What can this front-end thunk be??

[NewJeepr]

Ok, my mechanic is stuck - and he is usually excellent. So I will send this out to the collective wisdom.

I have a 2000 Jeep Cherokee Classic. All stock. Bought it about 15 mos ago with 35k; it now has 52k on the clock. No problems until last month. Goodyear Wrangler tires in fairly good shape.

Drove it from Philadelphia to Colorado Springs in 3 days last month. Then drove it about 150miles over the next 4 days, then back from CO (3 more days driving). Jeep drove like a champ - 25mpg, too! Changed the oil before I left & when I got back.

Within a few days of my return from CO (& I'm not even sure it has anything to do with the problem), I started hearing an intermittent rhythmic clunking sound from somewhere up front, as the vehicle moves. Intermittent in that I don't hear it each time I drive the vehicle. But once it starts, I hear it for the entire trip, as described below.

It starts once the vehicle is warmed up. If I am going under 30mph, I can hear it when I am coasting. I can also hear it when I am gently applying the gas; the engine sound seems to drown it out when I am seriously accelerating. But it totally stops when I apply the brakes. The frequency of the thunking is directly related to how fast I am driving.

I also hear it when I have the all wheel drive engaged. I can hear it from both the driver's and passengers seat. Both my husband and my mechanic have heard it as well. It may be going on while going over 30; but I can't tell if the engine/road noise is drowning it out or it stops over 30.

No change in braking, steering, no pulling or anything else. No difference in the ride quality. Just this clunking sound. My mechanic checked underneath and could not find anything loose, dry, needing lubrication, etc. He lubed everything possible, but the sound continues. Tires are ok; no lost balance weights on the rims. I can feel it thru the steering wheel.

Any thoughts?

newjeepr

[kensxjon37s]

Originally Posted by NewJeepr

Ok, my mechanic is stuck - and he is usually excellent. So I will send this out to the collective wisdom.

I have a 2000 Jeep Cherokee Classic. All stock. Bought it about 15 mos ago with 35k; it now has 52k on the clock. No problems until last month. Goodyear Wrangler tires in fairly good shape.

Drove it from Philadelphia to Colorado Springs in 3 days last month. Then drove it about 150miles over the next 4 days, then back from CO (3 more days driving). Jeep drove like a champ - 25mpg, too! Changed the oil before I left & when I got back.

Within a few days of my return from CO (& I'm not even sure it has anything to do with the problem), I started hearing an intermittent rhythmic clunking sound from somewhere up front, as the vehicle moves. Intermittent in that I don't hear it each time I drive the vehicle. But once it starts, I hear it for the entire trip, as described below.

It starts once the vehicle is warmed up. If I am going under 30mph, I can hear it when I am coasting. I can also hear it when I am gently applying the gas; the engine sound seems to drown it out when I am seriously accelerating. But it totally stops when I apply the brakes. The frequency of the thunking is directly related to how fast I am driving.

I also hear it when I have the all wheel drive engaged. I can hear it from both the driver's and passengers seat. Both my husband and my mechanic have heard it as well. It may be going on while going over 30; but I can't tell if the engine/road noise is drowning it out or it stops over 30.

No change in braking, steering, no pulling or anything else. No difference in the ride quality. Just this clunking sound. My mechanic checked underneath and could not find anything loose, dry, needing lubrication, etc. He lubed everything possible, but the sound continues. Tires are ok; no lost balance weights on the rims. I can feel it thru the steering wheel.

Any thoughts?

newjeepr

check the u-joints in the axle shafts.

[NewJeepr]

Hi Ken,

My mechanic checked that first thing & even lubed them, but the noise still persists. Can that happen? Any other thoughts?

Thanks

Mary

[SteelHeadz]

The u-joints on the axle shafts are a sealed unit. I don't think its possible to lube them on the vehicle. I would look at that a little bit closer.

[CanadianDave]

I have a 2005 Grand Cherokee. My wife has been complaining about the same or a similar clunk in the left front. It comes and goes, but once it comes, it stays for the entire trip. It did it last winter, I thought it was ice buildup on a shaft, CV or joint. It didn't do it all summer, now it did it yesterday. i took it last night, it didnt do it. I have grabbed every shaft, joint, union, etc., and shook them like crazy and nothing appears to be the least bit worn. Last winter i took it to the dealer, they blew 1/8 tank of gas driving around and couldnt replicate it. Back then I found putting the trans in neutral, then coasting at about 20 mph made it happen more pronounced. You can feel the clunk when it does it. If the noise was elsewhere, it would feel like the transfer case chain riding up the sprocket.
I don't know jeep 4wd systems, is there a locking hub or a clutch somewhere that could be failing to totally engage or release?

	Transfer Case Mounted behind and driven by the vehicle transmission, the transfer case transmits power to the front and rear driveshafts in 4WD Jeep vehicles and offers high and low range.

[SteelHeadz]

Originally Posted by CanadianDave

I have a 2005 Grand Cherokee. My wife has been complaining about the same or a similar clunk in the left front. It comes and goes, but once it comes, it stays for the entire trip. It did it last winter, I thought it was ice buildup on a shaft, CV or joint. It didn't do it all summer, now it did it yesterday. i took it last night, it didnt do it. I have grabbed every shaft, joint, union, etc., and shook them like crazy and nothing appears to be the least bit worn. Last winter i took it to the dealer, they blew 1/8 tank of gas driving around and couldnt replicate it. Back then I found putting the trans in neutral, then coasting at about 20 mph made it happen more pronounced. You can feel the clunk when it does it. If the noise was elsewhere, it would feel like the transfer case chain riding up the sprocket.
I don't know jeep 4wd systems, is there a locking hub or a clutch somewhere that could be failing to totally engage or release?

It's likely to be the coupler in the T.case.

	Transfer Case Mounted behind and driven by the vehicle transmission, the transfer case transmits power to the front and rear driveshafts in 4WD Jeep vehicles and offers high and low range.

[54cj3b]

I was wondering the same thing the other night ..
next day went out to check Ujoints to find a dead skunk wraped around front drive shaft

BOY DID IT STINK

[NewJeepr]

Snipped: The u-joints on the axle shafts are a sealed unit. I don't think its possible to lube them on the vehicle. I would look at that a little bit closer.

Hi Ken, Thanks- I'll check it out further. I may have misunderstood what the mechanic said.

[volaredon]

Originally Posted by NewJeepr

Snipped: The u-joints on the axle shafts are a sealed unit. I don't think its possible to lube them on the vehicle. I would look at that a little bit closer.

Hi Ken, Thanks- I'll check it out further. I may have misunderstood what the mechanic said.

If they are original, that is true but many of the aftermarket replacements are greasable; the outer axle wheel joints are commonly bad. also check the sway bar links if they have a "tie rod" type end on their top ends where they bolt to the sway bar.

	Swaybar A sway bar (also stabilizer bar, anti-sway bar, roll bar, or anti-roll bar, ARB) is an automobile suspension device. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness—its resistance to roll in turns, independent of its spring rate in the vertical direction.