Fuel pump sender problem

I replaced my rear fuel tank and the fuel pump a while back. After replacing it, whenever I went around a sharp curve while driving and running off the rear fuel tank, the fuel gauge indicator would swing left or right depending on the direction I turned. Sometimes the fuel gauge indicator would pin all the way to the right off scale and stay there until I made an opposite turn.
I've had need to remove the tank and fuel pump today and would like to fix the problem while I have everything taken apart. Does anyone know what is supposed to keep the fuel pump float mechanism from moving when you drive the truck? I'm wondering if I lost a piece when I replaced the fuel pump.
Thanks

Permanent internal fuel cell(tank) baffles.