One problem related to gasoline engine has been reported for the 1999 GEO Tracker. The most recently reported issues are listed below.
Current unrepaired condition. Vibration,engine and or related components between speeds of 35mph and 40mph also at speeds between 55mph and 60 mph severe enough at times to make entire body of vehicle vibrate, have driven other like vehicles some exhibit this condition, problem seems to depend on local speed limits and driveing conditions. I have found a similar report in your database concerning the Suzuki grand vatari which is manufactured along with the Geo Tracker at the cami automotive plant in canada. Chevrolet acnowledges this condition as normal. I suspect the problem to be improper engine to body isolation.