I added a bathroom and laundry room in my basement not too long ago. Due to the height of my existing sewer drain, gravity drain was not an option. Instead I added a grinder pump and connected into the existing drain line. The pump has a separate 2 inch vent pipe which exits the house just above the foundation. What is happening is that when the pump turns on, the first floor tub gurgles and the sewer smell is pretty strong. The grinder pump is connected to the same drain line as the tub, just further downstream. I have no other issues with sewer gas except when that pump kicks on. Suggestions?

You may need a relief vent between the pump and the tub connection on the shared sewer.

Gurgling usually indicates a partially clogged drain line, but we cannot tell if you connected the pump to the system properly, because the vent line exiting a side wall indicates something less than a professional installation.