The Telltale Clunk

Jeepman said:

The original sway bar bushing for the 4th Generation was a straight synthetic rubber bushing. It was only about 2005, maybe earlier, that the "nylon" insert showed up within the same rubber bushing to try to solve the noise problem. In the meantime MOOG had the thermoplastic blue bushing, which was used with some success.
Perhaps the wear and tear on the rest of the suspension causes a looseness and more travel and is the straw that breaks the back of a marginal design. The factory installed system seems to perform well for years.
At one point, over the years, a bushing with a fabric interface was marketed, obviously looking for more friction (grab). That type of design seems to be coming back (MOOG).
At another point the Mopar bushing, with the white insert, had a white paste between the bushing and the insert. That didn't last long either.
So, the OE bushings have taken on a life of their own. At least three different designs.

Click to expand...

Thanks. This history ought to be a sticky. I don't think there is any doubt you are correct that they were meant to compression grip the bar. It also seems there is no doubt they failed to come up with a design to do that on any sort of long term basis especially once the suspension wears in.

So it seems we are all stuck with workarounds with parts that either mimic the original grip or toss the idea and let the bar rotate. As you say letting them rotate is not likely a great solution since there are various transient vibrations that were designed into the bar that was gripped that you will loose if you let it rotate. But gripping seems an elusive end with after market parts.

So ... for me my bar was polished smooth by the worn our blue poly Moogs so my guess is the cheap ones I replaced it with just weren't up to gripping well. The WD40 I sprayed on it ended the clunk by (another guess) by letting the bar rotate. That won't work for long because either the bushing will quickly wear out of the WD40 will dry out. Still working now though.

A knowledgeable parts guy recommended a different brand black rubber that is wider and more importantly a larger Outside diameter that will in theory grip better. That's my next try. I also got the Moogs with the white nylon insert. The instructions specifically say, "Do not apply lubricant to sway bar or bushings". I don't know what Moog had in mind but generally nylon is intended to be a self lubricating bushing intended to let things rotate. If they clunk I'll try lubing them and see what happens.

In short everyone seems to get this problem and most every fix tried works in the short term and none work in the long term. I'm just going to mess with it till I get something that last a year (ten thousand miles for me) and just keep replacing them. It's great to be retired with time on my hands.

REVOLUTIONary2B said:

With the links off, the bar ends freely move up and down around 6”. It has to to follow the suspension as it works. They could not be designed to be fixed at the bushings. It is not a torsion bar. Think of going over a speed bump perfectly straight at speed…both front struts will move up and down equally at the same time, and both ends of the bar will travel with them, unstressed.

Click to expand...

Wrong! Of course the sway bar will move up an down freely when the bushing is worn and not doing its job. Think NVH (noise, vibration, harshness). It's considerably worse when a sway bar bushing is no longer gripping the bar.

When the bushing is worn, the bar will rotate easily, without being grabbed by the bushing, and will move laterally from side to side as well. Both those movements compromise the purpose of the sway bar system i.e. to counter sway and to dampen down the suspension. NVH

The bar has no collars on it to prevent the sideways movement brought about by forces on the sway bar when steering the wheels. That movement can be seen when bushings are worn.

The only thing that prevents the bar from doing what it's not suppose to do (rotate loosely and slide loosely), is the grip the compression bond imposes between the bar and the bushing. Compression bonding is a common type of sway bar system design, it doesn't involve lubrication maintenance. Chemical bonding, used on some systems, is another type. Are you saying a sway bar is free to move in its bushing with a chemical bond? The bushing bites it's teeth and screws up its face. Compression bond and chemical bond both resist movement at the interface between the bar and the bushing. thereby affecting roll stiffness that a standard, free to move bushing design, doesn't. The free to move system design will also require lubricant, either by zerk or periodic maintenance of the lubricant (hard polyurethane bushings).

Sway Bar 101 from: Sway Bar Bushing Replacement
1. STABILIZER BAR WITH CONVENTIONAL BUSHING Note: Bar is loose within the bushing, decreasing the effectiveness of the bar. Also, the roll stiffness of the stabilizer bar with the conventional bushing is 17.7 N/ mm.
2. STABILIZER BAR WITH GRIPPY FLAT BUSHING Note: Flat surfaces on bar and bushing to create grip. Causes stress concentrations.
3. STABILIZER BAR WITH UPSET RING
4. STABILIZER BAR WITH CHEMICALLY BONDED BUSHING
5. STABILIZER BAR WITH COMPRESSIVELY BONDED BUSHING

Take your pick. Which one is it? The installation instructions from both MOOG and Mopar, for the Vans' sway bar bushings, say "install dry, no lubricant", time after time. The Parts guys at Mopar are vocal about that, no ifs, ands, or buts.

By the process of elimination:

• no chemical adhesive involved, scratch #4
• no upset ring, scratch #3
• no grippy flat surface, scratch #2
• no lubrication required, scratch #1

Jeepman said:

Wrong! Of course the sway bar will move up an down freely when the bushing is worn and not doing its job. Think NVH (noise, vibration, harshness). It's considerably worse when a sway bar bushing is no longer gripping the bar.

When the bushing is worn, the bar will rotate easily, without being grabbed by the bushing, and will move laterally from side to side as well. Both those movements compromise the purpose of the sway bar system i.e. to counter sway and to dampen down the suspension. NVH

The bar has no collars on it to prevent the sideways movement brought about by forces on the sway bar when steering the wheels. That movement can be seen when bushings are worn.

The only thing that prevents the bar from doing what it's not suppose to do (rotate loosely and slide loosely), is the grip the compression bond imposes between the bar and the bushing. Compression bonding is a common type of sway bar system design, it doesn't involve lubrication maintenance. Chemical bonding, used on some systems, is another type. Are you saying a sway bar is free to move in its bushing with a chemical bond? The bushing bites it's teeth and screws up its face. Compression bond and chemical bond both resist movement at the interface between the bar and the bushing. thereby affecting roll stiffness that a standard, free to move bushing design, doesn't. The free to move system design will also require lubricant, either by zerk or periodic maintenance of the lubricant (hard polyurethane bushings).

Sway Bar 101 from: Sway Bar Bushing Replacement
1. STABILIZER BAR WITH CONVENTIONAL BUSHING Note: Bar is loose within the bushing, decreasing the effectiveness of the bar. Also, the roll stiffness of the stabilizer bar with the conventional bushing is 17.7 N/ mm.
2. STABILIZER BAR WITH GRIPPY FLAT BUSHING Note: Flat surfaces on bar and bushing to create grip. Causes stress concentrations.
3. STABILIZER BAR WITH UPSET RING
4. STABILIZER BAR WITH CHEMICALLY BONDED BUSHING
5. STABILIZER BAR WITH COMPRESSIVELY BONDED BUSHING

Take your pick. Which one is it? The installation instructions from both MOOG and Mopar, for the Vans' sway bar bushings, say "install dry, no lubricant", time after time. The Parts guys at Mopar are vocal about that, no ifs, ands, or buts.

By the process of elimination:

• no chemical adhesive involved, scratch #4
• no upset ring, scratch #3
• no grippy flat surface, scratch #2
• no lubrication required, scratch #1

Click to expand...

It’s easy to say I’m wrong without disproving my logic. Based on your conclusions that the bar isn’t supposed to move, you still seem to think it’s a torsion bar that is supposed to be keyed/ locked to the chassis, and you couldn’t be more wrong. As if the engineers would try to counteract the weight of the whole vehicle with a smooth round bar in a round bushing clamped in a bracket with 1 bolt…
It literally does nothing, and moves with the suspension, until the suspension load changes unequally side to side, in which case it increases the spring rate of the more loaded side by leveraging against the less loaded side. The bar twisting in its bushings on the chassis is necessary to follow suspension travel. The only fixed position is the attachments essentially to the struts, which only act upon each other through a spring steel sway bar,

marvinstockman said:

Jeepman, half man-half Jeep, what you are saying is perfectly true, except, for whatever reason, the compression bonding doesn't work on these vans. A workaround is to let them slip, with very little penalty in terms of handling. My 2003 handled well when the bushings were compression bonded, and handled well when the bushings were slipping. As such, I kind of think the bushings are a non-issue, other than to resist up/down and fwd/backward motion of the bar.

Look at the bushing, and compare them to the two struts and the two strut springs. Remember, the twist/torsion of the sway bar is converted to up/down motion by the end links, which is resisted by the springs and both damped and resisted by the struts.

Click to expand...

Interesting, thanks. You are right, the compression bonding fails, or at least fails enough to cause noise. The very similar shaped sway bar bushing worked well on the 3dr Generation, I think. The problem seems to be solely with the 4th Generation, perhaps changes in overall suspension design made the sway bar assembly design marginal.

No, the sway bar being bonded to the bushing helps lessen NVH whereas a freewheeling polyurethane bushing increases it. Within the sway bar assembly itself, that decrease in NVH is significant apparently. Keep in mind that your bushings are likely restrained/bonded somewhat even though they were slipping. Most times I have taken off bushings, part of the insert will be stuck to the bar, so there is some remedial bonding.

I was reading about a Volvo that has the bushing bonded to the sway bar. The advice from Volvo and Mitchell is that when the chemical bond breaks, for whatever reason, the sway bar should be replaced. Maybe that's fair advice for the Chrysler system as well, including brackets and end links, i.e. total replacement.

Control arm bushings, trailing arm bushings and such have rubber bushings bonded to their encasements, chemically I assume, and seem to work just fine with the rubber twisting back and forth for years on end. They may even have a couple holes in them to provide some source of stress relief.. Polyurethane replacements act completely different, come in two pieces (easier to replace), and have a lubricant included. Eventually they will squeak, requiring maintenance.

All bushings on my Jeep are original. The suspension is original except for sway bar links, front and rear. The suspension has a lot of travel in it too, the front sway bar bushings are mounted up front, outside on the frame, just behind the front bumper. The OE rear sway bar links were junk, their Mopar replacement links were junk. A Jeep offr-oad Shop said I can fix that, and he did. Thousands of miles later and still good. The links up front are better but even with a Zerk on one end, have to be replaced every 5 years or so. So, Chrysler's design for the sway bar bushings on the 4th Generation gets an F at best. The Jeep gets an A. They are both compression bonded. Go figure. It isn't as simple as it seems.

PS: Did Carbuff2 use gorilla glue between his sway bar and bushing, or what? He likely has a patent pending on his fix.

Metalguy22 said:

A knowledgeable parts guy recommended a different brand black rubber that is wider and more importantly a larger Outside diameter that will in theory grip better. That's my next try. I also got the Moogs with the white nylon insert. The instructions specifically say, "Do not apply lubricant to sway bar or bushings". I don't know what Moog had in mind but generally nylon is intended to be a self lubricating bushing intended to let things rotate. If they clunk I'll try lubing them and see what happens.

In short everyone seems to get this problem and most every fix tried works in the short term and none work in the long term. I'm just going to mess with it till I get something that last a year (ten thousand miles for me) and just keep replacing them. It's great to be retired with time on my hands.

Click to expand...

Yeah, it's a full time job.

The larger bushing mentioned, is likely the MOOG that you have.

I think Chrysler gave up on trying to get the bushing tight enough with a one bolt and tab clamp system to resist the higher occasional stresses on the system (overload), that may cause some movement and some wear on the rubber. I believe the insert to be a sacrificial wear surface as and when needed, something like delrin. I think the grip is not uniform all the way around, causing the slit to open and close (clicking) and eventually wear (clunking). Sometimes, when a wheel is jacked up, the slit opens up a lot, indicating unequal clamping forces/bond breaking.

New brackets with the bushings is advisable.

Maybe Carbuff2 will disclose the full details of his patent pending solution.