The flavor changing top decay t-->c+sneutrino or sneutrino-->t+c(bar) in the MSSM without R-parity

Widths for the new flavor changing top quark decay t-->c+sneutrino or for the reversed sneutrino decay sneutrino-->t+c(bar) are calculated in the MSSM without R-parity conservation. For large \tan\beta, e.g., \tan\beta ~ m_t/m_b ~ 40, Br(t-->c+sneutrino) > 10^{-5} or Br(sneutrino-->t+c(bar)) > 10^{-6} in a relatively wide range of the supersymmetric parameter space as long as there is more than one non-zero R-parity violating coupling. In the best cases, with a typical squark mass around 100 GeV, we find that Br(t-->c+sneutrino) ~ 10^{-4} - 10^{-3} or Br(sneutrino-->t+c(bar)) ~ 10^{-5} - 10^{-4}. For \tan\beta ~ O(1) the corresponding branching ratios for both top or sneutrino decays are too small to be measured at the LHC. Therefore, the decays t-->c+sneutrino or sneutrino-->t+c(bar) appear to be sensitive to \tan\beta and may be detected at the LHC. The branching ratios of the corresponding decays to an up quark instead of a charm quark, e.g., t-->u+sneutrino or sneutrino-->t+u(bar), may also be similar.