  With focus on the cosmological evolution of linear perturbations of matter
and geometry, we calculate the equivalent expressions to that of the Newtonian
and Synchronous gauges within the framework of Unimodular Gravity, being these
two gauges commonly used and implemented in Boltzmann codes. An important
aspect of our analysis is the inclusion of the energy-momentum current
violation, as well as its perturbations. Moreover, for the first time we
demonstrate that it is possible to fix both gauges consistently, although as it
has been already noticed in previous literature, neither of them is recovered
in the sense of the dynamics given in General Relativity for matter and metric
fluctuations. Specifically, we show that since the unimodular constraint at the
level of linear perturbations lead to only one degree of freedom of scalar
modes of metric fluctuations, the dynamics in Unimodular Gravity forces to keep
the anisotropic stress in the Newtonian gauge, whereas the cold dark matter
comoving frame can not be set in the Synchronous gauge. The physical
implications on the density contrast of cold dark matter is reviewed, and the
Sachs-Wolfe effect is obtained and compared with previous results in the
literature of cosmological perturbations in Unimodular Gravity.
