We conducted internal friction (IF) and elastic modulus measurements on several manganites in the temperature range 100.500 K. The La_1-xCa_xMnO₃ series, with x=0,0.1,0.2,0.33 and 1, was studied showing the magnetic phase transitions and two additional IF peaks around 320 and 400 K, respectively. Both, peaks associated to relaxations, present activation enthalpies of 2.3 and 3.6 eV, whose intensity depends on x. In this work we associate the 400 K IF peak to a Zener relaxation of the cations that occupied the same crystallographic site. We believe that the 320 K IF peak is due to different crystalline states of the samples.