Jeep Cherokee rear axle whine

[jeepman3071]

I have a 2000 Jeep Cherokee 4.0L, automatic with the Dana 35 rear axle. The jeep has about 113k on it and ever since I bought it at 80k I have heard this rear end noise. The noise is more like a "howl" or whine and only occurs at speeds of 48-52 mph. Doesn't matter if I'm gently accelerating or coasting. On the highway I can't hear it or around town, only on mainly 50 mph roads. Any idea what this is? How costly/time consuming to fix? I'm thinking its a pinion bearing. The noise hasn't changed much if at all from when I first bought it. I have regularly changed the differential fluid.

 

[Hokiefyd]

Noise like that is usually a bearing or a lash problem. I don't know if this noise is common on Jeeps, but this noise was very common in the Dakotas with the Chrysler 8.25" rear axle (standard axle). Many of them did it since new, and warranty axles would make the same noise. Just seems to be the way they were, and didn't impact longevity. Since yours has done it since you bought it, I'd say it's probably done it since new as well. My family had a few Cherokees, and I seem to remember the rear axles having some noise to them.

 

[saberz]

Sometimes it could be the gear oil as well. Xterra members (1st gen) stated that 80w90 is preferred as if you use 75w90 you would experience that. Matter of fact I did experience it when I did the switch, had 44k on the SUV then. But it could also be something else, sure it isn't tranny whine?

 

[mechtech2]

Any bearing wear [pinion or carrier] will change the pinion/ring gear angles. Noise is directly and indirectly attributable to the bearing. Who knows what is faulty in yours? Sometimes a simply fresh fluid change, or a thicker fluid will attenuate noise like this quite a bit.

 

[meep]

simple things first--- when did you last rotate tires? M

 

[jeepman3071]

I last rotated my tires about 2,000 miles ago. They are almost new and are wearing great. I rotate them every 5k. As for the noise I understand it is common in jeeps. My previous Cherokee had the 8.25 chrysler axle and had a loud whine only when coasting which I was told was gear lash. I just find it odd that this noise is constant depending on the speed, not necessarily load. I am running 75w90 Mobil 1 synthetic gear oil, and it made the noise before with 75w140. I'll try changing the fluid back to a thicker weight and see if that helps. Like I said before the noise hasn't changed much, I just want to make sure its not something that will grenade the axle in a month.

 

[440Magnum]

I've never had a noise problem with an 8.25, and I've owned quite a few. I have had noisy Chrysler 9.25s. But then neither is relevant since this is a Dana 35 Jeep anyway. The Dana 35 gets a pretty bad rap on the Jeep forums compared to the 8.25 it seems. Since its load-independent, I'd suspect that its either just the way the ring/pinion mesh is set-up on that unit, or else its a wheel (axle) bearing issue. Pinion bearings are loaded VERY differently under acceleration vs. coasting, so they tend to sound very different when coasting or accelerating if they're the problem.

 

[jeepman3071]

Originally Posted By: 440Magnum

I've never had a noise problem with an 8.25, and I've owned quite a few. I have had noisy Chrysler 9.25s. But then neither is relevant since this is a Dana 35 Jeep anyway. The Dana 35 gets a pretty bad rap on the Jeep forums compared to the 8.25 it seems. Since its load-independent, I'd suspect that its either just the way the ring/pinion mesh is set-up on that unit, or else its a wheel (axle) bearing issue. Pinion bearings are loaded VERY differently under acceleration vs. coasting, so they tend to sound very different when coasting or accelerating if they're the problem.

That is true. Thanks for the input. I know the Dana 35 has a bad rep, but mostly because it is weaker and breaks shafts more often under the stress of larger tires. However, I've seen many stock ones go over 200k miles. I guess I will just change the fluid to something a bit thicker and run it till it blows.