The 4000 class were introduced into service in 1999, an initial 38 members of the class were extended by 11 members in 2004.

Designed by Clyde and built by Walkers, these locomotives are the most powerful narrow guage diesel-electric locos in the world. They use the brand new EMD 12 Cylinder 710 G3B engine.

They are very similar to the AWR Q class, but use AC traction equipment as opposed to DC traction equipment, which provides a higher tractive effort.

They can be found mainly working large 84 and 104 wagon coal trains in the Blackwater and Moura basin, but can also be found working the Bowen Basin coal trains and Phosphate trains on the Mt. Isa line (with a 2800 in the lead). The 4000s do visit Brisbane every now and again for wheel lathe attention.