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Old 05-20-2019, 05:57 AM   #1
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Thunking / knocking noise coming from rear when going over bumps

Without taking it to a garage and crying gently to myself because of costs,

will try to get a video of it. but its def not engine related. can hear it only at slow speeds.
does anyone know what it possibly could be and if it is at all possible to diagnose myself by getting under the car and moving things around? ? i've just bought myself some car ramps.
i have been told it could be the trailing arm, or the ARB... but could be a couple of other things.

sorry, i'm a bit of a n00b when it comes to cars to be honest. but i'm ready and willing to learn... obviously if its a hard part to replace i'll get it done by a proper mechanic if it needs to be done urgently.
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Old 05-20-2019, 06:13 AM   #2
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From the description you gave, it's likely the rear trailing arms, which although not fun to replace, are easy enough. You can do it with the car on ramps.

How many miles on the car?
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Old 05-20-2019, 06:33 AM   #3
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From the description you gave, it's likely the rear trailing arms, which although not fun to replace, are easy enough. You can do it with the car on ramps.

How many miles on the car?
the parts arent bad, about 150 each. Ive replaced mine on all my cars around 80K. trying to move them around doens't tell the story, everything looks fine but it isnt.
they are a challenge to replace unless you have a huge breaker bar, really helps to have the car on a lift. On ramps you have a tough time getting leverage and you cant swing the tool through the arc. You will need an alignment after as well.
I found it best to have a shop so this, but that's a personal decision.
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Old 05-20-2019, 06:57 AM   #4
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ok, thanks. its about 90k miles on the clock.
so if it is these (and sounds like not an easy way to verify?? would a garage be able to test better? or is it hit/miss for them too?)
i've just looked at what they are and I can't see how they would 'wear' to need replacing as they are just a metal rod. will it have snapped or something? i see some ones from a breakers for £17 or new ones. or https://www.ebay.co.uk/itm/PORSCHE-BOXSTER-CAYMAN-911-REAR-TIE-ROD-TRAILING-ARM-MEYLE-A1321/202297117092?fits=Plat_Gen%3A986&epid=249039273&hash=item2f19d909a4:g:mCMAAOSwER1a3dcf&frcectupt=true#rwid for £55. i assume i'd only need to replace 1 (although both could be a good idea i guess)
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Old 05-20-2019, 07:38 AM   #5
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ok, thanks. its about 90k miles on the clock.
so if it is these (and sounds like not an easy way to verify?? would a garage be able to test better? or is it hit/miss for them too?)
i've just looked at what they are and I can't see how they would 'wear' to need replacing as they are just a metal rod. will it have snapped or something? i see some ones from a breakers for £17 or new ones. or https://www.ebay.co.uk/itm/PORSCHE-BOXSTER-CAYMAN-911-REAR-TIE-ROD-TRAILING-ARM-MEYLE-A1321/202297117092?fits=Plat_Gen%3A986&epid=249039273&hash=item2f19d909a4:g:mCMAAOSwER1a3dcf&frcectupt=true#rwid for £55. i assume i'd only need to replace 1 (although both could be a good idea i guess)
thats not it...in the exploded diagram from the link you just provided...its part number 8. This is the most likely cause.
Nothing is broken, but the rubber ends get hard and shrink...just a little and the clunking noise shows up. almost impossible to check because everything is under tension. even after removing the part I couldn't tell something was wrong.
some after market stuff is out there for about 150 bucks, some fancy ones are out there for racers as well. I use the TRW replacement part and have been pleased since I replaced them 2.5 years ago on the first car. Just changed out the 2002. solved my problem. replace them both.
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Old 05-20-2019, 08:10 AM   #6
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thats not it...in the exploded diagram from the link you just provided...its part number 8. This is the most likely cause.
Nothing is broken, but the rubber ends get hard and shrink...just a little and the clunking noise shows up. almost impossible to check because everything is under tension. even after removing the part I couldn't tell something was wrong.
some after market stuff is out there for about 150 bucks, some fancy ones are out there for racers as well. I use the TRW replacement part and have been pleased since I replaced them 2.5 years ago on the first car. Just changed out the 2002. solved my problem. replace them both.
Tony... couldn't just the rubber (bushings) be replaced... or does the metal get distorted (necessitating complete replacement)?

Should they be replaced in pairs?

Thanks!
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Old 05-20-2019, 10:13 AM   #7
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The way to test whether its the trailing arms is to find a bump or a hole that creates the knock. Try driving over it while either accelerating or braking while the rear end is going over it. If you don't get a knock its one or two trailing arms.
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Old 05-20-2019, 10:36 AM   #8
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Tony... couldn't just the rubber (bushings) be replaced... or does the metal get distorted (necessitating complete replacement)?

Should they be replaced in pairs?

Thanks!
unless they are specialized "racing" trailing arms, the rubber isn't replaceable. replace em both...anything short of that is false economy
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Old 05-20-2019, 01:45 PM   #9
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The way to test whether its the trailing arms is to find a bump or a hole that creates the knock. Try driving over it while either accelerating or braking while the rear end is going over it. If you don't get a knock its one or two trailing arms.
ok i'll try that tomorrow.. so if the trailing arms are playing up you shouldn't hear the clunking noises whilst accelerating/braking?
if it does still make a noise, what could it be? what could i check from underneath to confirm?
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Old 05-20-2019, 04:10 PM   #10
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unless they are specialized "racing" trailing arms, the rubber isn't replaceable. replace em both...anything short of that is false economy
Thanks!










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Old 05-20-2019, 04:37 PM   #11
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Sorry to give you the bad news, you can screw around all you want trying other things, but it's the trailing arms. They wear out at about 80K. You can look at them and not see anything wrong, but the plastic bushing wears enough that when there is a lot of load put on them, like going over a bump, they'll make a knocking or banging noise.

In my case, they were making enough noise that it was difficult to have a conversation in the car. But after replacing them, then I could hear all the other suspension parts that were shot, and I ended up replacing everything else. My car had 145K on it, though.

I was able to replace them on ramps, but it's really tight. I used a long enough extension and a long breaker bar to get them loose, and then made sure they had the correct torque when tightening them. If you don't correctly torque them, they'll make noise because they aren't tight enough. I didn't get an alignment, and the car drove fine.

The rear trailing arms seem to be the first thing in the suspension that wears out, so you have a lot more parts to look forward to replacing in the near future. Welcome to Porsche ownership!
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Old 05-20-2019, 05:54 PM   #12
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Read this part again....it will cost BUT, hands down the best car I have owned and I have owned a few, currently have 6. Repairs seem to come in waves. Good luck









The rear trailing arms seem to be the first thing in the suspension that wears out, so you have a lot more parts to look forward to replacing in the near future. Welcome to Porsche ownership![/QUOTE]
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Old 05-20-2019, 06:03 PM   #13
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Has anyone tried these? They're $378 for 2.

https://www.youtube.com/watch?time_continue=11&v=O57sPjCW7YQ

I'm not sold on them because it looks like the motion is severely restricted.

Bushings like that should lay horizontal for up/down motion and vertical for left/right motion. These are mounted vertical on an arm that travels up and down. I'm thinking early failure.

There's a reason the Porsche engineers spec'd ball bushings, right?

Any thoughts?
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Old 05-20-2019, 06:33 PM   #14
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Pay the money if you think youíll have the car for another 10 years or racing. The trw links are selling out there for 75 bucks, I paid 150 for them. They fixed my problem and donít think Iíll need to replace them again. Do the math but like to see the innovation, especially on 20 year old cars. We are keeping history alive and having fun in the process. Thoughts?


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Old 05-21-2019, 12:47 AM   #15
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ok thanks all, i'll prob end up taking it to a garage anyway to have a look.
out of interest, other than the annoyance of the noise and it probably getting worse if not replaced, is it something that is dangerous if not replaced?

Also to give a bit of context, I bought the car a couple of weeks ago. Did a test drive, no issues whatsoever. drove on some bumpy roads. bought the car, drove 10 miles, filled up with fuel. and thats when i started hearing the noise. I originally thought it was relating to the weight of the fuel , but it makes the noises all the time now regardless of empty tank or not.
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Old 05-21-2019, 03:12 AM   #16
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Pay the money if you think youíll have the car for another 10 years or racing. The trw links are selling out there for 75 bucks, I paid 150 for them. They fixed my problem and donít think Iíll need to replace them again. Do the math but like to see the innovation, especially on 20 year old cars. We are keeping history alive and having fun in the process. Thoughts?


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Where did you find TRW for $75?
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Old 05-21-2019, 05:19 AM   #17
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ok i'll try that tomorrow.. so if the trailing arms are playing up you shouldn't hear the clunking noises whilst accelerating/braking?
if it does still make a noise, what could it be? what could i check from underneath to confirm?
It could be drop links, and almost any other bushing in the suspension. The test I outlined work well because the trailing arms' function is to provent rearward and forward motion of the suspension.

I don't know whether this is always true, but when mine started making noise they were quiet when cold, but as they heated up they would get noisier.

Good luck!
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Old 05-21-2019, 06:51 AM   #18
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Agree with above. Most likely trailing arms. I thought it was pretty easy to do with a jack and 2 jack stands, but higher / roomier is always better for work. I remember one side was difficult to access with the torque wrench b/c other hardware was in the way, I think I used a really long extension to do that chassis bolt.
Went with the Vertex polyurethane rebuilds and have no complaints over 3 or so yrs of use. Replaced the pair just because the poly bushing is a design change and I wanted to stay symmetric. If I had to do it over, might go back to conventional style just for theoretical reasons. Would probably use the 987 version, which reportedly fits perfectly.
BOL.
BTW Not a safety issue, but who knows if all that rattling around accelerates wear on other suspension components. Certainly wears on your pleasure of driving.
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Old 05-21-2019, 07:15 AM   #19
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Where did you find TRW for $75?
apologies, I found the Meyle for 75 bucks, but shipping is 40 because the supplier is in Europe...I went with TRW both times, last purchase was fcp euro because of free shipping.
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Old 05-21-2019, 07:41 AM   #20
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apologies, I found the Meyle for 75 bucks, but shipping is 40 because the supplier is in Europe...I went with TRW both times, last purchase was fcp euro because of free shipping.
Thanks.
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