At random, seems to be after about a half hour or more of driving, when I'm slowing down startin at about 25 mph there's like an electronic humming/whine type of noise coming from somwhere under the jeep, seems to be coming from the middle like where the t-case is. Doesn't matter if I hit the gas or let on or of the brakes the noise doesn't go away. When i come to a complete stop the noise stops an when i accelerate from a stop the noise isn't there. I crawled under the jeep after driving it with that noise and the front axle diff doesn't feel hot but the bottom middle of the t-case feels pretty hot. This only started happening after I pulled another jeep out while I was in 4 Low. I'm pretty sure I have an NP231 transfer case (2, 4 part time, 4hi, N, an 4 low) the transfer case has 158,000 miles on it and I drained and changed the fluid with the correct fluid at I think like 133,000 miles can't remember exact number. So should I start lookin for a new t-case or try to rebuild mine? Or just check fluid level an drain an refill it? The only issue there is the fill plug is bein a pain in the *** to get out don't know why they used a hex key style plug instead if a bolt you could get a socket on

 

The transfer cases do make noise, it might have always been making this noise but your just now noticing it.

 

No it's pretty loud, I never noticed even the slightest noise before, if I was driving around in 4lo it might make sense but this is happenin In 2wd. Everything feels fine though no noticeable changes

 

My bad, just saw transfer case. Haha I'd lean away from it being a tcase problem. Check your ujoints. Grab your driveshaft and twist it. It should spin a little but you'll notice if it has significant play in it. It could be as simple as a ujoint going out.

 

Haha it's all good, but ya I checked all of them that was my initial though but I just redid all the front axle u joint tie rods ball joints etc, I checked the front drive shaft joints an they feel fine. The reason I'm thinkin t case is cause the whine/humm sounds electronic

 

I gotcha, have you checked the fluid? If it's low, it will cause a noise all the time. As it is always moving.