When the transmission shifts at high rpms it feels like its going to come up throuht the floor board of the car. And how can you tell if the ujoints are going out or not?

 

I had the exact same problem. It turns out that the only thing wrong was that the transmission mount was bad. I'll bet that if you pull your transmission mount off it'll be torn.

 

is replacing the mount something i could do on my own and not have to drop the transmission own or something? and how do you do it?

 

It's a really easy thing to do. I'm not very good with working on cars and I did it no problem. Go buy a replacement mount from your local parts dealer. It'll cost you anywhere from $20-$30. Look under your car and you will see a crossmember running from the passenger side to the drivers side close to where the driveshaft connects to the transmission. Its held in place by 4 screws, 2 on each side. Place a jack (its a good idea to put a small piece of 2x4 on top of the jack so that it will support the transmission better) under the transmission right behind the crossmember and jack it up just until you have some supporting pressure on the transmission. Remove the nut in the center of the crossmember (this is what bolts the crossmember to the transmission mount). If the bolt only spins and wont losen up, no big deal, you can just remove it after this next step because it probably means your mount is ripped in half like mine was. Remove the 2 bolts on each side of the crossmember. Next you will need to remove the 2 bolts that hold the mount onto the transmission itself. At this point you should have everything removed that needs to be. Bolt your new transmission mount back in place in the reverse order. Your new transmission mount is now installed and no more bang under the floor.