Many were later converted for push–pull operation with diesel locomotives, finally being withdrawn when displaced by the electric Dublin Area Rapid Transit service in the mid-1980s.

The first single-unit diesel railcars in Ireland were introduced on the narrow-gauge County Donegal and Clogher Valley railways in the early 1930s.

[2] Early in 1948, the GNR(I) ordered a fleet of 20 railcars, capable of operating in pairs with one or two intermediate trailer cars, from AEC.

[4] However, the success of the GNR(I) cars and the 1948 Milne Report's recommendations in favour of railcars (but not diesel locomotives) encouraged the company to place a large-scale order with AEC in September 1950.

)[7] In 1951, CIÉ ordered a series of 60 cars similar to the GNR(I) examples, again combining AEC engines and Park Royal bodywork.

[8] These vehicles were almost identical to the GNR(I) units but incorporated improvements derived from experience with the latter; most notably, up to four power cars, rather than two, could operate in multiple.

However, the cars' bodywork was constructed at CIÉ's Inchicore Works to a distinctive design by the company's Chief Mechanical Engineer, Oliver Bulleid.

One of them was, additionally, fitted out as a driving trailer, with a guard's compartment at the non-cab end and a large area set aside for prams.

Two further driving trailers, known as "mules," were converted from 1953-built hauled stock but were used only briefly, working as part of the Westport portion of a Dublin–Galway/Westport train.

[17] The 2600 Class were effectively identical to the GNR(I) cars in overall configuration, having a full-width driver's cab at one end, a gangway at the other, and underfloor engines.

[23] When originally delivered, the railcars were employed on mainline express trains, including crack workings such as a three-hour nonstop service between Dublin and Cork.

Eight-car formations were commonly deployed on these duties, sometimes splitting en route to serve (for example) Tralee and Cork or Galway and Westport.

As early as 1968, the AEC engines were considered obsolete, and spares were "virtually impossible" to obtain, forcing CIÉ to cannibalise some of the 2600s to keep the remainder running.

[30] In late 1974, eight cars were reportedly being kept operational to address a shortage of locomotives "by reason of damage by accidents and bomb incidents.

In 1971, with the process of modifying railcars for suburban operations still underway, work began on the first conversions to push–pull stock for service with the then recently re-engined 201 Class locomotives.

The conversion was intended to address both the cars' poor power-to-weight ratio[23] and the increasing difficulties in obtaining spare parts for their engines.

[46][47] The push–pull sets were "not very attractive and were not very comfortable", particularly due to ride problems arising from the vehicles' reduced weight compared to the original railcars.

However, the shuttle was withdrawn in mid-September 1987, due to the poor condition of the rolling stock (the service was resumed at the end of October, using an 80 Class train hired from Northern Ireland Railways).

Iarnród Éireann's first order of diesel multiple units, from Tokyu Car Corporation of Japan, received numbers in the 26xx series when delivered in 1994.