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Old 09-30-2018, 05:02 AM   #1
FreeEMSFred
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Default Rear end clunk + wandering at high speed. 240 wagon.

Not looking for help so much as creating a place to record what I found.

For a long time the rear end of my 240 has had a clunk, however when I first noticed it I tried to find it, and failed (story of this car + me, makes me wrong every time! lol). A few weeks ago I noticed the car felt wandery like it might with 15psi in the tyres, so I checked and topped them up. No better. Drove it around all weekend at speeds up to about 140kph sustained and the wander was most obvious at higher speeds, not to the point of keeping in the lane, but nearly. No steering play felt. Today under down shift or decel to accel transition noticed clunking has gotten worse, sometimes multiple clunks per event, like a small series of them. I strongly doubt the front end has gone from beautiful alignment to toe-out by itself.

Guessing several of the bushes in the arse end are flogged and need replacing, so will endeavour to investigate after some higher priority chores are out of the way.

However any tips re the wandery nature of it or the accel/decel transition clunks (either direction) are welcome! :-)

No, didn't search, just noting the story down, for now.

Cheers.
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Old 09-30-2018, 08:49 AM   #2
Vincent Gagnon
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If it's rear suspension bushing related, and it sounds like it might be, it can't be a zillion things.

it's either (7,6,3,2,4 or 5) or a combination, or ALL OF THEM!

Just crawl under there and gawk at the bushings until you figure out if which one of these blimmin' things is buggered.

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Old 10-08-2018, 08:06 AM   #3
FreeEMSFred
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Yeah, that's the thing, when I first heard it, I did dive under and stared and wiggled and found nothing. They all looked okay, or seemed to. I'm hoping now that it's worse it'll be more obvious!

Haven't gotten back under, yet, though. Lots going on, but should have a chance in the next month or two, I hope.
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Old 10-08-2018, 02:41 PM   #4
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I'd be willing to bet it's the trailing arm bushing (#2 in the diagram above). It isn't necessarily super easy to tell that they're cacked unless you drop the trailing arm and take a peek. The torque rods (6 and 7) are the usual suspects for rear end clunkage, but they don't typically cause the car to wander. If you haven't replaced any in a while while, odds are pretty good you have more than one borked bushing.

Pro-tip: replace everything but the trailing arm bushings with polyurethane bushings. They're slightly more expensive, but they'll last waaaaaay longer than the OEM rubber ones. I put some in about 100k miles ago, and they still look brand new. Unfortunately the trailing arm bushings need to be able to twist in order to work properly, so you're kinda stuck with the rubbery stock style, unfortunately. There are spherical bearing conversions available (I have one I've been meaning to install), but they're expensive and the lead time is about a million years.
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Old 10-08-2018, 03:20 PM   #5
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Another clunk from the rear of the car is that rear ujoint. It takes a lot of abuse.

But the wandering is bushing related for the most part. Also how are the shocks? if they are worn they contribute to the problem as well.
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Old 10-09-2018, 11:51 PM   #6
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In order of typical failure...
1. Upper control arm bushings.
2. Main TAB bushings.
3. Front lower trailing arm bushings.
4. Panhard bar bushings.

If they have never been done, I would recommend you just replace them all.

Don't use poly bushings, they just bind and squeak.
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Old 10-10-2018, 08:07 AM   #7
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I'll lay down 20 greenbacks to say it's not the U-joint. Last time I made a monetary bet on a car I was a teenager and I lost Not this time.

Shocks are meh, but functional. The ones in my 740 GLE 16v are way softer and don't give any drama even doing skids all day. Contribute, yeah, but a clunk and wander both require play/gaps to be an issue.

Fjergus, I'm unwilling to bet you're right, but you probably are given your comment on hard to see - would explain my inability to spot the issue. What happens if those are urethane? Excess stress on the steel parts under bump/rebound when geometry changes?

Chances are I'll go with ozzy made superpro urethane for at least most of it - comes with a special grease and I've never had issues with urethane squeaking or binding before. There are applications where it's the wrong choice, eg front upper arms of R32 skyline where a hard precision bushing is required and urethane is too soft.

quillc, which location(s) bind and squeak for you? I have in the past had a local company custom make me urethane bushings to my spec in my chosen grade of urethane. If the trailing arms need more give as Fjergus says, then I could have that done and get them to use a soft grade. But probably not worth the hassle. Super useful for obsolete cars that you *can't* get off the shelf stuff for, though.

Chances are none have ever been done, so replacing the lot in one hit does seem like a sound approach. Best I get onto the hydraulic press project that's been shelved for months, then... :-)
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Old 10-10-2018, 11:49 AM   #8
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Quote:
Originally Posted by FreeEMSFred View Post
quillc, which location(s) bind and squeak for you? I have in the past had a local company custom make me urethane bushings to my spec in my chosen grade of urethane. If the trailing arms need more give as Fjergus says, then I could have that done and get them to use a soft grade. But probably not worth the hassle. Super useful for obsolete cars that you *can't* get off the shelf stuff for, though.

I've just used the iPD upper control arms that have the poly bushings coupled with the TAB poly bushings (Superpro I seem to recall). Pretty sure the TAB bushings were at fault. There were several times where I would go through a dip to enter a driveway of a business. Since the car is lowered, I would go at an angle and the rear right tire (turning right) would hang in space as the bushings were so stiff that the suspension wouldn't articulate. Got stuck once that way with the one wheeled wonder just spinning away in space.

I put a set of Ben's comfort upper arms and spherical TABs and the problem went away.
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Old 10-10-2018, 11:54 AM   #9
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I vote trailing arm bushings. Spherical is great there but comes at a price.
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Old 10-10-2018, 12:12 PM   #10
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Quote:
Originally Posted by JW240 View Post
I vote trailing arm bushings. Spherical is great there but comes at a price.
And road noise. I made my own bushings because I couldn't see paying what Ben wants. They are nice and solid but are more noisy ( road noise) than rubber ones. However, it did not solve my wondering problem.

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Old 10-10-2018, 12:36 PM   #11
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Originally Posted by volvo? View Post
And road noise. I made my own bushings because I couldn't see paying what Ben wants. They are nice and solid but are more noisy ( road noise) than rubber ones. However, it did not solve my wondering problem.

Jeremy
Yes. I made my own version too. With rubber in the front of the trailing arms it's quite subtle though.
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