2001XJSC

I just recently purchased an 01 XJ Classic (4.0, Auto, NP242). It's got a slight growling noise coming from the front end driveline somewhere right under the dash. Seems to be loudest around 20-50 mph usually on deacceleration. (could just hear it more because the engine isn't making much noise). I've noticed if I grease the zerk fitting on the front driveshaft, the noise is almost gone. This lasts about 2 days, and then the noise comes back. If I regrease this zerk again, it takes a few pumps of grease before it starts coming out of the end of the driveshaft, and then the noise is good for another few days.

What exactly is this zerk greasing on the front driveshaft? Is this a common area for noise? The U-Joints seem solid, no play or obvious wear. ( I might go ahead and replace them as they look original, just curious why greasing the zerk cures the noise for a few days)

Thanks!

Jeepwalker

Well, could a few things to do with the driveshaft:
1) Slip yoke worn - After you drive it and it vibrates, park it (in Neutral) and wiggle up/down as hard as you can with your hands. It shouldn't move at ALL at the slip yoke. If it does, it's worn and needs to be replaced. This is quite common. It sounds like when you pump it with grease it's filling the void where it's worn, and momentarily stops vibrating, until it overcomes the grease and starts vibrating again. It's a common issue when people don't grease the slip joint or drive in deep water. If that's the cause, just buy a new driveshaft.
2) Worn CV (constant velocity) stud or bearing. - This is at the back of the driveshaft between the two u-joints. There's a ball on a stud between them. You can't really see it. Where the ball fits over the stud, there's a caged needle bearing that fits over the stud and goes inside a hole in the ball ....which many owners don't grease. When the bearing wears out it can cause driveshaft vibration ...and even exacerbate wear on the front yoke (and vice versa). If the slip-joint is tight, the CV can be replaced, but it's not a job for someone who doesn't have a fair amount of experience. If you have to pay someone to change it, you might as well consider buying a new driveshaft.
3) Bent driveshaft - Not likely, but possible. Especially if it's been 'wheeled' a lot. Also if a weight falls off.
4) Bad U-joint - Check the back u-joints too.

Besides these, check the outside axle u joints, the front tires (for out of roundness), rims (for bentness), pinion (for being loose), tie rod ends, and the shocks for oil leaks or missing bushings.

Romans715

I believe this is what's happening to my 1994 XJ 4x4 4.0. it is a clicking sound similar to a chain rattles on a bike. When I am sitting still it does not make a sound. When I am moving I can hear it especally over 15mph. I'm going to check where this other poster has said to look. And maybe look at my transfer case.

Jeepwalker

Basically, as a rule, if the driveshaft has noticable movement when you vigorously push up/down (vehicle in N), then the driveshaft is worn. A very small amount of movement is acceptable on a high mileage rig ...at normal highway speeds, but at some point and at greater speeds it becomes noticeable as it becomes worse. Outer axle u-joints which are worn often 'click' at low speeds. Check them carefully with a pry bar (again, vehicle in N). If they show movement, they're worn, don't let them get ahead of you.

2001XJSC

Jeepwalker, thanks for the advice!

I don't have any vibrations, jeep drives straight and smooth on the highway other than the whirring/growl sound mentioned above. I'll definitely check the slip joint/slip yoke on the front driveshaft for wear.