1997 Subaru Outback Tranny not shifting

My car starts and runs in drive, reverse , and even low 1 & 2, but it won't shift. I can only drive about 15 to 20 mph. I changed the fluid and replaced the filter. The filter was clean. My speedometer stopped working when the transmission stopped working. Could this be as simple as the vehicle speed sensor? Or what else could it be?
Thanks guys your site is very informative.
John