question about transmission

[demonsvx]

I have a question about my transmission. Last fall my tranny started to act up and I decided to park it until spring. Heres what it is doing when I first start it up it goes into all gears but after about 2-3 minutes no movement in any gear and I car hear a slight sucking noise. What could this be a clogged filter or a more serious problem. I changed the fluid but could not change the filter in the pan due to a hard line that goes over it. I could not remove this line or get the filter out What is this line for and could a clogged external filter cause this problem. By the way my SVX is a 1992 LSL with about 112000 miles: Thanks for any help you might have. Damian