A considerable number of the T 478.3 or class 750/753 diesel locomotives, built in the seventies by ČKD, were later rebuilt with Caterpillar engines. The most numerous variant of these rebuilds is the class 753.7 with more than 100. They were rebuilt between 2008 and 2010 by CZ Loko and the only parts which remained were the frames, the body and the bogies. The old 1,800 hp ČKD engine was replaced by a 2,100 hp Caterpillar 3512 B DI-TA. This now transmitted its power via a three-phase alternator and rectifiers. The cooling system was completely renewed and a dynamic brake was added. Additionally, the cabs were now more modern and air-conditioned. Customers for this variant were ČD Cargo, PKP Cargo and several private operators in the Czech republic and Italy. Other rebuilds were the ČD classes 750.7, 753.6 and 755 and the ZSSK class 756.