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Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - Printable Version

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Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-19-2012

it seems that the 968 has 2 different kind of torque tubes. one is slit like the 944S2 with a long slit running down the tube, and one isn't. so far, i have not been able to determine why porsche was not consistent, when it changed, or if they had a reason.



the 968 torque tube is specific to the 968. it is a different length, and since we have a different transmission, i assume the rear flange is also specific to our car, though i have not seen them side by side yet.



the slit is there to dampen vibrations and resonance down the tube. i get that. but why some cars and not others? if it was an S2 thing, then you would expect it to be at least in the early cars, and then maybe deleted, but it seems there are quite a few cars with the slit, and more than just the early 92s would account for, unless all of the ones with slits we've heard of have somehow coincidentally been 92s. we know of a late 92 that has a solid tube. my early 94 has a solid tube.



so, the next time you have your car up in the air, check it out. what kind do you have?

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - BeBe - 04-19-2012

Not having spent much time under the car, I don't know what I'm looking for. Be happy to look though.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - TonD - 04-19-2012

Pictures would help, I have no idea what to look for either!

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-19-2012

look above the exhaust at the torque tube. it will be a LONG slit opening running down the length of the tube



here is a shot of an S2 tube



   

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - Cloud9...68 - 04-19-2012

Flash,



I checked mine last night, and it has no seam. Mine's a 92, but I don't have the VIN number handy, so I don't know how early or late it is (I think it's a pretty late '92 - at least it doesn't have the recessed hood badge), so I won't be able to respond to the poll till I get home.



Be aware, though, that there's a heat shield that runs under most of the length of of tube, obscuring the view of where the seam would be located. Now that I see where the seam is located, I'll take a closer look to confirm.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-19-2012

i think you can still tell though by the ends. i suspect it has the added pieces at the ends like the S2 has with those "V" shaped cuts in the sleeves. mine is just a straight tube with no "sleeves" on the ends.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - tamathumper - 04-19-2012

Here's a photo of mine - it has a "sticker" on it?



[Image: torque_tube.jpg]

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-19-2012

looks like yours has a slit

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - Cloud9...68 - 04-20-2012

Flash,



So sorry, I stand corrected - mine DOES have a slit. It doesn't extend to the back of the TT, which is where I was looking from when I concluded it's slitless, but from the front, you can clearly see it. It has a "sticker" on it, just like Tama's. And I think mine is a late 92 - it's VIN ends in 820386, for those who can correlate that to the car's vintage.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - MB968 - 04-21-2012

Mine has the slit over about the first 20" just after the bell housing and the collar. My vin ends in 820164, and was delivered to the first owner on 24Feb92, so I listed it in the poll as an Early '92 model.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - Monstrous4Banger - 04-21-2012

I havent dug out the TT in my 968 yet, but if IIRC Constantine at black sea r&d said they are the same as 944, minus the slit. Some have a different number of bearings if I recall too.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-22-2012

i had to go and edit the poll, because the year selection wasn't giving me a spread, and it wouldn't let people answer one question but not the other.



tamathumper, you can probably go and delete your vote and re-vote to put yours in 93, but if you can't it's ok



so far, it looks like they changed it at the end of 93. very odd. also troubling for higher output cars, track cars, and cars with a single mass flywheel. i can explain more about that later.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - tamathumper - 04-22-2012

I thought I *did* select '93... Well, I'll go delete and re-do anyway.



EDIT: no clear way of how to do that...

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-22-2012

if the option doesn't come up, it won't let you



ring me up - i have something about this whole issue that i need to talk to you about

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - Cloud9...68 - 04-22-2012

"also troubling for higher output cars, track cars, and cars with a single mass flywheel. i can explain more about that later."



<img src="/forum/images/smilies/968/ohmy.png" class="smilie" alt="" />

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-22-2012

yup - just dropped you a line to call me

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - mbardeen - 04-22-2012

It won't let me change my vote, but mine is a 93 and it does have a slit.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-22-2012

thanks - yeah - glitch in the software. i'll record that here accordingly.



i am really trying to figure out where they changed it. the slit is a fairly serious design complication. while it reduces resonance, it also reduces the ability to retain concentricity. this presents itself as a real problem if you introduce things that will cause deflection, such as higher output engines, or repeated hard shifting, as in the case of track use, both of which would be seriously increased when in conjunction with a single mass flywheel.



a solution is in the works, but it isn't going to be cheap.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - Monstrous4Banger - 04-22-2012

This is why I have a spare one with no slit on the shelf.

Slit Skirt Jeanie isn't wearing those Slit Skirt-or is she? - flash - 04-22-2012

good call.



this is potentially a very real problem. we probably just haven't seen failures yet due solely to the small sampling of those pushing the envelope. the failure won't be immediate, and won't produce a lot of symptoms. frankly there just haven't been that many cars out there yet pushing it. of those, there is no telling how many have the slit and how many are solid, and of those, how many are running a single mass flywheel. my guess is maybe a dozen cars might have the combination, and of those maybe 1 or 2 are at or near the point of showing any signs of issue.



while we will probably see some failures fairly soon on cars with DMF units, the problem is exacerbated with the use of the single mass flywheels, and the vibrations they transmit down the shaft. the slit tube flexes as the engine torques. the slit is design to mitigate vibration and noise, but in flexing allows the bearing to move, and the vibrations generated from the single mass flywheels then cause it to walk.



i had a solid tube and still walked the bearing, due entirely to the single mass flywheel. i had a 12lb unit in there for a long time, and beat the snot out of it. all that hard shifting resulted in the shaft deflecting, and ultimately working the bearing loose. a slit tube would let this happen a lot faster. an 18lb flywheel should reduce this effect a little bit from what the 12lb unit would allow, but would still ultimately have the problem.



i am now having the super bearings installed in my solid tube. hopefully this should mitigate the issues created by the single mass flywheel. between that and the S2 harmonic dampener, and a modification i have now made to the flywheel, it "should" stay put.



we'll see