Model # FTF530FS1
, the unit would make a thumping noise during the spin cycle, but sounded OK during agitation. After removing the rear panel, I was able to observe the drive pulley make a visible jerking motion on each rotation. I removed the belt and was able to feel some play between the pulley and shaft of the drum assembly, and bits of metal filings. With the bolt securing the pulley to the shaft, there should be no movement between these two pieces of metal. So I replaced the pulley with a new one and now it sounds normal.
Frigidaire Washer Pulley Part # 131883400