Suspension problem???

I have a 2002 p38 with coil spring and rubber spacers on the springs to accommodate a slily bigger tire (it's been like that for over a year and I use it off road from time to time). Recently I feel a hit under the body at the rear maybe middle of the car behind he driver seat or left rear wheel when I hit a hole or over a speed hump (it feels like a hit with a rubber hammer). I jacked the vehicle by the diff and try to move the suspension components but nothing seems to be loose and the rubber of the arms and bar are OK, the shocks are bilstein and are almost 2 years old. I can't hear any noise from the suspension but I can feel the hit. Also try to feel it by rocking the car from side to side and up and down and could not feel anything. I'll jack it again on Saturday to put jack stands on the chassis so the suspension hangs in the air to verify everything again and maybe hit the tire to see what happens.

Any ideas? Could it be the rubber on the sealed part of the arm?

The banging underneath on mine was the heat shielding, the retaining clips had rusted away allowing the lump to swing on it's front mountings and bash the floor under the drivers seat.

Thanks, hopefully I have the same problem.

I remove the coil springs and shocks, took a look at the arm bushings and everything is fine. The thing is driving me crazy. Could it be something in the front, even when the noise happen when I drive the rear wheel over the speed reduction?

often shocks