It however continued to provide Road Motor Services in the Irish Free State which included the operation of several long established cross-border bus services which were unaffected.
In the early thirties the "canny" Mechanical Engineers of the GNR men like George Howden, Dick Meredith, Bobby Pelissier and Johnny Owens experimented with various makes of diesel engines (then known as oil engines) in preference to the relatively short life achieved with the standard petrol units as fitted in AEC Reliance's, Leyland Lion and Tiger buses. Many of these vehicles were retrofitted with a variety of diesel engines at Dundalk Works from a range of manufacturers such as AEC, Beardmore, Dorman, Gardner and Leyland. 1935 arrived and the GNRI had finally and firmly decided that the Manchester built Gardner four and five cylinder diesels were to become the company standards.

1937 was a landmark year for the GNR as the decision to produce its own Gardner engined buses at Dundalk Works became a reality with the roll out of the first batch of a run of 96 buses. This aspect of the GNR is dealt with in another part of this website.