Hi. The toilet in my 2nd floor bathroom produces a rumbling noise in the ceiling about 1 minute after I flush the toilet. The rumble is up by the ceiling and last about 5 seconds. There is a roof vent for that bathroom and another 2nd floor bathroom (no problem in that toilet) and I shined a flashlight down the vent and there doesn't appear to be any clogs. Any ideas? Thanks.

Could the rumbling noise be being made by the water supply refilling the tank?
Turn off stop valve to prevent toilet refilling then flush.

If you have plastic plumbing on your drain lines this could be the noise the waste water makes falling through the plastic pipe. This is a real draw back from having plastic in a two story house.

Yes, Thanks. The water supply was the problem.. I turned off the supply line, flushed, and it didn't make the noise. Turned it back on, and once the tank filled, the supply line, and fill valve vibrated. The supply valve wasn't open all the way and after I opened it all the way, it reduced the rumble by 90%. I replaced all the insides of the tank because I was having a flapper problem also. After replacing everything, including a new supply line, it works perfectly! Thanks!