Suspention

why car bounces in back

Too much junk in the trunk?

Probably shocks/struts.

A car bounces in the back because it has springs on the rear axle.

Likely you need new shocks or struts back there.

Make model year and miles would help.

The purpose of shocks or struts is to control the bounce from the springs. If it bounces, the shocks or struts are shot and need replacement.

can both shocks in the rear go at the same time or can it have anything to do with the switch it has a 3 way variable switch for shocks(SOFT ,MED ,HARD) it is a 1995 montero 4wd sr

Yes

You are SO lucky. The Montero has shocks rather than struts. That’s lots easier to replace. Lots cheaper if you’re having it done.

Yeah, you need shocks.