One problem related to speed sensor has been reported for the 1998 Subaru Legacy. The most recently reported issues are listed below.
The speedometer on my 1999 Subaru Legacy l sedan stops working at random intervals. My mechanic tells me that this is connected to the also faulty transmission and is not just a minor speed sensor problem. Subaru denies any knowledge of these problems but I have researched and found many, many 1999 Subaru owners with the exact same problems. The 1999's had a new transmission that is very flawed and was changed again before the 2000 release because of so many problems. This is the second 1999 Subaru Legacy I have bought in the past 3 months with this very same problem (I assumed the first was a fluke and the dealer took the car back). The car has 96,000 miles and should not need a complete transmission overhaul at this point. I believe that Subaru is very aware of these faults but doesn't want to face the repercussions of a campaign or recall. I implore you to look into this. These faulty transmissions and their associated failures(speedometer, etc) are a danger to all owners. It is irresponsible of Subaru to release an entire model year that has so many expensive problems to fix.