The L1s and L2s were unstable at higher speeds due to the lack of effective cross-balancing,[1] making the 4-wheel leading truck simply a better distributor of their weight; the L1s and L2s were consequently limited to 60 mph (97 km/h), though this issue was resolved for the L3s and L4s using data gathered from two experimental L-2s.

They would be equipped with the appropriate accouterment of the time; kerosene headlights, straight running boards, full pilots, Cole trailing trucks, and in some cases Russia iron boiler jackets.

These engines were built with clean lines and a notable lack of appliances, though they would be modified extensively in the coming years.

As with the tenders, the earlier L-1s would later be fitted with feedwater heaters, with the majority sporting Elesco bundle-type and Coffin internal feedwater heaters, though a handful of examples on the subsidiary Peoria & Eastern (as well as one on the NYC proper) had open-cycle Worthington SA type units,[3] and one each were furnished with the Elesco coil type (#2503)[4] and the external Coffin variety.

[5] One modification to the L-1s made in the 1920s was the installation of mechanical stokers, mostly of the duplex type, which were fitted universally, easing the job of the firemen.

Gradually, as the L-2s rolled off ALCO's production line in the 1920s, many of the L-1s were displaced, with most of them stationed on the Central's Pennsylvania Division.

As a consequence of the Great Depression and the associated decline in freight traffic, some were retired permanently or put into long-term storage.

They were substantially more powerful than the two-cylinder models, but it was debatable if the additional maintenance requirements of a third, central cylinder, valve gear, main rod and crank axle were worth the performance boost.

These were more modern locomotives than the L-1 class with wide boilers, long tenders, and fitted with feedwater heaters (mostly of the Elesco type and generally mounted in front of the smokebox at the top).

Two L-2 locomotives were given modifications for dual service work: higher boiler pressure, smaller cylinders, lightweight reciprocating parts, dynamic counterbalancing of the drivers, roller bearings on all axles and so forth.

The L-4s were versatile locomotives, with 72" drivers, and worked the heaviest freight and passenger trains during World War II.

The L-3 and L-4 classes had large tenders riding on two six-wheel trucks that were almost as long as the locomotives hauling them, and were mostly coal space with a capacity of 43 tons; water was taken en route using the tender scoop from track pans and thus the locomotives did not need to have a large on-board water capacity.

3001, is a 1940 ALCO-built L-3a at the National New York Central Railroad Museum in Elkhart, Indiana and is the largest surviving NYC steam locomotive.

The tender for L-3b 3042 was converted into a canteen and was used with Reading T-1 4-8-4 2101 during its 1976 tour with the American Freedom Train, as well as with the Chessie System Special.