Silk

So last week I brought my 996 C2 in for installation of an Ohlins Road & Track suspension setup. Final result is that the car got lowered approx. around 20mm in the front and 17mm in the back. All went fine. Car drives great. Firm ride with great souplesse (11 clicks in the front and 12 clicks rear)

Yesterday I noticed a grinding noise on the right side when making sharp left turns, especially under acceleration. Right turns are smooth as should be.

I did a quick search to see if I could identify myself the problem and came accross the following posts.

https://rennlist.com/forums/996-foru...d-turning.html
https://rennlist.com/forums/996-foru...hand-turn.html

Transmission mount seemed to me not the issue as I upgraded them 5000km ago. But the posts above made me suspicious about the CV joints.

And indeed, I found the evidence of at least the right CV joint in the rear being in failure mode as I found traces of the sticky joint grease on the edges of the fenders and inside the wheel well.

Probably the CV joints were already in bad condition. Lowering the car resulted in a different angle of operation of the joint. Also the change in angle also resulted in extra longitudinal forces on the joint (correct?). This was probably the final push for the joints to fail and to start grinding when turning and accelerating hard. It is most likely that the left side is also in a not so good state.

I will have to replace the whole shaft. Is there further any issue that will cause a problem for the new shaft and CV joints because the car is lowered? Any adaptations necessary to the shaft? Or should all be fine as is?

Sneaky Pete

I had done the X74 suspension on my old 996 C4. I believe I stressed / ripped the CV boots during the install on the fronts. I ended buying some very good used half shafts to correct the problem. I'm not aware of any adaptors......I'm thinking since the wheel center point and halfshaft locations are the same you don't adaptors.

alpine003

I've been running lower than you for over 5 years on my original 125k cv joints and no issues.

Is it possible that you or previous owner ran over something before to cause this? Also, what do you mean by "failure mode"? Just because it leaks grease doesn't mean the joints themselves are bad.

Have you checked to make sure nothing is touching your rotors like a stuck stone or bent brake heat shield?

Are you sure the grinding noise is in the back and not front? Steering would have nothing to do with your CV joints since you have a RWD. Could be a bad wheel bearing.

OKB

Most likely its a age problem and you dont say how many miles are on the car or year. but its 10+ yrs old.

white out

Buy some grease and new boots.

Silk

Could be possible! I can understand that he did not want te tell me when he sold it to me

Well, considering the amount of grease it spitted out and the grinding noise it is making I don't think that is normal. Could be that they are still okay and can be revised. A closer inspection by my Indy is in progress.

Yes, I went first instance to the shop that installed the new suspension. It was the first thing they verified.

Yes it is definitely coming from behind me. The grinding is also causing a vibration which I do not feel at all in the steering wheel. Steering is sharp as a knife in fact. The fact that the grinding noise is only occurring with serious cornering could also indicate a problem in the differential. Wheel bearings are also on the check list of my indy, but I don't think they are bad.


Yes, certainly that is a factor! 2002 996 Carrera with 97k miles

My indy is looking at it. He ran the car and after two corners he told me it sounds like CV joints. Also on the other side he could detect some anomality. I will know more tomorrow

JMLavoie

Silk;
I picked up on your statement: ... firm ride with souplesse. ...
I'm au fait with the word souplesse given my fr-Cdn background but relative to what?
11 and 12 clicks out of how many in total?
Ie, are you in the middle of band in order to get street driving 'souplesse', while being firm during cornering?
Very curious as I need to do something with my suspension and undecided what to do.

Silk

Not too much experience yet. Did not have the time to experiment with different settings. They go from 0 to 20 (hard to softer). The suspension was set up by an authorised Ohlins shop. They have dialed them in for me to give me (according to them) the most balanced street setting (the outcome was the 11clicks front an 12 rear). I only have driven this setting so far. So no feedback yet on a harder trackable setting.

When installing they revised the front arms with powerflex bushings because the rubbers were cracked on the left side. So both left and right were modified.

The car is really different. More stability in the curves. Much better feedback. As far as my first impressions go the suspension in this setting is noticeably firmer compared to stock but ride comfort is pretty good. I dare even to say better. So far so good. I need much more time to be able to make a more objective review. After all I went from the original shocks to brand new ones. So it is difficult to compare.

Also be aware that not every click represents a linear increase/decrease in damping characteristic. Ohlins itself indicates to use 0-2 as the hardest setting, not to go much lower. Same goes for the softer end of the range.

They told me that probably for track use I will end up with something in the range of 5-8 clicks depending upon personal preference and driving style.

The car is now on a set of yokohama ad08r (f:235/40/18 r:295/30/18) after aligning and weighing the car they were fairly impressed about the combo during test drive.

I was looking into the Bilstein b6 b8 and pss10. But I took the plunge without any prior test driving to go for something less 'common'. What was a key factor in deciding was the one-way adjustability. Not too many parameters too look after. But still flexibility to go firmer or softer without any effort.

Silk

Short update: my indy confirmed the theory of the joints being not working as should. He is going to check the clearances in both longitudinal and rotational direction for the inner and outer joints both left and right side. Further all the suspension connections will be rechecked again. This analysis will further decide if re-greasing and new boots will suffice or replacement of the joints is necessary.

I am thinking to change also the differential oil and the tiptronic transmission oil. That means I will have a clear maintenance reference point. As I changed over the last months already fluids and filters, ims, bigger water pump, low temp. thermostat, adapted cooling, x51 oil pan, modified AOS, braided stainless steel brake lines, suspension, tires. 25k miles ago the previous owner had the engine resleeved with nickies incl. a new crankshaft etc.

alpine003

Interesting. I haven't personally ever witnessed a grinding noise as you describe from CV joints. They usually click or clack. If you've seen the joint past the boots, you can see how grinding would be rare, especially only making the noise on sharp turns as you stated.

Either way hope you get it sorted out.

I don't think you'll need to do the IMS if you already got Nickies in there, unless you subscribe to the strict maintenance interval, including time.

Silk

Ok maybe grinding is not precisely the right description of the noise. It is a combination of grinding with knocking which gradually builds up and disappears depending on load. The knocking comes up with sharp accelerated cornering, especially when starting from slow speeds. This is a typical heavy load scenario for the joints. Combined with the fact that I just lowered the car a bit it is for me to much coincidence. Also that a lot of grease get out at the same time the knocking started. I am wondering how much dirt made it into the joint. Maybe the joints already worn out before due to moist, dirt etc. and the new neutral position after lowering caused it to wear out faster.

Another possibility is the shaft and joints do not have enough longitudinal clearance when it is under load. Hence causing a vibrating counter movement
It could also be the differential off course as in sharp turning the differential starts to compensate for rotation speed difference between inner and outer wheels. No idea how that would sound.

I have no time, nor the tools and detailed knowledge about how to diagnose it. I will have to rely on my indy for this. But I understand some of the mechanical aspects that are in play here. Thanks a lot for the input from all of you! Much appreciated

The IMS is already replaced with an OEM version from SKF. I know, it is not the safest option. Maybe I will change it later for an improved ceramic bearing. Right now I will let it inspect evere 15-20k miles as good as it can. I have also installed a magnetic drain plug and spin on oil filter adapter and I am changing oil 2 times per year as I am running +15k miles per year. For the rest fingers crossed.

alpine003

I really don't understand the logic to go through all the hassle and expense of getting Nickies and then just replace with a SKF OEM equivalent?

Was this the black one advertised on ebay a few months ago by chance?

Silk

Thanks for your considerations!

I did not go through the hassle of resleeving the engine. The previous owner did. But thanks again for your kind concerns.

It was replaced and I am looking to a more solid upgrade as soon as I know what. Here in Europe the IMS solutions are not so common yet. The ims failures are scarce on the forums here. We see more scored bores and related failures.

alpine003

Yeah I meant the previous owner's mindset.

Silk

Thanks for clarifying!