eohrnberger

Glad you got it sorted. I had already replaced by CVs with brand new ones, and still had the stutter / shudder.

I guess it could come from a bunch of different things.

dmcampbell

Yes it can. Have you filled the trans mount with polyurethane, or otherwise replaced it? Mike

eohrnberger

I have not. I have the stock trans mounts that came with it. But since I replaced the spring plate bushings, I've not had the stutter / shudder.

As I've said before, lots of stuff got changed during that built, and it could have been one of any of them.

Der Treiber

Same issue on my 90S2. I had been blaming it on the synchro rings, since I have a couple of other minor transaxle issues. Both rear axles are brand new, though. If I double clutch, so as to rev match, it shifts just fine.

eohrnberger: apologies for the clueless question, but what exactly do you mean by spring plate bushings?

eohrnberger

At the end of the torsion bar, there is a suspension side of the mounting to the swing arm blades. Between the torsion bar and these blades there is a really large rubber bushing, one per side. In cars our ages, that rubber is old, soft and deforms easily, and may lead to downshift clutch re-engagement shudder. Some say yes, and other say no. What I do know is when I replaced these large, worn, soft rubber bushings with polygraphite, the shuddering went away.

Your mileage may vary.

Der Treiber

Gotcha; thx for the detail. Something along these lines, then.

http://garage.ideola.com/images/hi-res/PFR57-223.jpg

Sandman00747

Well, it looks as if it's been a little over a year since anyone has posted any new info on the s2 downshift from 3rd to 2nd shuttering problems. When I first bought my 1990 s2 with 85K it absolutely did not do this. The clutch is spring centered and only has at most 5k on it and worked flawlessly when I first bought the car. I have tried several Porsche mechanics and even had the transmission and motor mounts replaced. All to no avail! The last mechanic noticed I had new tires and wheels and asked if those were different sized wheels. I said yes I now had 17 inch wheels on the car. He thought that although a long shot maybe it was related to a bigger wheel being installed. I don't think this has any merit whatsoever, but I'm wondering what anyone else thinks or if anyone has any new info at all on this problem. It's such a wonderful car outside of this problem, but I'm determined to find it! I took the car up to ridiculous speeds to achieve similar RPM's and cannot reproduce the problem downshifting from 5th to 4th or 4th to 3rd. It's only from 3rd to 2nd. This problem borders on the bizarre to me! I would appreciate any new info or help with this problem. And, eohrnberger, I appreciate your info on the spring plate bushings, but all mechanics I have talked with said if this were a problem it would happen in several downshifts, not just from 3rd to 2nd and said my bushings were in great shape for their age! Thanks for all your past help and hints guys(this board is fantastic) and I'm hoping somewhere someone has sorted this bizarre problem out!

Eric_Oz_S2

I would say it is your clutch. Had a similar problem once, new clutch fixed it.

Sandman00747

Thanks EricOzS2! May I ask when you had this problem was it only downshifting from 3rd to 2nd gear? This is the only time it happens. And, it can being moving at a decent moving speed say 30 mph or I can also let the car coast down a hill at as little as 15 mph and disengage the clutch and already be in 2nd gear, then let the clutch back out and it will still shudder. It will not happen in any other downshifts nor on start off or any other time. Just 2nd gear. And, as I said it doesn't have to be a downshift, I can be in 2nd and disengage the clutch , then re-engage it and it will shutter. Does this still sound like a clutch problem to you? Thanks for all your help and input!

944hal

Interesting thread. I have the same issue with an 89 S2. I recently replaced the all the clutch components when the old clutch disk rubber center fell apart. The old clutch did not shudder on downshift, but the new one does. I was using the original 16" wheels, and just recently switched to 18". It only does it on the 3rd to 2nd downshift, especially at slow speed if I don't match engine revs. I also get some shudder on take off. There has got to be an answer if so many folks are having this problem. Question, anyone having this issue with a rubber center clutch disk? If you mentioned it, I missed it.

Sandman00747

944Hal, Did you change over to the 18" wheels at the same time you installed a spring -centered clutch? I am just curious as my problem did develop very shortly after I went to bigger wheels. I know this is probably coincidence but it sure is curious! I don't recall seeing anyone on any thread that has the shuttering with the rubber-centered clutch(though probably not many rubber-centered clutches left) so that makes me wonder about that issue too! And could that many transaxesl or CV joints be shooting craps and producing exact same symptom? I just don't know. All I do know is I want to fix this and I don't have unlimited bucks or time to throw at the car. There must be an answer to such a common problem and I can't believe it's 10 different problems causing the exact same symptom!

Eric_Oz_S2

Yes 3rd to 2nd only. However I also had this problem once with torque tube bearing failure - similar symptoms.

944hal

Sandman00747. It shuddered with the 16" wheels and still does it with the 18" wheels. My clutch job was done correctly. All new components and resurfaced flywheel, new slave cylinder. I really can't believe the transaxle is the problem since it didn't do it before. Just as a side note, when I put a new clutch in my race car, it's a 951, not an S2, I had shudder on take off in first gear. However, it does not do it at all on any downshift. Also, like you, I only get it in 2nd gear. I can put it in neutral, slow down, put it in 2nd gear, and when I let out the clutch it shudders. Drive me nuts!

eohrnberger

I wonder if it's aged trans-axle mounts. If the wheels are driving the engine on clutch engagement, and the clutch engages, wouldn't that cause a torque build up at the trans-axle end?

Anyway, since I've gotten better at rev matching, it's pretty much gone, and / or much less of a problem.

Sandman00747

Interesting responses guys! Hal944, so on both your '89 S2 and your 951 you have replaced the rubber centered clutches. Did you buy the '89S2 with the spring-centered clutch already installed or did you have it done after purchase and if so do you remember any 3rd to 2nd shudder before you replaced the rubber-centered clutch with the spring-centered? I am now wondering if the spring-centered clutch may be at the root of this problem. It sure seems to (following many threads on many forums) often occur with or after the spring-centered clutch replacement, or again, it may be a coincidence! I wonder if it has something to do with the "grab" on the spring-centered clutch? My clutch has only about 5K on it and the car did not do this when I first bought it! One thing all mechanics I talked with agreed on was that the 3rd to 2nd downshift puts the most torque and tension on the drivetrain in general. But like you Hal944, I can be all but coasting down a hill slowly and be in neutral and put it in second and it will shudder if not rev matched and like you it drives me nuts! Any thoughts on this anyone?