Air if I remember correctly.
I believe that the rear air shocks are part of an automatic level control system. There is a level sensor on the rear suspension system and a compressor that fills the shocks to raise the rear end. There is also a valve to release the pressure to lower the rear end.
Rear air shocks work by using a small air compressor to provide additional lift and support. This is particularly handy for towing heavy loads.
The 2001 Buick LeSabre rear shocks are held in place with a retaining bolt on each end of the shock. Remove the retaining bolts and the old shocks will come off. Reverse the process to install your new rear shocks.
Struts in the front and air shocks in the rear.
They have air shocks in the back that are used for ride height control. This is not the same as an "air spring" system. They have regular rear springs and the air bladders in the shock are only pumped up when there is significant load in the rear, to prevent the rear end from sagging. This is a very simple and reliable system. Monroe makes great factory replacement rear air shocks and they are cheap too.
You can find a good tutorial at http://airsuspensionreviews.com
Lesabres only have air suspension in the rear, they will be a combination of air shocks with a coil spring on the lower control arm.
Yes they can.
the rear shocks on the newer Envoys are air shocks, and wear just like the other ones, however there is also a compressor in the system that is prone to failure.
Replace the shocks, or struts if equipped.
As of 2014, there are a few places where one can get rear shocks for a 1994 Chrysler New Yorker with air ride. This can be purchased at Auto Zone and O'Reilly's.