Sabertooth motor controller can output more than 5V; you might do some research into the parts you mentioned, since their specifications will be important to your project.
Those 37D gearmotors have both 6V and 12V ratings listed under the “Specs” tab of their product page. Please note that torque has a linear relationship to the input voltage, so the torque at 6V is about half that at 12V.
However, I do not expect those gearmotors to perform well with a load that large even if the input voltage is increased. As a general rule of thumb, we recommend running our motors are somewhere between 20% and 30% of the rated stall torque. You should probably look for larger scale motors that can handle more torque than the ones we carry. Additionally, we do not recommend our products be used in systems when their failure could result in injury or property damage.