Firstly thanks for taking the time to read this, I have searched high and low and cannot find anything that seems entirely relevant to my particular problem and am looking for some insight on testing I can do to find the culprit. I have a 2003 Montero Sport XLS, which is AWD, that is grinding like the transfer case isn't engaging but from what I can tell the 4WD seems to work (I can tell when trying to make a sharp turn in 4WD). The grinding occurs when in AWD, 4H and 4L. I have searched high and low for the vacuum under the hood that I keep seeing being referenced but I'm pretty sure that is not on my model. I've tried to shift between AWD and 4H and 4L a million times and still nothing. I can;t remember the last time the 4H/L indicator light came on but just chalked it up to a burnt bulb as the 4WD seems to be working. Any help would be greatly appreciated.

 

*update*

The 4H light is working now but the sound remains. I'm not sure grinding is a good descriptor it sounds like really loud rattling like a gear is shaved or a chain is slipping (assuming there is a chain in there). Can I jack the truck on all four and determine anything that way?

 

This is a bit puzzling. When I first read your post I was leaning towards a bad 4WD solenoid, but that doesn't explain why you'd be having this issue when AWD or 4WD is engaged (it would only happen in 2WD).

Does the sound occur when you are engaging the 4WD or only when its engaged and you are driving? Is the sound constant? Does the sound frequency change with speed increase?
is it worse (or does it go away) when you turn?

Start by checking oil quality and level in the transfer case and in the front differential. If you see metal shavings there - you may have a problem. If oil is clean and not low, then the problem might be in some other place. Try to observe more under which conditions the sound occurs.

 

The sound is constant as long as the truck is driving. It seems as though it is more pronounced when there is a load on the truck. It is definitely something drive related as it gets louder relative to speed. If I am easy on the gas it will not start making the noise until around 10 MPH or so. The sound is less prominent when turning but still present.

I will be checking the oil levels/quality tomorrow. Thanks for the reply.

 

Are you able at all to narrow down where the sound is coming from - Front, Back, Right, Left, etc? You said the sound gets louder with speed, what about frequency? Does it change?

 

I have a grinding sound that I have been experiencing recently on my 2003 Montero Limited. If I engaged the 4 wheel drive then the sound stopped. I thought I had a piece of the wheel well liner come loose and that it was rubbing on the tire. I found no wear on the loose piece of the wheel well. During further inspection I noticed some metal shavings on the inside of my left rim. I pulled the wheel and checked the brakes, and they were fine. I found some grease on the back side of the dust plate. It Turns out that the noise was coming from my left front CV Axle. I am trying to replace that right now and I need help to figure out how to remove the CV Axle... Stuck trying to get the dust cap off at the moment. Help Please !