noobie question/front end hummm

First i'd like to say nice forum you got here. ok now for my situation.

my wife and I bought a 99 cherokee sport about a year and a half ago(68k). The thing has been great untill recently. just last month I had the local oil change place change the front, rear, and transfer case fluids. They were gray in color at 80k. So I figured that it was really needed to be changed. now I get a humm from the front end. Doesn't matter if it's in 2wd or 4wd. the noise starts at 30mph. Here is the list of things that I am thinking of checking.

1. Tire pressure, worn tires
2. cv-joints
3. U-joints
4. hubs?
5. bearings?

I know that this is something that has been asked alot. but I just thought that maybe someone could give me some insite as to the common problems with these jeeps. This cherokee is not lifted. It is all stock. I have no idea if the tires were properly rotated. They don't look to old though.thanks in advance for the help.

If you had all of your oil's changed and a new noise appeared. I would check to make sure that new oil was put back in and it was the right type. Check the front differential and see if it is full. You need GL5 oil for this. The transfer case uses Dextron III automatic transmission oil, it should be red.

See if you can narrow down the hum a little. Does it change when you let off the gas, or coast in neutral? Does it change with engine speed rather than road speed? How about when you turn the steering wheel? The more you can detect of how that noise occurs and when, the easier it is to diagnose.

If it is entirely speed related, but seems to vary a little on curves, suspect a wheel bearing (hub unit). Usually these bearings will go dry, wear out, and make scraping noise and you can feel the play, but sometimes one will become pitted, and there will be no play, just a humming noise which can be a little hard to trace. You may have to jack up a wheel and spin it, and even then, you'll have to be very attentive, because the axle shafts and brakes make it hard to give the front wheels a good spin.

Other things to do:

Crawl under the car and wiggle things. Look at both driveshafts and their u-joints. Don't count on your perception of where the noise comes from, because sometimes sounds will telegraph in odd ways.

Any odd tire wear should be a tipoff. Try temporarily rotating front to back, and see if the sound changes.

As noted above, check the fluids.

It does it while coasting and while on the gas. I haven't tried neutral yet. not sure if the noise is there while turning. I plan on jacking it up soon or crawling under it to see if anything has play. and I will rotate the tires too. I just thought that I'd discuss this with someone before I get under the thing. Go figure that I don't drive this thing that much (wifes car) and when I do it makes a noise.

Well I climbed under the car and pulled on some things. The front driveshaft was tight. the control arms also tight. I didn't get to jack it up, but I did pull on the u-joints (cv-joint) not sure of the correct name. And the passenger one had more play than the drivers. It is right by the wheel. I think it's called the hub.

It's the hub, I gave up and took it to a shop. they pulled off the passenger side and it was almost sized. they showed me the part and it would barely turn!!! Hopefully they don't have to do the same for the other side.

Not to scare you, but read the recent thread titled "Transfer Case Exploded!!" That event on a 2000 XJ was also forewarned by a front end hum.

Sand-Dog said:

Not to scare you, but read the recent thread titled "Transfer Case Exploded!!" That event on a 2000 XJ was also forewarned by a front end hum.

Click to expand...

Thanks for the heads up. I will take a look at it, but so far it's doing great with the passenger side Hub/bearing assembly replaced. So that was a $340 buck fix.