diff --git a/src/main/java/com/github/stephengold/joltjni/VehicleTransmissionSettings.java b/src/main/java/com/github/stephengold/joltjni/VehicleTransmissionSettings.java
index d8779c0..0e29d3a 100644
--- a/src/main/java/com/github/stephengold/joltjni/VehicleTransmissionSettings.java
+++ b/src/main/java/com/github/stephengold/joltjni/VehicleTransmissionSettings.java
@@ -30,14 +30,6 @@ of this software and associated documentation files (the "Software"), to deal
  * @author Stephen Gold sgold@sonic.net
  */
 public class VehicleTransmissionSettings extends JoltPhysicsObject {
-    // *************************************************************************
-    // fields
-
-    /**
-     * prevent premature garbage collection of the underlying
-     * {@code WheeledVehicleControllerSettings}
-     */
-    final private WheeledVehicleControllerSettings vehicle;
     // *************************************************************************
     // constructors
 
@@ -45,14 +37,13 @@ public class VehicleTransmissionSettings extends JoltPhysicsObject {
      * Instantiate a settings with the specified native object assigned but not
      * owned.
      *
-     * @param vehicle the underlying {@code WheeledVehicleControllerSettings}
+     * @param vehicle the containing object, or {@code null} if none
      * @param settingsVa the virtual address of the native object to assign (not
      * zero)
      */
     VehicleTransmissionSettings(
             WheeledVehicleControllerSettings vehicle, long settingsVa) {
-        this.vehicle = vehicle;
-        setVirtualAddress(settingsVa, null);
+        super(vehicle, settingsVa);
     }
     // *************************************************************************
     // new methods exposed