Many (not all) E-44 locomotives have what appears to be a shunt attached to the individual journals from the truck sideframe on the left side of the locomotive only. This does not appear to be a universal application. What was its purpose: a shunt for cab signals or for propulsion return current?
Neither. Those are speed recorders, used for wheelslip control circuits. Some diesel and electrics had them on each axle, usually on one side of the engine, others only had a single one, usually underneath the cab.
Stuart