Jeep Renegade Forum banner
601 - 618 of 618 Posts

· Registered
Joined
·
4 Posts
2017 Renegade, 1.4 turbo, 6 speed manual. 42k miles. I have owned this vehicle for 3 years. As many and myself have described, like clockwork noise starts at 38 mph and goes away at 43 mph. I recently took a 900 mile trip/2 day trip with this vehicle. On the highway at speed, (65-70), this disturbing noise would appear for 2-3 seconds and then go away. It didn't happen often. Over 900 miles it may have done it 4-5 times. I have no idea what may be engaging or disengaging to cause this or why. I thought I heard this noise before at speed but it happens so infrequently I thought it may have been a rough road patch. This trip showed it to be otherwise.
 

· Registered
Joined
·
28 Posts
INCREDIBLE that any automaker would ignore so many concerns on the same issue.
This must be due to their incompetence as engineers to resolve such an annoying problem.
If we could tally the many sales that have been lost due to the "Renegade Rumble" it would get their attention.
We're complaining becasue we haven't walked away - yet. Those who have don't complain after leaving.
So... Anyone up to figure out what this has cost FCA?
 

· Registered
Joined
·
279 Posts
Tool Camera accessory Auto part Machine Engineering



If you look at this cutaway image of the rear diff, you'll see the multi plate wet clutch on the right. These are interleaved friction discs, where every other one is connected to the ring gear & input shaft (lower left), and the others are connected to the differential.

The only difference in this assembly when the grinding noise is heard is that the input shaft & ring gear are stationary, and therefore every other disc in the clutch pack is stationary. When the input shaft is spinning there is very little speed difference between the discs. The noise cannot come from the input shaft or ring gear, or their bearing, because it happens when they are stationary. Therefore the noise comes from the clutch pack.

I noticed the other day that when the grinding noise occurs the entire floor resonates like a sounding board, yet the entire rear diff and suspension is attached to the chassis with rubber isolators/bushings. Maybe the problem isn't that the diff is resonating/vibrating, but rather that the bushings have failed - just as the motor mounts fail and allow engine vibrations into the chassis. I'll be looking at those isolators on mine this weekend if I can spare the time.

Also, some are discussing a "clunk" - not sure what that is, but it sounds more like some transmission issue.
 

· Registered
Joined
·
279 Posts
SOLVED! At least for mine. The problem is once again a floppy rubber isolator that has lost its support.

All of the rear subframe and diff support bushings seemed fine. That left the center driveshaft support to be examined, and it was a major suspect since it's connected to the rear diff input, and therefore to the clutch pack which must be the source of the vibration. Clearly there was also a mechanical resonance occurring. I noticed the drive shaft is light and that when shaken there was a rattle at the center support. If you gripped it solidly enough the rattle was damped out - but of course it must be able to spin. It was also really easy to move it around in the rubber bearing support, so I figured maybe if that rubber part were stiffer it would damp out that rattle.

I found that there is a fairly deep groove around the center bearing towards the rear, and I was able to cut a piece of 5/16" fuel line to an appropriate length, and pack it into that groove. Took it for a drive and the groaning/growling vibration is gone.

I have no doubt that the line I packed in there will fall out eventually, so when it is warmer I will glue it in with some urethane adhesive.

Automotive tire Tire Wheel Bicycle part Rim



Automotive tire Tire Wheel Bicycle part Rim


Automotive tire Wood Font Pattern Auto part

Automotive tire Wood Font Pattern Auto part
 

· Registered
Joined
·
279 Posts
Minor correction - the groove I packed the tubing into faces the front, not the rear.

We drove it going out to dinner last night and it was so much nicer to drive. It was a bit warmer today, and I realized I had a can of rubber cement for tire patches and the like which had a brush in the lid. I brushed it all around the tubing in the hopes that it will hold it in place. There really isn't much force trying to push it out, it's just the the bottom of a vehicle is a nasty place......
 

· Super Moderator
Joined
·
3,697 Posts
Does anyone have a fix? Mine just started slamming while slowing down under 40 :(
That's not related to this problem, and you should probably take it in for service.


INCREDIBLE that any automaker would ignore so many concerns on the same issue.
This must be due to their incompetence as engineers to resolve such an annoying problem.
If we could tally the many sales that have been lost due to the "Renegade Rumble" it would get their attention.
We're complaining becasue we haven't walked away - yet. Those who have don't complain after leaving.
So... Anyone up to figure out what this has cost FCA?
Well they haven't totally ignored it. There is a firmware fix for the 2.4L that pretty much gets rid of it. At least it did for me. I think the issue is that to address it, they have to do things that affects their EPA estimates they submitted to the government, so they avoided it for a while. There was supposedly a firmware fix years before it went public, but it wen't poof just about the time FSA started getting investigated by the EPA. However, the 2.4L oil consumption problem forced them to muck with things that change the EPA emissions estimates and suddenly there is also a 2.4L fix for the rumble. But not for the turbo motors.

View attachment 2396355727


If you look at this cutaway image of the rear diff, you'll see the multi plate wet clutch on the right. These are interleaved friction discs, where every other one is connected to the ring gear & input shaft (lower left), and the others are connected to the differential.

The only difference in this assembly when the grinding noise is heard is that the input shaft & ring gear are stationary, and therefore every other disc in the clutch pack is stationary. When the input shaft is spinning there is very little speed difference between the discs. The noise cannot come from the input shaft or ring gear, or their bearing, because it happens when they are stationary. Therefore the noise comes from the clutch pack.

I noticed the other day that when the grinding noise occurs the entire floor resonates like a sounding board, yet the entire rear diff and suspension is attached to the chassis with rubber isolators/bushings. Maybe the problem isn't that the diff is resonating/vibrating, but rather that the bushings have failed - just as the motor mounts fail and allow engine vibrations into the chassis. I'll be looking at those isolators on mine this weekend if I can spare the time.

Also, some are discussing a "clunk" - not sure what that is, but it sounds more like some transmission issue.
The only problem with the rubber isolator theory is that this happened in vehicles from new. Mine did, and it did it after a rear drive unit replacement. If the bushings were beat, they wouldn't put them back. The point of the wet clutch is to have varying levels of slip/engagement by managing the clutch engagement. The operating theory for a long time is that it isn't as disengaged as it's supposed to be due to the traction control strategy. It'd just likely be even louder without the rubber isolators. It also isn't shocking that the vibration is transmitted through the drive shaft to an extent since it is mechanically coupled to the RDU.
 

· Registered
Joined
·
279 Posts
The only problem with the rubber isolator theory is that this happened in vehicles from new. Mine did, and it did it after a rear drive unit replacement. If the bushings were beat, they wouldn't put them back. The point of the wet clutch is to have varying levels of slip/engagement by managing the clutch engagement. The operating theory for a long time is that it isn't as disengaged as it's supposed to be due to the traction control strategy. It'd just likely be even louder without the rubber isolators. It also isn't shocking that the vibration is transmitted through the drive shaft to an extent since it is mechanically coupled to the RDU.
You are confirming my theory. The bushing I'm discussing is the center support for the driveshaft and would not need to be removed or replaced to remove the RDU - and likely why replacing the RDU didn't fix yours. It still has the same center support isolator.

The vibration source must be the wet clutch itself - whether that's because it is not fully disengaging and is therefore dragging, or some other design issue I couldn't tell. However, that should not be causing the entire floor to vibrate strongly like mine did. While riding in the passenger seat I could feel it vibrating right below my feet - right about where the driveshaft center support is located. The driveshaft is clearly resonating, making the vibration much worse, overwhelming the center support isolator and transmitting that resonance to the floorpan. Ironically the center support isolator needs to be stiffer to prevent an undamped oscillation of the driveshaft.

We bought our Renegade used, so I have no idea if it did it from new, but I noticed it not long after we bought it. When I changed the fluid in the RDU it was quite clean, so I doubt it is a wear issue, and so I suspect it was always that way. Note that I was not really suggesting the isloator wore out, rather I think many of the rubber isolators (motor mounts, exhaust hangers, this driveshaft support) were poorly designed and simply don't work well.
 

· Registered
Joined
·
279 Posts
I drove it to work today, about 60mi round trip. On the way home the noise came back, so I checked it when I got home. The tubing had worked out out of the groove somewhat. It has to be firmly seated, and most importantly it has to be snug against the inner rubber snout that holds the bearing.

I'll be working on a way to secure it in the groove, or perhaps a better tubing, but this is definitely the right track.
 

· Super Moderator
Joined
·
3,697 Posts
You are confirming my theory. The bushing I'm discussing is the center support for the driveshaft and would not need to be removed or replaced to remove the RDU - and likely why replacing the RDU didn't fix yours. It still has the same center support isolator.

The vibration source must be the wet clutch itself - whether that's because it is not fully disengaging and is therefore dragging, or some other design issue I couldn't tell. However, that should not be causing the entire floor to vibrate strongly like mine did. While riding in the passenger seat I could feel it vibrating right below my feet - right about where the driveshaft center support is located. The driveshaft is clearly resonating, making the vibration much worse, overwhelming the center support isolator and transmitting that resonance to the floorpan. Ironically the center support isolator needs to be stiffer to prevent an undamped oscillation of the driveshaft.
I think you may have multiple issues, and many others may too. But I've never mucked with that bearing or bushing, and mines essentially gone now. Also even when mine got BAD, you could never feel it in your feet anywhere and the noise was centered left to right in the cargo area just behind the rear seat back. Basically right above the RDU.

Like a lot of FSA stuff, the parts sourcing is probably bad and there's a lot more variance in the actual parts than the engineers designed for.

I suspect you are right that it is contributing to the how pronounced it is in your case (and likely others), but I'm pretty sure it won't make it go away, just make it less prominent for those with that flavor of the problem.
 

· Registered
Joined
·
279 Posts
I think you may have multiple issues, and many others may too. But I've never mucked with that bearing or bushing, and mines essentially gone now. Also even when mine got BAD, you could never feel it in your feet anywhere and the noise was centered left to right in the cargo area just behind the rear seat back. Basically right above the RDU.

Like a lot of FSA stuff, the parts sourcing is probably bad and there's a lot more variance in the actual parts than the engineers designed for.

I suspect you are right that it is contributing to the how pronounced it is in your case (and likely others), but I'm pretty sure it won't make it go away, just make it less prominent for those with that flavor of the problem.
If you've ever experienced a bad motor mount (or a race car with solid mounts), you know how awful the vibration can be - and yeah, you can feel it too. Is the engine bad? Well no, they just vibrate a lot. I found that the noise was pretty well gone when the fuel line was packed in tight.

It's also quite reasonable to assume there is variation, both in the driving vibration in the clutch pack, as well as the resonance of the driveshaft and the characteristics of the center support bushing. As far as I know some vehicles don't do it at all. I've been dealing with manufacturing issues for over 30 years, and this stuff is typical.
 

· Registered
Joined
·
279 Posts
So I took another shot at it today. I removed the tubing and noticed it had flattened somewhat, which is no surprise as it was not designed to hold shape in compression. I decided I should look for something to insert into the the tube to give it more strength, and found an old power cord that was just the right diameter. Once I had that together I put a layer of RTV (Permatex Ultra Gray) on the outer and inner walls of the bushing, and then pushed the tubing into the slot. Then I filled in more RTV on the surface. Note that the slot is towards the rear, I just kept remembering it wrong.

Anyway, I put a heater under it and let it set for a few hours, then took it for a drive. Big mistake! I made it way too stiff/rigid, and you could hear and feel everything going on down there, from engine vibrations coming down the driveshaft to the clutch opening up, and the clutch vibration that is the source of this whole problem. It didn't really resonate the way it had, just could feel and hear it. That was unacceptable so I pulled it apart again (the RTV was not totally set yet).

I put it back with a fresh piece of tubing with nothing in the center. I think it's an acceptable compromise. On occasion I can hear the vibration between 40 and 45mph, but it's much more damped and does not shake the floor. Most of the time you don't hear it at all. Not sure what the random element is - perhaps the position the draveshaft stops in? Anyway, it's one heck of a lot better than it was.

I have no doubt that this bushing/isolator could be tuned so that it never does it, but I don't have that kind of time to spend on it. Time will tell if the rubber tubing crushes down and stops damping out the driveshaft.

The fuel line I used is about 0.560" OD. I tried some 0.625" stuff, but that was too wide to go in.
 

· Registered
Joined
·
279 Posts
Just going to throw this out there... Have you considered your bearing/bushing combo is beat and you just need a new one? There are even third party ones that look like they might have more shock absorbing material than the OEM version.
It's always possible the bushing is shot, although there are no obvious signs of damage. The bearing however cannot be a problem, as the noise happens when the shaft/bearing is not spinning. Do you have any links or info on 3rd party parts?

Overall I think the bushing was designed to filter out normal driveline noise, without consideration for the vibration from the rear diff clutch unit. Pretty sure that's not supposed to be there.
 

· Super Moderator
Joined
·
3,697 Posts
It's always possible the bushing is shot, although there are no obvious signs of damage. The bearing however cannot be a problem, as the noise happens when the shaft/bearing is not spinning. Do you have any links or info on 3rd party parts?

Overall I think the bushing was designed to filter out normal driveline noise, without consideration for the vibration from the rear diff clutch unit. Pretty sure that's not supposed to be there.
Here's an example. Different format than OEM that doesn't use the square housing.


Also if you go digging far enough back, there was a run of bad drive shaft bearings in the past resulting in clunks accelerating and stopping IIRC.
 

· Registered
Joined
·
279 Posts
Here's an example. Different format than OEM that doesn't use the square housing.


Also if you go digging far enough back, there was a run of bad drive shaft bearings in the past resulting in clunks accelerating and stopping IIRC.
Thanks - I'll look at those. I wish I had a FSM as I don't know how the driveshaft comes out or comes apart at this point.
 

· Super Moderator
Joined
·
3,697 Posts
Thanks - I'll look at those. I wish I had a FSM as I don't know how the driveshaft comes out or comes apart at this point.
I've got the full priced legit service manual, and I've got the $15 ebay version. The $15 ebay version is more complete and searchable. IT also doesn't require internet explorer to still exist. The legit version just has a functional TOC if I know what I'm looking for and where it is exactly.
 
601 - 618 of 618 Posts
Top