Rear Differencial, Transmission, Etc.

I have had multiple rear differencial problems with my '03 CTS. At about 15K miles, I also began to hear the whining, so I took it into the dealership & after almost 2 weeks they said they were going to replace the rear differencial. 3 days after I picked the car up, I was brought to a screaching stop at 35 mph. There was a loud bang & then I had no control of the car and was stopped in seconds leaving most of the tread of my tires on the road. They towed the car in & said the diffenencial fluid had leaked & blew the part. They replaced the part again & had someone in service department drive it & it started slipping again, so they decided to replace the entire rear axel & differencial. At this point I did not want to take the car back, but they assured me it would be okay & I was out of lemon law because I had the car over a year. Well, when I took it to have the oil changed last week, and while it was on the lift we noticed the differencial was leaking again, so it is in the shop again. It now has 25K miles and I am 100% positive that if we hadn't had the oil changed when we did, the fluid would have leaked again bringing me to another screaching stop & I live in the mountains, so they are lucky I was okay the first time. They called 2 days ago to say they didn't think the car could be fixed since it would be the 3rd time, but said they had to speak with GM first to see what the next step was & would call me back. They called today to say they have a new way of fixing the differencial by draining it and using a different sealant & leaving it to sit empty for 2 days to completely dry. I am still trying to work with the Cust. Service department to try to get a buy back. We'll see how that goes. As if this shouldn't be enough, I have also been brought to a complete stop while on the same road as before going 35 mph when my CPU told my fuel pump to shut off, this was in December so when it went into the shop, they replaced the entire computer chip. Oh, I also forgot the fact that they are also replacing the transmission while it's in the shop this week b/c it's leaking & making noises. These are really just the major problems not including the front seat always breaking, license plate area leaking, and the list goes on. I love the vehicles looks, but no longer feel safe in the car. If you have signs of the diffencial having any problems, I urge you not to drive the car b/c the results of it breaking could be devistating. I am beginning to think that's what it's going to take for GM to buy the car back. I hope no one else is having as many problems as I am, but if you are, please contact me.