The impact of Pd and Cu substitutions in the Co sublattice on structure and magnetic properties of the 5f-band metamagnet UCoAl was studied. The solubility in the UCo1-xTxAl system has been found to extend up to x = 0.40 for T = Pd and x = 0.10 for T = Cu. In the common solubility range, a very similar development of lattice parameters and magnetization behaviour has been observed for the two systems. Both lattice parameters, a and c, increase linearly with increasing x whereas the metamagnetism is gradually suppressed (the metamagnetic transition is shifted to higher fields and the magnetization in the metamagnetic state is diminishing). The metamagnetic transition vanishes for x≈0.08 similar to doping UCoAl by other elements with more populated states in the d-band than Co (T = Ni and Pt).