So I am getting a bad vibration when accelerating. Prior to this there was an occasion bang like gears slamming or metal hitting when beginning to drive. From what I read I'm thinking it's the 1st joint on the cv axle. My front driverside cv is covered in grease and oil and has been since I bought it 3 years ago so I'm assuming that is the culprit. However I just realized that when driving in 2wd(always) that it should be the rear wheels engaging and would have to be a rear cv? I am at work and the tahoe is at home so I can't even investigate it until later tonight. My issue is I ordered a FL CV axle yesterday and we are very short on funds so now I'm debating canceling the order hopefully before it goes out or maybe being able to change the order? Any help would be great. Is the tahoe possibly FWD when it 2wd? Could the selector be malfunctioning and its actually in 4wd all the time?