Coupling rod
![Connecting rod and coupling rods attached to a small locomotive driving wheel](/Images/godic/202501/06/Wheel_of_locomotive5128.jpg")
![Hinged side rods connecting the driving wheels of a 4-8-4 locomotive.](/Images/godic/202501/06/MILW_261_drivers5128.jpg")
![Counterweight on a small outside-frame dual-mode Electro-diesel locomotive, a Swiss Tem II shunter.](/Images/godic/202501/06/Roues_de_Tem_II_288_à_la_gare_du_Pont_18-08-2012_45128.JPG")
A coupling rod or side rod connects the driving wheels of a locomotive. Steam locomotives in particular usually have them, but some diesel and electric locomotives, especially older ones and shunters, also have them. The coupling rods transfer the power to all the wheels.