The Y class has an interesting heritage. The scrapping of swing door suburban trains meant that _M__ motor car bogies were surplus. To take advantage of this equipment it was decided to build a low horsepower shunting locomotive which could also be used on light branch lines.
Eventually seventy five locomotives were built; numbered 101 - 175.
They were an excellent shunting engine; a quick throttle response due to the traction motors in permanent parallel.
They were built between 1963 and 1968 by Clyde Engineering. The prime mover was a V6 567 series, later 645 series engine.
The early units did not feature traction motor blowers. However train service and long hauls up hill saw motors overheat. Traction motor blowers were fitted.
The most unusual feature of the Y class loco's are the two windows mounted just below the roofline at the cab end. The first Y class had these windows mounted as 'shunter windows' below the cab end front windows. The Chief Mechanical Engineer of the time regarded these as too radical and could see that crews would want this feature fitted on other locomotives. The windows were moved up to the roofline and the holes were blanked. Inspection of the first five units showed that holes had been cutout of the cabwork and blanked.
The two characteristic sounds from these locomotives were the V6 exhaust stack noise and the brake rigging rattle whilst in motion. This rattle was generated when loose brake rigging rubbed on worn down wheels which had tread metal overlapping the tyre sides.