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Discussion Starter · #1 ·
Hey guys, I feel like I'm losing my mind a bit. A few months ago I installed Numeric cables and conducted an oil change on my six-speed 987.2 2.9. Since completing that job, the in-cabin valvetrain noise has been quite aggravating. It sounds like I'm driving a diesel around while inside the car. Outside, the motor doesn't seem louder than it did before.

More concerning is a subtle, but certainly noticeable, rattle that's audible under light throttle between 2500 and 3500 RPM. It is hard to replicate out of gear, but it is easily replicated while driving on the highway. The rattle is not consistent with RPMs.

I understand that Numerics increase cabin noise. I have read every thread I can find on people's experience post install, however nobody seems to complain about loud valvetrain noise. As a side note, when installing the cables, I reused the factory insulation and grommet. In a further attempt to solve the issue, I rechecked the cut grommet and then dynomatted key areas against the firewall and under the center console. The sound is reduced somewhat, but still quite obvious.

Regarding the rattling noise specifically, I'm not convinced that it's normal. With the foam/carpet that sits above the engine cover removed, the noise is even louder and more pronounced. I find the sudden increase in valvetrain noise somewhat concerning as well.

The car has around 60K on it. This was my first oil change (was purchased a year prior) and I used an OEM filter and Mobile 1 0-40. I had some drain bolt shenanigans during the change (which I did the day before I had to head out of town for a week) and ended up having to leave the car while it slowly drained six quarts of fresh oil through a cracked drain plug. When I returned, I extracted the broken plug and refilled with another seven or so quarts of 0-40 after installing a new plug. The car also received a new water pump about 10 months ago.

I'm not quite sure how to approach this. Am I being paranoid? Is the sudden increase in valvetrain noise normal for steel shift cables? Is the rattle, as I've described it, common? My only point of reference is a 997.2, and that car has stock cables and is significantly quieter inside the car. I've scoured the forums and can't really find anything helpful. I do all of my own work on my cars, and the only mechanic I trust is a well-regarded race shop with a long wait time.

Any ideas or help would be greatly appreciated.
 

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I was expecting a significant amount of increased NVH in the cockpit after installing the Numeric cables and short shifter. Not every post mentioned it, but many did. Keep in mind that the posts were for 997, 987 Boxster and 987 Cayman.
Mine happened to be a 987.1 Boxster but with the 5-speed rather than the 6-speed.

I was pleasantly surprised to get very little additional noise or vibrations. I DO hear a more metallic sound during the shift itself, but nothing that doesn't match the direct-link feel of the linkage itself.

So although you are probably a 6-speed and thus have the cables crisscrossing the top of the motor and then snaking down both sides, I still can't think of a reason the cables would have caused the noises you describe.

Sent from my SM-G988U using Tapatalk
 

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Discussion Starter · #3 ·
Many of the threads I've read reflect your experience. My initial thought was that sounds was creeping past the rubber firewall grommet, but it still persists after double checking. I wasn't aware however that five- and six-speed cars have the cables routed differently.
 

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Yes, a 5-speed has both transmission shafts on the passenger side of the tranny, AND it doesn't require the stiff angle-bend of the one cable that the 6-speed has that scenario. I don't even think the 5-speed has the reputation of the cables breaking and stranding the car.
However, it does suffer from the same plastic induced vagueness of the oem shifter hardware, especially as it ages.

Did you wrap the new cables in the isolation rubber sleave material? I can imagine without that sleave the Numeric cables WOULD transmit a considerable amount of engine compartment noise and vibration. They are pretty stiff.

Sent from my SM-G988U using Tapatalk
 

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Discussion Starter · #5 ·
I, regrettably, didn't purchase silicone sleeves. I did reuse the insulation that's on the factory cables. I'm not 100% convinced the noise increase is related to the cables, however if I can't find a solution then I may reinstall the factory cables just to troubleshoot. Ultimately I'm okay with the noise, as long as it's not indicative of a larger
mechanical problem.
 

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I'd try getting the silicone sleeves, they help a lot.

Even with the sleeves and a bunch of dynamat the Numeric cables let in some unpleasant sounding noises in my experience. They're not too loud but if you're paranoid they're of the "oh crap my engine's going to explode" variety. It's been like four years, though, so I don't think my engine's going to explode.
 

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Are you sure it is valve train noise? Does the sound go away when you press in the clutch? My Numerics definitely increased the noise in the cabin but I only notice it with the top up and a low RPMs. The noise goes away with the clutch depressed.
 

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I had no additional engine noise after my Numeric install even though I had sliced the factory grommet to accept the larger cables. It only takes a very small hole to transmit a lot of noise - I'd suggest shining a bright light on the engine side of the grommet and see if there is anything visible from the cabin side of the grommet. I'd try sealing with something as simple as silicone for a start. My cables were encased in fuel hose by the prior owner so I left it that way. They definitely do rub against the engine cover a little but that is same as stock.
 

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Had my cables replaced by a very competent local Porsche specialist when my 5 speed car needed a clutch 20k miles ago. The cables broke during disassembly so it wasn't a bad idea. They recommended the Porsche ones but they were not available at the time. The Numeric left a lot of gear noise that sounded similar to the interior of a cup car even though the shop did reuse the original grommet. Dynamat on both engine covers and inside the console helped as well as covering the cables with 3/8" ID tubing but still not OEM quiet. It has seemed to settle in somewhat when I added a function first shift kit which is a nice update but also expensive. Having added a Top Gear valved exhaust may also be doing a lot to cover the noise as well.
 
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Discussion Starter · #10 ·
Are you sure it is valve train noise? Does the sound go away when you press in the clutch? My Numerics definitely increased the noise in the cabin but I only notice it with the top up and a low RPMs. The noise goes away with the clutch depressed.
Yes. Depressing the clutch has no affect on the noise. It's most certainly constant valvetrain noise. Hell, I hear the engine ticking away at idle while the car is neutral.
 

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I had originally only added sound insulation to the part of the cables in the engine bay. That left quite a bit of noise that was proportional to engine speed. Later, I reused small pieces of the OEM cable insulation for the parts of the cables that were in the center armrest between the shifter mechanism and the firewall. That made a noticeable improvement. Still not as quiet as original, but at least it isn't a constant reminder.
 

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For what it's worth, I also have a 987.2, 2.9L, 6-speed, that I upgraded to the Numeric shifter and cables. I was worried about getting extra cabin noise, so I purchased/installed the Numeric silicon tubing, and was very careful when cutting and preserving the rubber grommet. Just like someone else posted, I installed the silicone tubing on every inch that I possibly could, including underneath the center armrest. I was very pleasantly surprised that I did not get any additional cabin noise as a result of the Numeric shifter and cables.


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