  The properties of $\gamma$ instability in rapidly rotating even-even
$^{132-138}$Nd isotopes have been investigated using the pairing-deformation
self-consistent total-Routhian-surface calculations in a deformation space of
($\beta_2, \gamma, \beta_4$). It is found that even-even $^{134-138}$Nd nuclei
exhibit the triaxiality in both ground and excited states, even up to high-spin
ones. The lightest isotope possesses a well-deformed prolate shape without
$\gamma$ deformation component. The current numerical results are compared with
previous calculations and available observables, showing basically a general
agreement with the observed trend of $\gamma$ correlations. The existing
differences between theory and experiment are analyzed and discussed briefly.
