MAZDA ALLEGRO 2004 SUSPENSION PROBLEM

Friends, they help me with this inconvenience that I have please.
When I pass by small bumps it feels like a sudden fall and as dry, it takes it to the mechanic and made me change the entire part of the shock absorbers (suspension) and other pieces that go together, but the problem persists, I do not know what Serra, since it spends a lot on the change made.
I also have a problem when the change passes it from 2 to 3rd, it begins to move (staggered) from the rear.

Friends help me since I don't know what it will be. Could the tires, motor, or what?

I don't believe because it would fail to be detained and in motion, if it is a serious suspension that you told us that it was eactly what they changed because that noise is like the suspended wedges