I was recently promoted and now too much work is getting dumped on me.

I was recently promoted and now too much work is getting dumped on me. Based on what I've seen on my team, and conversations I've had with teammates, I am being asked to do work well above my pay grade. My manager has said multiple times I should be at at least the level above where I am right now, even with this new promotion. However, my manager will not be able to advocate for me for long as they are leaving the team soon. There has been a lot of turnover on our team recently, probably for a variety of reasons, so I am feeling very overwhelmed by what I am being asked to take on and there is little regard for the fact that I simply do not have the appropriate compensation/title for what I am being asked to do. I initially saw this as an opportunity to grow and move up to where I should be at, but the way the company works I won't see a promotion for at least another year, if not more. How can I approach this situation? Thank you in advance for the advice.