Two problems related to rear suspension have been reported for the 2004 Subaru Impreza Wrx. The most recently reported issues are listed below.
Rear struts bind and seize due to inadequate lubrication. First two occurrences at ~15000mi, third occurrence at ~30000mi, fourth occurrence at 40000mi. Dealer has replaced both originals and one of the replacements under mfgr. Warranty for same problem. Problem has nonetheless recurred again- total defective parts now four. Warranty now expired and dealer will not cover part in good faith. Internet resources make this defect appear to be quite common amongst owners, but Subaru has not acknowledged how frequently this occurs.
Rear suspension struts bind and clunk due to lubrication issue. Both original struts replaced under warranty as well as one of the replacements and problem has returned again for a total of 5 failed struts. Warranty has now expired and repair would be at my cost. The binding has progressed unabated and will likely result in time in complete failure (frozen or unrestricted movement).