i have an auto tranny, and a few weeks ago when I put it in reverse the gears wouldn't engage. the engine would rev, but it wouldn't move anywhere. the next day it started to work again, but after about 2 weeks, when I would go from drive to reverse it would make a really loud clunk sound and it felt like the tranny was going to fall out. After that happened a few times it wouldn't move in reverse again. So today I fired her up to see if maybe it was engaging the reverse gear, it wouldn't, but when it's in Park or Reverse and I rev it, it makes this whining sound, but it doesn't do it in neutral. After i revved it a few times, it would make that same whine at idle in both park and reverse. Is there anything i can check to figure out what might be the problem before i take it to a shop to get it inspected?