Whrring/Howling from front end in 4wd

Hello all,

First of all, this is on a 97 xj, 4.0, Automatic, all stock, no lift etc. NP231 transfer case (Pretty sure, no full time 4wd)

Anyway, when I am driving in 2wd, I don't get the noise, but when I am in 4wd when I get around 25-30 mph it starts making a whirring/howling noise that sounds like it is coming from the front end, possibly front passenger side, but it could be transmission/transfer case area I suppose. It is kind of a difficult noise to describe, it isn't screechy like brakes, and it isn't rhythmic like a wheel bearing. It is a real steady, somewhat high pitch, almost like a tea kettle whistling, but not real loud. It is quite noticeable with the radio off, but with it about half volume you can't really hear it.

It only happens in 4wd, if I shift to 2wd, it stops immediately, and it only happens when I am on the gas. If I let off it goes away pretty much immediately as well.

Where do I even start looking? also, should it be alright to drive in 2wd for the time being as it doesn't make the noise then? I have only been putting it in 4wd when absolutely necessary and then switching out when traction improves.

Does it get worse with more speed? My first thought goes directly to the front driveshaft since you say its only there while applying gas putting it under load or something. Perhaps check if its properly greased.

I'm sure there are some more knowledgeable people to chime in.

Thats just my .02

I had the same problem a couple years back. I was getting ready to tear my transfer case apart and removed the driveshaft. When I did I noticed the double cardon joint didnt move, turned out it was a seized u-joint. Its worth pulling the front driveshaft and checking the joints.

So it sounds like I'm going to pop off the front drive shaft tonight, should I be checking for loose joints or joints that don't move smoothly?

My problem was one that didnt move, though it could be either. I would think a loose one would be more of a clunking, but U-joints can be very hard to diagnose.

while your driveshaft is out, try to wiggle the front pinion. If it moves at all by hand either left to right or up and down, it is likely you have some pinion bearing problems. That tends to happen with the LP D30 and any amount of lift on an XJ

x-jay vision said:

while your driveshaft is out, try to wiggle the front pinion. If it moves at all by hand either left to right or up and down, it is likely you have some pinion bearing problems.

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True

x-jay vision said:

That tends to happen with the LP D30 and any amount of lift on an XJ

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A true statement but inapplicable in this case. The OP has a 1997 which should have a HP (high pinion) D30. Jeep put the LP (low pinion) D30s in the 2000-2001 model years.

A true statement but inapplicable in this case. The OP has a 1997 which should have a HP (high pinion) D30. Jeep put the LP (low pinion) D30s in the 2000-2001 model years.

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This is true. I realized about 3 seconds after posting the OP had a 97, I was hoping noone would catch my mistake. I should have known. Good catch HappyDog

is the noise the same in 4HI and 4LO ? you didnt specify. 4LO will give a bit of gear whine from the transfer case.
otherwise i'm thinking front shaft issues.

sidriptide said:

is the noise the same in 4HI and 4LO ? you didnt specify. 4LO will give a bit of gear whine from the transfer case.
otherwise i'm thinking front shaft issues.

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Haven't checked 4 lo yet, but I would assume the noise wouldn't be there as it doesn't happen at low speed, only once I get to about 20-30 mph.