Hubs or T-case?

[flyhigh5574]

I have had noises (grinding and buzzing) coming from the t-case on my 91. I lifted the vehicle and tested all three 2hi, 4hi, 4lo and I could definetely hear a popping and grinding noise coming from the t-case. When I put it in 4hi when the vehicle was off the ground, the wheels were locked so I gave a little more gas and then POP and all four were turning. Same thing happend when driving. It seems like the front was locking up. I would also have a buzzing noise at low speeds in 2hi (5-15 mph) that would dissapear once I pushed the 4hi pushbutton. I am pretty sure that the electric shift motor works fine as I have no problem shifting into all three gears. To try and isolate the problem, i removed the front driveshaft between the t-case and the front diff to. I lifted the vehicle up, put it in drive and the noises were gone. I tried 2hi, 4hi and 4lo and no noise. The t-case was turning fine. My guess then was that there was possible a problem with the auto hubs or possibly the front diff. I took it for a drive without the front driveshaft installed and everything sounded great in 2hi. I went to a parking lot, stopped the vehicle and put it into 4hi. Started to move and instantly the noise was back. I took it out of 4hi and the noise was gone. Tried the same thing in 4lo and got the same noise. Keep in mind this is without the front driveshaft. My question is, first, what could be the problem? And second, is it possible for the front hubs to engage without any torque coming from the t-case? I always thought that there had to be power coming from the t-case to the front diff for the hubs to engage. Is it possible that the hubs are engaging by themselves? Could this possibly explain the buzzing noise that I would hear that would dissapear once I shifted from 2hi to 4hi? And finally, could bad hubs somehow make the t-case put out an awful noise? One last piece of information. There was a few times when the buzzing noise would turn into a thumping noise that would lead to the vehicle locking up and then begin rolling again. This is why I initially suspected the t-case. I know that the hubs contain plastic parts and I didn't think that binding plastic pieces could make the vehicle act as it did. Thanks

 

[MrShorty]

By removing the front driveshaft, you have completely isolated the transfer case from the hubs. What I mean is, the hubs now have no way of knowing what position the t-case is in, so they should behave the same in 2H, 4H, and 4L (and should stay disengaged). The fact that the noise is goes away in 2H suggests to me that the problem is in the t-case.
Have you checked t-case fluid level and condition? Someone hasn't put gear lube in your t-case (supposed to be ATF)?

 

[flyhigh5574]

Seems like there was too much fluid in the t-case. When I opened the check plug fluid came gushing out. To the best of my knowledge, fluid should be up to the check plug right? Anyway, I have figured out that the problem is the t-case. The noises are definitely coming from the t-case. Also, by taking a closer look at it I noticed two decent size cracks in the housing. I guess there goes the possibility of a rebuild! I've got a replacement on the way and I will soon take apart the old one to see what happened. Thanks for the help!