Applied Luis Arias' commit 9b43c3ba7f10864566f8 and added a unit test.

Author: pledbrook

src/java/org/codehaus/groovy/grails/web/metaclass/ChainMethod.groovy

@@ -57,11 +57,15 @@ class ChainMethod {
 
         UrlMappingsHolder mappings = appCtx.getBean(UrlMappingsHolder.BEAN_ID)
 
+        // Make sure that if an ID was given, it is used to evaluate
+        // the reverse URL mapping.
+        if (id) params.id = id
+
         UrlCreator creator = mappings.getReverseMapping(controller, action, params)
         def response = webRequest.getCurrentResponse()
 
         def url = response.encodeRedirectURL(creator.createURL(controller,action, params, 'utf-8'))
         response.sendRedirect url
 
     }
-}
+}

src/test/org/codehaus/groovy/grails/web/metaclass/ChainMethodTests.groovy

@@ -25,6 +25,10 @@ class TestChainController {
             chain(action:'create',model:[book:book])
         }
     }
+
+    def testId = {
+        chain action: 'show', id: 5, model: [str: "Test param"]
+    }
 }
 class TestChainBook {
     Long id
@@ -55,5 +59,11 @@ class TestChainBook {
         println flash
     }
 
+    void testChainMethodWithId() {
+        def controller = ga.getControllerClass("TestChainController").newInstance()
+        controller.testId()
 
-}
+        assertEquals "Test param", controller.flash.chainModel.str 
+        assertEquals "/testChain/show/5", response.redirectedUrl 
+    }
+}