Need some help with a powertrain issue on my 03 SSS!

Alright so about 2 months ago I picked up an 03 SSS AWD with 76k on it from carmax which the only reason I got it there was to replace my 5.3ecsb 2wd that got totaled. But anyways ever since I got it as soon as I go over 80mph I start to feel a bind or wabble or slipping type feeling in what feels like the front end and it gets worse the faster you go. It almost feels like somethings stickey in there, like it almost feels like the front wheels are going to fly out from under the truck. When I had my tranny guy put my shift kit and servos in I had him change all the drivetrain fluid including rear end and front diff and he said he didnt find anything out of the ordinary I didnt tell him about the feeling I was getting in the front end just because I was hoping maybe it was just low on fluid but now that I have it back its not the case. And I know its not the fact that its about to hit the speed limiter because I have a nelson tune with the limiter set at 120 or 130. Im kind of thinking the bearings in the front diff need to be replaced or maybe the wheel bearings? Im pretty sure the truck needs an alignment because the front tires are starting to round over on the outside of the tires and the backs are the same way (they were on the front right before I bought the truck) But im just looking for some help as to what it could be! I also get a slight vibration at around 57 or 58mph it feels almost like the same vibration my dads titan had when the front drive shaft went bad so Im also wondering if my front drive shaft could be an issue? And another thing ive been noticing is that sometimes when I start it the truck will jerk forward? If anyone has any ideas Id really appreciate it! P.S sorry for the long post!

You might also try posting your question here...

http://www.silveradoss.com/forums/

Ya Im a member there too but no one seemed to have an answer so I decided to try it over here too since usually everyone here always has an answer

well for one thing if your tires are unevenly worn the vibration could be coming from those. Same for the wobble, if you have a camber problem in combination with bad tires that thing will probably vibrate/pull all over the place. If you dont hear any growling its probably not a bearing, you'd hear that at 40mph. Being that you got it from carmax, doesn't it have a warranty? I know at my shop we take carmax warranties, you can probably take it anywhere.

I just got the truck back today from the dealer ship here in town where we know the guys pretty well my family brings all our cars there and I just dropped it off yesterday since I just dont have the time at the moment to diagnose it and they found a bad rear U joint so they replaced that, and then they also said they think its the tires so Im going to replace those in the next couple weeks and see how that goes! They also told me that the truck has never had an alignment with 77K on it and its not on the original tires so hopefully with some fresh tires and a good alignment it should be perfect!

if it lurches forward when you start it you have something defective in the transmission.

i had the steel belt break internally on my 95 and i felt wobble and almost like a hop, it took the rubber a little bit of time to show that something wasn't right.