In 1980, the SBB had ten heavy class Ee 6/6^II shunting locomotives built. The mechanical part came from SLM Winterthur, while BBC was responsible for the electrical part. It used converter technology, making it the second locomotive of this type on the SBB. Structurally, the Ee 6/6^II was similar to many diesel shunters, i.e. it had a supporting frame, a central driver's cab and lower and narrower superstructures to enable visibility in both directions. There was a pantograph on the cab roof, which was used for driving in both directions.

They replaced the last Ce 6/8^II that were still used in shunting service. They were mainly used for service on electrified humps in marshalling yards. Now and then they also ran freight trains on routes of 100 kilometers and more, for which the top speed of 85 km/h was still sufficient. The career of the locomotives, now known as the Ee 961, ended after a little more than 40 years. By the beginning of 2021, all of them had already been decommissioned and scrapping began shortly thereafter.