Clicking and Vibration

I have a 97' GMC sonoma extended cab. It's a 2.2L 4 cylinder 2wd manual. It has 63K on it. I replaced the transmission at 55K due to a bad blocking ring for my 5th gear. The truck ran great for about 6K no problems. About 2 thousand miles ago a heavy vibration started when driving in the snow one day. Only at speeds excess of 25mph. A little after the vibrations started I started hearing a clicking noise fromt the rear when I accellerated. The clicking gets faster as I go down the road and slower as I slow. At first the noise only sounded when accelerating from a dead stop, under load. Now it sounds in almost all gears under heavy load, and sometimes when I'm just cruising along. Every now and then the sound is met with a loud clunk from the rear that can be felt all the way through my shifter. The only other way I can describe this sound is the "clank" sounds like a hammer smacking metal. And the "clicking" sounds the same. Just at a much lower volume that eventually speeds up into a screeching noise. It's definatley coming from the rear of my truck and the vibrations are tremendous. Please help.