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I'll Direc your TV
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Discussion Starter #1
Have a 2006 Jeep Grand Cherokee, 4.7L, 4x4.

Been having this issue for a while, and attempted to fix it a few months ago; but now it's persisting (sucker didn't fix itself), with the new camper I want to get it fixed before I tow it with the jeep

The issue is a rattling sound when under load (towing a trailer, hitting to gas pedal, etc). Does not do it all the time, but most of the time, and it's quite loud (can hear it at my house when my wife goes and leaves down the road). It is a legitimate rattling, almost exactly if you took a wrench and rattled it between two sections of frame rail really quick.

Just got done looking at it further, and i'm still kinda stumped. I believe it is goming from the front drive train; either drive shaft, differential, or cv shafts. What I saw what the front shaft and differential shake what seemed quite a lot, the shaking didn't really seem to coincide with the sounds of the rattling, so I think they were two different things. For the front differential; It has new mounts/bushings, I replaced them last year, the front one and passenger one; the top bushing (which is a known issue of these jeeps) was replaced when we bought the jeep, in 2015? 2016? either way, it was replaced too. Both CV shafts were spinning, like seemingly normally with the tires, they're both solid and no updown/sidexside movement. The front shaft U-joints are solid, no play on either end.

I believe it is NOT:
Exhaust
Rear Shaft
Transmission
Engine Mount
Transmission Mount

Reasoning for the not mounts is, they look fine, and they do not move excessively when pried on; plus there is zero drive-ability issues, or running/shifting issues. Literally it is a sound, albeit a very loud one.

I am thinking it is a f'd up front differential; though I changed the fluid (I think I did anyway) and I don't remember there being any metal in it; That is the only think that makes sense, so I think the only way to know for sure is to take it out, and take it apart.

Anything else I should look at? Anything further I should to do diagnose more? Not sure what else to do. Also, to diagnose it, I put the jeep up on jack stands and had my wife sit in it, and engage the brake a little while giving it some gas, to simulate a load on it. It does this going down the road only while accelerating, just coasting or going the same speed it does not do it; it also does not do it while driving slowly or under very light load.
 

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Gustafson
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I don't recall seeing if this sound gets faster or slower, i.e. changes with speed or engine RPM?
 

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I'll Direc your TV
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Discussion Starter #3
I don't recall seeing if this sound gets faster or slower, i.e. changes with speed or engine RPM?
It gets faster/louder with more engine RPM, but when you let off the gas to coast, or stay a steady speed it goes away. If you let off the gas, then accelerate slowly it does not happen.
 

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Premium Member
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2,435 Posts
Being a 4.7 you may have guides and a timing chain getting ready to take a poop. Just a thought.
 

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I'll Direc your TV
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8,557 Posts
Discussion Starter #5
Being a 4.7 you may have guides and a timing chain getting ready to take a poop. Just a thought.
I thought about that, however the sound isn't seem like it's coming anywhere near the timing chain area. And there are zero issues with the engine; no running, starting, towing, mpg ....etc issues.

Still could be an engine issue, however i'd think that it would happen all the time, or more often than it does.
 

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I thought about that, however the sound isn't seem like it's coming anywhere near the timing chain area. And there are zero issues with the engine; no running, starting, towing, mpg ....etc issues.

Still could be an engine issue, however i'd think that it would happen all the time, or more often than it does.
Cracked or broken flex plate maybe.
 

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I'll Direc your TV
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Discussion Starter #8
Catalytic converter or a heat shield rattling?
checked that, cat seems to be running normally, normal temps going in and out, and no shakky heat shield
 

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It gets faster/louder with more engine RPM, but when you let off the gas to coast, or stay a steady speed it goes away. If you let off the gas, then accelerate slowly it does not happen.
My wife had the same thing with hers. I never noticed it and she never mentioned it. One day I take it to the store for a spin, you know to burn some carbon out and as I got on it a little more than normal it did the same thing, only under load. Drive it normal and everything was fine.
Never did find out what it was and she eventually sold.
 

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I'll Direc your TV
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Discussion Starter #12
I want to say that it happens more when you turn to the left; might just be me looking for something, but I feel like it happens more steadily.

I am going to first take off the diff cover to check the gears, i don't feel pinion play when I push up on the front driveshaft, but that doesn't mean it's not loose. If I don't see anything obvious then I plan on taking out the whole diff and checking it over completely; and for sure checking/replacing the upper mount bushing.
 

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Desert Rat
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7,062 Posts
So, back in the day, 1995 or so I picked up a really cool Jeepster Commando, axles flipped and springs arched, with what the owner said had a real bad rod knock, for $500. It was that jeep mint green color.

After sitting over the winter, I planned to put a LT1 in it. When crawling around making plans I discovered all but one torque converter bolts had fallen out. I R&Red all the torque converter bolts with locktite, drove it for six months with a for sale sign on it and turned a nice profit.
Check the TC bolts.
 

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Catalytic converter or a heat shield rattling?
I haven't had my Jeep in quite a while but, my '99 TJ had a mystery knock for about five years. It only knocked after I started it up, drove it enough to warm it up and only when it was warm outside.

When I had my husband try to figure it out with me he kept thinking a lot of those things that you have listed - same with my mechanic. So, one day when I was on the way home from work I stopped at the gas station that's 3 miles from our house. Upon restarting the knocking was there again and scared some people at the pumps. I just laughed and said 'it hasn't blown up yet' and drove off. I left it running in the driveway and we listened to it.

I was insisting that it was coming from just in front of the driver within a few inches of the inside of the engine compartment. We took it to the mechanic and left it there for a few days. I pointed out where I was sure it was coming from. He told me it was probably serious and he'll let me know how much it's gonna cost me before he does any work.

Three days later I got a call that I could come pick it up. I got there, my bill was $0 and I was right. It was a heat shield that was expanding with the heat under the hood and it was knocking on the head of a bolt. The bolt next to the housing wasn't screwed in all the way.

No more knocks for the rest of the years I had it - 16 altogether.

Just my girly guess but I was right once. My dad raised me to know things but things are a lot different now.
 

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I'll Direc your TV
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Discussion Starter #15
Can't hurt to check. A bolt may have back out, few years ago I had both manifolds replaced as the studs had broken off (per normal jeep WK engines)

I have yet to do anything major...so I will do the easy to do stuff first, heat shields, check the cat again (haven't done it in a while). If the cat is rattling, how can I check it other than doing a temp test?
 

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I'll Direc your TV
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Discussion Starter #16
Bringing up an old thread because I am still chasing the same issue; though now I believe that most of the problem is solved.

Could not for the life of me figure out the issue, so I ended up taking it to a shop, long story short, they replaced Drivers' upper a arm, both strut fork bushings, passenger lower control arm, CV shaft, front differential, $1,000 later....still had a rattle/knock but it was mostly gone.

Fast forward to a couple weeks ago, wife said that there was another loud rattle coming. Drove the jeep myself and it was a rattle under load and was loud as all get out, but not all the time. So, I did the right thing and left it alone for a while.

Then, while doing a brake change, and oil change, I noticed that my air intake tube was pulled part, like it wasn't clamped down or not put together completely; not sure why that would have happened, but I chalked it up to mouth breathers at Pennzoil since the wife took it there for a quick oil change a bit ago. Later on, more rattling, clunking, and I start to think ok, should probably do something about this. Looked at it, and it's not u joints which I was hoping it is, and was pretty sure it was not the flex plate, as no drivability issues. So, using my keen sense of remembering what I forgot, I thought about the air tube and wondered...hmm, motor mounts might actually be shot. Sure enough, going from D to R with foot on the brake, the motor jumps like its in a pogo stick contest. So those are getting replaced, along with eventually the D lower ball joint, and sway bar bushings. Shop is doing the motor mounts, cause you close near have to yank the whole motor out, and I don't want to do it in a garage, then i'm doing the ball joint and sway bar bushings.

Hoping, and assuming that will finally solve the nearly year long rattle, clunk, $$$ sounds coming from the jeep.
 

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Gustafson
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9,597 Posts
Well, by the time you're doing figuring out what it is, the whole jeep will be rebuilt....haha. Hopefully the motor mounts solve the problem.
 

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I'll Direc your TV
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Discussion Starter #18
Well, by the time you're doing figuring out what it is, the whole jeep will be rebuilt....haha. Hopefully the motor mounts solve the problem.
Motor mounts seemed to have solved the problem! Though there still is the issue of needing ball joints and swar bar bushing, but at least the main issue seems to be ok.

The jeep really doesn't owe me anything at this point, 242,000 miles and still going strong. Hope to keep it going past 300,000 too. I've got the ball joints and bushing going in this weekend when I get time to do it. Then maybe I can actually get an alignment done on it.
 

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Gustafson
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9,597 Posts
Motor mounts seemed to have solved the problem! Though there still is the issue of needing ball joints and swar bar bushing, but at least the main issue seems to be ok.

The jeep really doesn't owe me anything at this point, 242,000 miles and still going strong. Hope to keep it going past 300,000 too. I've got the ball joints and bushing going in this weekend when I get time to do it. Then maybe I can actually get an alignment done on it.
Awesome!! Glad it worked.

It should make it to 300k. You really don't do stop and go driving (I assume) and that is one of the hardest things on the parts.
 
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