I have a 2003 TB LTZ. I had my 3rd transmission installed about 18 months ago. The latest one has a lifetime warranty as long as I get it checked once a year which I have done. About a month ago, I went on a trip that was 200 miles one way. When I got near my destination, my car acted like it was going to die, it sort of sputtered like it was out of gas or like a spark plug was bad. I was less than a mile from my destination so I continued without any more sputtering. I checked the engine, put some gas treatment in tank (in case I got some bad gas), and couldn't find anything wrong. I went back home (200 miles), and it only did it a couple times. Now after driving it and it's getting worse, I think it might have something to do with the tranny. It sputters and feels like something is going to lock up, like bearings maybe. most of the time, it acts like it wants to shift around 45 mph or just under 2000 rpm, but can happen at any speed. It does shift smoothly when it shifts. When it sputters the tack fluctuates. I can hear a lower pitch humming sometimes . It's hard to put into words what exactly it does. I knew I needed u joints replaced so I did that. When I took the drive shaft out, the bearings were not overly greasy, in fact looked a bit dry. Not sure how much grease should be there. Replacing u joints did not fix my problem. I don't want to take it to transmission shop so they can tear my car apart and tell me I need something done for a bunch of money before they can put it back together. Any suggestions that I can check my self before taking it to the shop?