Hello, I just bought a 2000 Subaru and am having issues with the transmission. After about a week and a half driving it the car started to pop and jump when I was starting up forward and reverse. I took it to a mechanic that the place I bought it from recommended and he said that the transmission was bad, since I had a warranty it only cost me $341 to fix. The transmission he put in has a low humming noise when I am moving. It also has a low grinding sound when I shift from 1st-2nd and 2nd-3rd. The stick is also VERY sloppy when it's in gear. He seemed to have trouble finding a transmission that would fit. The first one he got had a cracked housing so he needed to get another one. He said he put in some oil that might quiet it, I doubt it is going to change anything. He said to call back Wednesday if it doesn't go away and he'll have to find me another transmission. I'm trying to be proactive and find out what transmissions would work for it because I really love the car and am a big fan of Subaru. I searched Jasper for my car and put in the VIN, the search came up saying it was a manufacturer’s model TY754 transmission, and also that they are out of stock

Here are my questions, thanks in advance for your answers:

1- How can I be sure what transmission I have?
2- How can I determine what year/model Subarus use my same transmission in order for a quick swap?
3- Is there an easy fix for this problem?
4- Why is my mechanic having such a problem finding a good transmission and why won't the warranty cover a rebuilt transmission? (I understand answers to this question are most likely to be just your opinion, but I'd like it anyway.)

Thanks again!