I have recently noticed at highway speeds, it sounds like my driveshaft or T-case is making a decently loud humming noise. And also when I grab the driveshaft and try to turn it with my hand it has a little play in it. is this bad??? and what happens if i dont fix it soon? I drive 200 highway miles a week

 

You're going to have some play in your driveshaft because of the gears. If you have a lot of play in your DS then you have a larger issue. When was the last time that you checked your fluid levels in your driveline? Have you looked at the bearings in your rear axle? Also could it be your tires making noise?

 

How do I check my fluid levels??? And it COULD be my tires, but I really don't think it is

 

there is an access hole on the backside of the differential cover. open that and the fluid should be no less then a quarter inch below the opening. The transfer case has two spots to check it on the backside facing the rear end of the vehicle. You want the top one and will need an allen wrench to open it up... the trans you check like the engine... it has a dipstick underhood ( assuming you have an auto). You check that engine running and at temp, best after you have driven some distance. With the engine running you pull the stick out and read like the engine oil. Hope that this helps.