[Jared Russell]

Originally Posted by Ozuru

I just changed the testing code to this now and the issue persists. Shouldn't this have fixed it?

package org.usfirst.frc.team2559.robot;

import edu.wpi.first.wpilibj.IterativeRobot;
import edu.wpi.first.wpilibj.RobotDrive;
import edu.wpi.first.wpilibj.Talon;

/**
 * The VM is configured to automatically run this class, and to call the
 * functions corresponding to each mode, as described in the IterativeRobot
 * documentation. If you change the name of this class or the package after
 * creating this project, you must also update the manifest file in the resource
 * directory.
 */
public class Robot extends IterativeRobot {
    /**
     * This function is run when the robot is first started up and should be
     * used for any initialization code.
     */
	
	Talon talonleft0 = new Talon(3);
	Talon talonleft1 = new Talon(4);
	Talon talonright0 = new Talon(5);
	Talon talonright1 = new Talon(6);
	RobotDrive rDrive;
		
    public void robotInit() {
    	rDrive = new RobotDrive(talonleft0, talonleft1, talonright0, talonright1);

    }

    /**
     * This function is called periodically during autonomous
     */
    public void autonomousPeriodic() {
    	rDrive.tankDrive(-0.4, -0.4);
    }

    public void teleopInit() {
    }
    /**
     * This function is called periodically during operator control
     */
    public void teleopPeriodic() {
    	
    }
    
    /**
     * This function is called periodically during test mode
     */
    public void testPeriodic() {
    
    }
    
}

RobotDrive by default inverts the command to your right side drive motors (the authors assumed you'd wire red to + on both sides), so calling tankDrive(-.4, -.4) actually sends -.4 and +.4 to your Talons.

tankDrive(-.4, .4) or visa versa should result in identical pulsewidths.