Coastdown time (CDT) monitoring of power driven rotating systems during every routine stoppage, using the coastdown phenomenon (CDP), is investigated for prediction of onset of failure. CDP plots were made for a variable speed motor with oil, multipurpose grease and Servogem grease lubrication, with released carbon brushes and with various misalignments, each at four cut-off speeds. Results facilitated determination of transition speed by sudden increases and decreases in deceleration on a deceleration versus speed curve of a CDT study. Decrease in CDT after reassembly of the rotating system indicates deviation from correct alignment. Dry friction arising from carbon brushes increases deceleration rate considerably. © 1988.