The pump only provides the pressure to raise and lower the vehicle, the spheres provide most of the shock capability. The pump has nothing to do with the shock capability. With the car turned off the suspension still functions but will not self level.

The shocks themselves are mainly the ride height adjustment platform and work with the spheres to provide the shock capability.

If the car has been used with the spheres badly worn then the shocks can be damaged which will lead to the condition you describe, shocks however rarely go bad and it's only when they are used with the damaged spheres that they get destroyed.

My suggestion would be to try shocks from a dismantling yard first to ensure that this will fix the problem as new SLS shocks are very expensive.

You should get the tandam pump repaired anyway as running it low on fluid will damage the pump.

Good luck.

Matt.