98 GC I-4 - High Pitched Whine @ Freeway Speeds

[yeller]

Status:
- 98 Grand Cherokee Lardeo
- Inline 4
- 47K Miles

Problem:
While driving at freeway speeds at ~45 to ~65mph I hear a high pitched whine. If I remove my foot from the gas petal the whine immediatey dissapears. There is no whine at lower speeds and comes around at approcimately ~45 mph, sometimes not till around 65mph (it's not consistant at the exact same speed). It's loud enought to be annoying.

I am unable to determine if the whine is coming from the front or rear of the Jeep. Any suggestions would be greatly appreciated.

[yeller]

One more update. The whine has been evident for the past few years and replacing the air filter doesn't work.

[JDPascal]

welcome to AF


possible causes for your noise are:

universal joints
carrier bearings
inner pinion bearings
transfer case bearings

I would check them in that order.

Remove the drive shafts to check the u-joints. They should be free moving and no signs of rust around the cap seals for the parts you can't take apart easily.

To initially check the diffs and transfer case, drain the oil from each into a separate, clean container. An ice cream pail works good for this. Look for any silver in the oil - thats likely bearing material..... You can also use a magnet to run thru the oil and see what gets picked up. If you have time, let the oil sit for a while and see what settles out to the bottom of the pail.

If you discover a silver mine, in the diffs, the axles will need to come out to remove the carrier/pinion and depending on what else you find you may want to just rebearing the whole assembley.

Rear axle bearings may also cause a noise but it is unlikely to change as the load moves from drive to coast like you describe. Same with tire noise.....

Even though your mileage is so low, it's likely a good thing to change the oil in the diffs and t-case considering the age of the unit.

Hope this helps......

JD