I've had a high pitched whine for about six months now and I've gone through a few different things with no success. The transmission seems fine. I did a flush and filter change and even tried some Lucas Tranny Fix in it with no difference. Put a stethoscope on it and it doesn't seem to be the source. Recently I heard that a similar whine can come from the power steering system (pump,belt,pulley...) and I'll be checking that out tomorrow. But today I had a thought. I drove in 2WD, 4H, and 4L. The whine goes away in 4L but is present in the other two. It's present in R, N, D, 3, 2, 1, but not in P. It's also dependant on RPM. No connection to speed. I read that the sound disappearing in 4L can indicate a bad transfer case. I realize this post is a little all over the place, but does anyone have any thoughts or suggestions? I'm really hoping it's not the T-case.....

 

You could try putting the truck up on jack stands or a lift and with the tires moving in gear, go around the undercarriage with your stethescope. That should make it easy to find where the noise is coming from. Just be careful if you're using stands for obvious reasons.

 

If not PLEASE take a video and Ill send you my address I could use 5k from home videos and a chance for 100K hell Id even sport for a SAS for you outa the deal!!!

 

I'll take a video just in case.....

 

di you check the fluid in the t-case? drain and replace. see what happens..

 

Got under with my wife in the driver's seat and a stethoscope in hand. Definitely the t-case. Drained and refilled with 75/90. It was a little low and whine has mostly disappeared but there's still a little something. I'm not too worried about it now. I figure that probably wear and tear from running on so little fluid for so long. Hopefully it won't crap out on me too soon. Thanks for your help guys!