Transmission replacement?

I am not trying to insult anyone with the donation that I am offering but all I have is that amount and this is my only car. A year ago we replaced the cvc joints first, because it acted like the cvc joints were going out, clicking when it turns either way, car drove smooth for awhile, then fifth gear went out, sheared down to nothing, with no grinding or any other noise, we replaced just the fifth gear, car ran smooth the first time we drove it, then the second time we took it out fourth gear went out, we drove it until we could replace the transmission, when we did we got a used transmissiona but we checked it out and everything was fine, put it in and car drove smooth for a few weeks, then the wobble and shake in the front end started again, drove it like that for a few months, and just the other day was driving to go out of town and was in the fifth gear when fifth gear went out again, with no noise at all just sounded like I was running in neutral, took off the outside plate on the transmission and fifth gear was sheared to nothing again What is the prolem, what can we do to fix it