I have a 1998 Blazer 4x4. I get a whining / grinding at 30+mph. The pitch gets higher the faster i go and it does not change when my trans shifts. When i'm on the freeway and turn left it completely goes away. I've noticed a few very small spots in the driveway over the last couple of days. Also i see what appears to be trans fluid accumulating and dripping from the outer rear corner of the fuel tank. Does this sound like the output shaft seal or the transfer case? The left turn thing is throwing me. Please help.

 

im taking a large assumption that the simple stuff has been checked first,
Brakes, rotors, front wheel bearing etc, all the simple things, is the noise comming from the front or rear..

 

It has the symptoms of a bad front wheel bearing. Usually, not always, whatever direction you turn to make the noise less noticeable, or go away, is the side with the bad bearing. In your case, the left bearing. Each hub assembly, (left & right) has two sets of ball bearings, side by side: When you turn left, the outer left and inner right set of bearings are unloaded, and the inner left and outer right are loaded. Turning to the right causes the opposite to happen. Keep in mind that sound travels through the vehicle, and it can be difficult to pinpoint which side the noise is actually coming from. If you raise the wheels off the ground, and grab the tire at 3:00 and 9:00 positions and push/pull, you might be able to feel looseness, that would be the bad one A more accurate way of locating the bad one is using a stethoscope on the hub while the wheel is rotating.

 

Just had the front driver wheel bearing replaced 2 weeks ago. Breaks, uppers & lowers, inners & outters were all good. And i thought the noise was coming from the front, but at this point i'm not really too certain. Should i assume that a bad transfer case or output shaft seal wouldn't cause what i am experiencing?

 

Nothing in the transfer case is affected by turning the steering wheel.

If the left bearing replacement did not affect the noise, it's possible the inner bearing set on the passenger side is causing the problem, (it is unloaded on left turn).