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YOUR RESEARCHFront end "tuning fork"
Leading reported evidence
Replace every movable suspension component except
Performed · outcome unconfirmed
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Performed · outcome unconfirmed · Original poster
I exhausted every test, replaced every movable suspension component except for the tie rods.
Leading evidence: 'Replace every movable suspension component except' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'these diagonal control arms' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check movement' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
The good news is I have replaced many front end suspension components.
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No major difference before and after, many other parts were changed and overall control feels better, but no real way to measure it.
Replace strut assemblies a little over one year ago
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Performed · outcome unconfirmed · Original poster
I mentioned before how I replaced the strut assemblies a little over one year ago.
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Suggestion · Original poster
Lastly, remove the outer tie rods from the wheel carrier, and push on the rod toward the inner tie rod and steering rack again checking for unusual popping and or movement.
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Unsuccessful attempt
I replaced my "tuning forks" or "dog bones" on the front with EPS ones a couple of years ago. I may not be as sensitive as some but I noticed no change in the ride stiffness.
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Suggestion · Original poster
Speaking from experience, I would replace the control arms (coffins) while you are replacing strut assemblies because you will have to get an alignment afterwards anyway.
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Well, I am unhappy to report that installing new tuning forks and sway bar bushes did not solve my problem.
I'm chasing the source of my front end clunk going over bumps at any speed. The tie rods appear to be good. Just replaced wheel bearings, strut assemblies, sway bar links, and main control arms. I suspect these diagonal control arms. I removed the driver side arm. The rubber is very malleable and dry. Question is how malleable is it supposed to be? Car has 73,500 miles.
So, I have a better understanding of how these work. The rubber just protects the ball joint inside. I placed the joint in my vice and applied hand pressure to the joint. It did not move axially. Do I dare say it's good?
At 73k and ~15 years it's a good bet it's shot. I'd replace. Any play in that ball joint will translate to nasty clunks in the car. BTDT. 1/32" is enough to sound terrible.
You are probably right. I should just replace them. I have since buttoned everything back up, and I went out for a test drive. I can sometimes feel the movement under my feet through the floorboard.
Just be aware that those parts are fundamentally different than the stock parts. Stock is a ball joint; those EPS parts are an elastomer bushing. So they change the effective spring rate of the car, and put stresses on things differently than the original design. Not necessarily good or bad, but something to think about before changing.
I too have a clonk from front end similar to described.
A couple of extra bits of info:
The car has to be fully warmed up and probably about 10 miles after the engine has reached temperature before the clunk will appear.
Any form of light braking causes it to disappear.
Top Mounts have been done.
Guessing then it could be the 'tuning forks'?
Thanks
Chris
A good way to test them is to lift the front of the car. Grab one of the wheels hands on 9 and 3 o'clock and check for movement. It helps to have someone hold onto the steering wheel as it moves a bit between its locked position. Next, remove the wheels. Check for torn boots or abnormal play on the outer tie rods. Lastly, remove the outer tie rods from the wheel carrier, and push on the rod toward the inner tie rod and steering rack again checking for unusual popping and or movement.
986 Boxsters run that same arm in the front and they seemed to be hard to find but 997 331 043 01 is a match and what I'm running in the front. Both TRW and Meyle make this one.
I am using these in the rear and they seem to work well. No major difference before and after, many other parts were changed and overall control feels better, but no real way to measure it.
I put those on all four corners of an otherwise stock suspension a while back. Only noticeable difference was the absence of the hideous low-speed clacking at low speed. I suppose if you had the time and energy to spare, you might even pull off a DIY using parts form somewhere like this if the right sizes were available.
https://www.energysuspensionparts.co...e-bushings.asp
Cool link! That would be an interesting experiment.
I ordered new tuning forks from Pelican. I should be able to install next weekend. I will report the results (hopefully positive!)
What's the removal/install procedure for the tuning forks?
My 996 is in the air waiting for my coilovers to arrive and since I've been experiencing a front end clunk (my upper strut mounts are shot...which will be replaced with the coilovers) I may want to take this time to change these too.
Mike
Speaking from experience, I would replace the control arms (coffins) while you are replacing strut assemblies because you will have to get an alignment afterwards anyway. See if that alone takes care of the clunking. The diagonal arms (tuning forks) are easy to replace and no realignment is required.
That's a wise suggestion. What is everyone's thoughts regarding which control arms to purchase? Obviously OEM is good but, are there any non-OEM replacements that are recommended?
Mike
The first statement is true, you can change these in about 5 minutes each on the front and maybe 20 minutes each on the back, just because the front bolt is a bitch to get to.
The 2nd statement IS NOT TRUE!! Alignment is absolutely required after changing the diagonal arms. Any variation in length will directly rotate the coffin control arm and thus screw up your toe measurement. Trust me, I've seen it. I replaced mine and it altered the toe by a quarter inch, and steering wheel was not straight after. Definitely required a new alignment.
Good luck!
Interesting info about varying length. But, this causes me concern because one would think that a $125 replacement arm should be manufactured to exact specs, especially if it's a factory supplier.
Even if it's manufactured perfectly, there's a little bit of slop in the bolt holes, so you could assemble and torque it down slightly differently. The geometry is pretty easy to figure out; I don't have one handy to measure, but I'm guessing the distance from the control arm's inner mount to the bushing the diagonal arm attaches to is something like 10". So if you have maybe 1/16" of slop in that bolt hole, or in tolerances in the length of the control arm, you create a triangle with a length of ~10" and a height of ~1/16", so the possible toe angle variation there is just the inverse sine or inverse tan (doesn't matter which for this small of an angle) of .0625"/10". That's like 1/3 of a degree; too much to ignore.
It's a little more complicated than that because the tie rod also holds the knuckle, so it's not all going to pivot perfectly about the inside end of the control arm; it's a 3D geometry problem. But bottom line is if you take all this stuff apart and put it back together, the tolerances involved are potentially more than the acceptable alignment spec range, so you gotta check it. If you replace the coffin arms you can see even more variation, since the rubber bushings can wear and deflect a lot, so a new one DEFINITELY won't sit in the same static position as a worn one, even if you carefully mark and get all the metal-to-metal connections back in exactly the same spot they were before.
I've been happy with Meyle parts. Low low price and seem identical to OE. My only beef was on the diagonal arms the casting shape was slightly different so I had to modify my brake scoops slightly to fit. Not a big deal.
How did the casting vary from OE. Was it machined, or the actual cast from mold.
That would surely make me think twice, if in fact the cast was different.
The strength and stress points are designed for a reason.
I am sure glad you mentioned this.
I received the new arms. I have not installed them yet, but the first thing I noticed about them is how much stiffer the ball joints (or whatever you want to call them) are compared to the old ones. I can't move them using my strength. This alone tells me that the old ones are not fully efficient at doing the job of keeping those control arms and struts steady.
Well, I am unhappy to report that installing new tuning forks and sway bar bushes did not solve my problem. The only items I have not replaced involve the steering mechanism.
There is one detail I forgot to mention. Earlier in this thread, a concern was mentioned about how replacing the tuning forks could alter the toe alignment. I have driven the car about 25 miles since replacing the forks, and the front end feels more planted than before. The car tracks straight for sure. Maybe I got lucky. Take my experience for what it is worth.
I replaced my "tuning forks" or "dog bones" on the front with EPS ones a couple of years ago. I may not be as sensitive as some but I noticed no change in the ride stiffness. The clunk went away and is still gone. The symptoms were just as CLWICKERS described above.
I did a realignment after installation but there was no change in the readings between before and after. It still seems like a good plan.
That is good information. Thanks.
The next thing on my list is do a thorough check on the inner and outer tie rods. If those look good...
Just a thought: could the Bilstein shock be slightly less diameter than stock? Perhaps 63 ft lbs. is not enough to secure the sway bar link to the shock tube clamp.
Wow, I can't believe what the cause of the clunk ended up being. I mentioned before how I replaced the strut assemblies a little over one year ago. That included the strut mounts. Guess what the culprit ended being. Yep, one of the strut mounts left side. I exhausted every test, replaced every movable suspension component except for the tie rods. I even had the right side strut off because I had to repair a broken mount stud that I over torqued. Today, I happened to point my flash light on the under side of the left strut, and I noticed wear and disfiguration. Then, I wedged a pry tool to test unusual movement at the shock tower. Sure enough, the rubber was mush. The mount is shot. So, how the heck does a part only last 3500 miles? In any case, I ordered a new one. At least I can put this issue to rest.
To be honest it was really just a shot in the dark suggestion. When u had origiinal posted there were 2 or 3 other top mount failures that just happened and it seemed the same symptoms. I too would not have expected it to be the problem since u just replaced them but its a good lesson to learn. Never rule out anything even a newish part.
So true. In my mind there was no way a new part would fail. Like you said, "Never rule out anything." My experience is a testament to that.
Thank you all for your help and input. Rennlist has a great 996 community👍
Guess I never answered this question. The I-beam section of the Meyle diagonal tuning fork arm was just slightly beefier towards the ends; it begins to flare out sooner to widen out to the ball forward ball joint, so I had to trim the brake scoops slightly so they would wrap around the arm cleanly. The OE Porsche arms were just a tiny bit more spindly. We're talking small fractions of an inch here.
