Hi Folks, I have a grinding from the front of my Jeep. It gets louder with speed but it also varies with whether or not I'm hitting the gas. I've wobbled the wheels and there is no movement so I'm guessing the bearings are OK. I thought it might be the driveshaft UJ's but I get a lot of noise if I'm doing a really hard turn with the steering fully turned, the wheels judder also and the car moves very jerkily. This is making me think it is the front diff. I haven't checked the diff oil level yet because the inspection plug has seized. I might have to pull the cover anyway so are there any other things I should be checking to see if I have a problem with the diff? Repair manual is useless, it just says take it to the dealership. Any ideas or advice much appreciated. It's a 97 with 150k miles on it. Cheers, Stuart

some hopping in 4wd on solid surfaces is necesary.  For the noise to change when you are on the gas in 2wd would have no connection to the front axle.

Guess I am just looking or more clarification on when exactly it happens.

Check the axle shaft ujoints at the knuckles.  These operate at a higher angle when turning and will cause pulsing at angles if they are stiff or worn.  Pull the unit hub and shaft and work the joint by hand to see how it feels.  Most likely a stock joint with 150K miles you might as well replace them both.  Get origional Spicer brand joints online or at some Napa stores.

Just a tip:  You don't need to take the 36mm alxe shaft nut loose to just check them out.  I always just pull the hub and shaft as an assembly first.   Also do not drive the jeep with out a stub shaft in the hub, it can separate.

I have a growl in my front axle that is a rough unit hub.  You really have to jerk on the wheel to feel movement in the bearings, but it doen't take much.  Got to get it replaced this weekend.

ok, I have rambled on enough

Andy

Thanks for the info, very helpful. > some hopping in 4wd on solid surfaces is necesary. For the noise to change > when you are on the gas in 2wd would have no connection to the front axle. I should have clarified, I've swapped my XJ for a ZJ Grand Cherokee. It doesn't have a true 2WD mode but a permanent 4wd mode that is normally rear driven but shifts power up front when needed. Would the above still apply? > Guess I am just looking or more clarification on when exactly it happens. Generally all the time. It's very loud from about 5-10mph, still there from about 10-15 but is noticeably quieter, then builds with speed after that. It's so loud that it's uncomfortable at 70mph. Lifting off the gas for a second makes the noise drop for a moment then it starts again. I might be imagining it but it seems worse if the road is bending. > Check the axle shaft ujoints at the knuckles. These operate at a higher > angle when turning and will cause pulsing at angles if they are stiff or > worn. Pull the unit hub and shaft and work the joint by hand to see how it > feels. Most likely a stock joint with 150K miles you might as well replace > them both. Get origional Spicer brand joints online or at some Napa stores. I'm hoping it is the UJ's as they are fairly cheap here (I'm in the UK, big parts are horrendously priced). > > Just a tip: You don't need to take the 36mm alxe shaft nut loose to just > check them out. I always just pull the hub and shaft as an assembly > first. Also do not drive the jeep with out a stub shaft in the hub, it can > separate. I'll have a go with that, thanks for the tip. > > I have a growl in my front axle that is a rough unit hub. You really have > to jerk on the wheel to feel movement in the bearings, but it doen't take > much. Got to get it replaced this weekend. I'll take another look. I'm planning on swapping the hubs out anyway as I noticed they were badly corroded when I was doing the brake pads. I haven't had the truck long enough to give it a real going over so I'm just catching up with everything. Cheers, Stuart

The ZJ case is a full time 4wd setup.  Alot of times they do not use regular u-joints in the front axle but CV joints with rubber boots.  They are not really servicable and you replace the entire assembly.  I have heard they  are pretty reasonable from most auto parts stores.  the balls inside the CV can get rough or the cages or bels can crack and cause noise.

Those full time only cases are also known for some problems.  There is a viscous coupling inside the case that spits power between the front and rear outputs.  This coupling is known for going bad and can also cause noise when just a front or rear tire breaks traction.

Hope some of that helps.

Andy


On 11/9/06, boristhepenguin <

Hi Andy, thanks, it's all very helpful. my ZJ has CV joints on the half shafts. The boot on the left CV joint had failed and you can hear the background noise from that, but the grinding is on top of this. I've got a new half shaft on order, the price is OK, about $60 for the full assembly -- local Jeep dealer wants approx $40 just for the replacement boot so I figured I might as well replace everything. The noise seems to be coming from up front rather than the transfer case. Checked fluid levels tonight, they're ok but the diff oil looks terrible, like green paint. I'm going to change the diff oil at the weekend. I've had suggested so far: driveshaft UJ's, CV/half shaft, wheel bearings and the diff bearings. Apart from the wheel hubs there are no hugely expensive parts so I'm just going to do them all. At 150k miles swapping all these out isn't going to hurt. I just hope it cures the problem. Many thanks, Stuart

Just a side thought here:  Check your engine mounts.  I had a 93 ZJ that they sagged out on.  Under throttle the whole body would buzz due to the engine vibration being transfered.

You are there with your ears though.  Kinda hard to describe noises in type ain't it.  lol.

Andy

I had similar problem (with additional clicking sound when going very slow n turning) ... turned out the front wheel spindle+bearing assembly (on XJ) was defective even though it was a brand new one (Omix brand). I replaced it with Mopar ... problem gone. I'd never buy Omix again ... ... another thought, power steering pump, pulleys?