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I've been advised that the "rear trailing arms" on my 06 S Cab needs to be replaced to address "clunking" they're hearing (as am I), and after an extensive inspection (road and shop). My local dealer (I toggle between an indy and a dealer I have a good relationship with and has treated me very fairly and well, unlike many of its peers) is quoting ~$1,000 for the repair.
Ignorant questions: does that seem reasonable and what's the part itself (bushings?)? I'm going to discuss with them further but always like having some additional knowledge to better understand the repair, needs etc. and appreciate anyone's thoughts. Here's the written description:
Trailing Arm: Suspension noise is coming from rear suspension. Need to start with rear trailing arms and new hardware.
Item Description: The trailing arm is part of the automobile’s suspension. It is usually located in front of the rear axle and connects the axle to the car’s chassis. It is a relatively large piece of the suspension that supports the coil springs. When driving down a bumpy road, the trailing arm moves up and down to smooth out the ride.
Reason: A worn out or broken trailing arm will greatly hinder the performance of the vehicle's suspension.
In the process of inspecting your vehicle for safety and reliability, your technician made the following observations and recommends that you do the necessary repairs to resolve these issues.
I've done lots of recent work on the suspension, including new struts all around, mounts and tie rods. Asked about the control arms and was told they look good.
I've never heard any part of the 997's rear suspension be called a "trailing arm."
There is a lower control arm which is the MAIN arm back there. It has a ball joint at the hub end and a rubber bushing at the inner chassis end. Then you have your toe-link arms which are behind those, and it has a ball joint on the hub end as well, and a rubber bushing at the chassis end. That link is what is used to adjust the rear toe. Then you have two upper control arms, also referred to as "dog bones". Then there is the lateral control arm which goes forward from the control arm to the chassis and it has a large spherical monoball type bushing inside it undernear a big rubber boot.
MOST people don't replace just the bushings because they can be a pain to remove and replace, and usually buying a new arm that comes with new bushings comes out cheaper or similar when you factor in the labor required to R&R the bushings. Also, a lot of times you can't buy just the bushings (unless you go aftermarket)... sometimes Porsche doesn't sell them.
A new lateral control arm is about $260 new from Porsche. It's about a 5 minute job to replace it if the car is already on the lift (literally just two bolts). Then you'd probably want to re-align the car so factor that in too.
The dog bones are $150 each (there are two on each side of the car) and are a 5 minute job.
Lower control arm is like $400 and is a bit more involved to replace. I'd say it's a 30-ish minute job.
And the toe link arm is $188 and about a 15 minute job.
Prices above are EACH side, labor is each side too.
The labor estimates above are what it would take me to do it.... shops will use book rate so you would probably double the estimates above and double them again if replacing both sides.
A lot of times, suspension noises are misdiagnosed. I would want to be sure the shop used chassis ears to pinpoint the clunking unless it is so bad they can just tell from a visual with manual prying, which would mean it would have to be pretty bad.
The rear upper strut mounts can create clunking too. And I think Bruce In Philly had some rear clunking recently from a worn bushing in the rear - in his case it was a bushing in the wheel hub that the lower shock bolt goes through: https://rennlist.com/forums/997-foru...ed-advice.html
Last edited by Hindsight2010; 10-08-2020 at 05:14 PM.
If you just had recent suspension work done and the shop didn't notice control arm wear, seems like that's not the issue. Rear strut top mount gets my money for the cause of a clunking noise.
These pictures might help explain what Hindsight was describing, though your OEM components would look different than these, but similar. The large lowest piece with the big RSS logo on it is the Lower Control Arm. The other long, skinny pieces are the dog bones and toe link arms. Where you see solid bushings in mine, the OEM arms have rubber bushings there instead and that's the area that wears and causes slop or movement.
Worn or bent drop links is another possible source for a clunk sound. These are the pieces that connect the sway bars to the strut mount assembly. Mine are adjustable - yours would just be 2 cup ends with a straight metal piece connecting them. A big pothole impact will usually bend the OEM drop links.
Until someone can give you a definitive diagnosis as to the source of the noise, I'd not be inclined to make $1,000 guesses where they "start with the LCAs and see if that fixes it". As far as costs, I can't help you as I install all this stuff myself and probably work slower than the dealer or indy, but also cheaper
@Hindsight2010 you nailed it, it amazes me the depth of knowledge of the contributors here and the willingness to spend so much time to help others out. Great write-up! OP I'd ask your shop to clearly show you where this is happening using the nomenclature hindsight used. Also, this interactive graphic from Elephant Racing might be useful in identifying the components and their names:
Many thanks for the great and detailed feedback -- this is really helpful to me and puts me in a better position to ask smarter and informed questions.
Thank you everyone for your help, I'll reply back with what they tell me.
10-08-2020 | 09:56 AM
Rear Trailing Arm Replacement?
