Hears my long story about 2 years ago my tranny blew so I purchased a jdm transmission off one of those ### engine & tranny shops

. They told me it would work on my car and that that it was off an eagle talon, but I doubt it. I had no other choice at the moment so I purchased and had it installed.
My car ran ok for some time but after getting on the highway (100-120 km/h) in 5th gear on a rainy day it seemed like the rear was trying slip to one side and it was even worse in the snow. It's ok on a dry day but I've been avoiding the highway just to be safe.
While logging full 3rd-4th gear pulls on my Dsmlink my car hooks up fine it only does this when cruising in 5th at highway speeds.
After doing a search a while back I came across a couple of threads that mentioned how some jdm trans have the wrong final drives and that it causes the front and rear wheels to move at different speeds, so I'm pretty that's what I have. I haven't done anything since then which was over a year ago.
I recently met another guy in my area with the same problem so I did a little more searching on several forums but came up with nothing again.
My question is can someone tell me if there's some way to change the rear diff to match the jdm trans? I'm not sure what I have yet, might be an evo 1-2 trans. Anyone have any trans identification info I can use to figure out what I have? Any help will be appreciated.