My toilet bowl fills up with soap suds when the washing machine (on the other side of the wall) runs. It also flushes extremely slow on occasion. I've tried to run a drain snake through the clean out, but can't get it into the pipe properly. I am on a septic system.

A "gurgle" indicates a blocked vent. The sound you hear is the fixtures attempting to vent through the traps. The solution would be to snake from the lavatory roof vent. Put out enough snake to reach the base and 16 feet more. Flush with several pails of hot water. Good luck.

John

Open up the house cleanout and cycle the washer. Is there a back up from the clean out? If so have the tank pumped. If no back up then you have a partial clog in your drainage downstream from the bathroom. Follow Johns advice,
The solution would be to snake from the lavatory roof vent. Put out enough snake to reach the base and 16 feet more. Flush with several pails of hot water. Good luck and thanks for rating my answer. Tom