porsche928guy

Leslie...according to Jim (sounds like a TV show) the plates have no balance relation to each other. The scallops are there to balance the plate/clamp unit in the front and plate/shaft unit in the rear. So I think you are OK there.

David...have you tried to unbolt the TC completely from the rear plate and start the car? I talked with Andre at Edge and he suggested doing that to see if the vibration was still there. I guess that would probably tell us definitively if it is the TC. If the vibs are still there then we know it is for sure forward of the TC.


I won't be able to do that until the end of the month so if you get some time to do it please let me know your results

928ntslow

Interesting. I read this thread a couple of times. Seems you guys are moving the "issue" around by changing the position. The vibration happens, based on the changed position, causing the change at a different rpm, regardless of the vehicle stopped or moving. Forgive me for pointing out the obvious, but sometimes that's where we sometimes have to work from.

Essentially, something appears out of balance, but personally, I don't think that is the issue as none of these things are perfectly balanced to begin with. If something was way out of balance, it would be more constant and not just concentrated to a small rpm range. Because of the combined rotating mass of any of these components, the sum creates its own "frequency" level. I suspect that as the mass turns, there is enough "play" in either the bearings of the TT (most likely) or the TC.. this could also be emanating from the rear of the crank, but I kind of doubt it.

So lets say the shaft of the TT was not perfectly straight just laying on a flat surface. The shaft is flexible, as it should be and the 3 bearings in the tube control flex and keep the shaft in a straight position. IF the shaft was distorted during removal for the rebuild or when re-installed, you would think the bearings would compensate for this. However, if by chance, the position of the shaft on the tube is in such a position to move laterally, the bearings would distort at a given rotating frequency. I suspect the dampers were installed in the TT's to additionally compensate for this as well.

Who knows what the TT factory did to make sure the TT's did not resonate. They may have had a machine that they hooked up each TT to and turned them at high rpm with a sensor of some sort to check for vibration and at what rpm and frequency. Any issues and it gets rebuilt right there at the factory.

The guy(s) who rebuilt the TT may not have had anything more than a block and hammer as this probably works 95% or so of the time. Not knocking the re builder...just guessing.

So IMHO, the shaft in the TT is set in such a way that it is resonating at a particular frequency causing you vibration. Changing the position of the attached components only moves that resonation to another frequency appearing at a different rpm range.

ADDED: Sometimes, just moving the position of a bearing will correct the lateral flex in the shaft.

Jim bailey - 928 International

Keith the rebuilt TT is one of our's and no one on earth has rebuilt as many as our Mr Boonrung. He uses a hydroulic ram with a ten foot reach to press them apart and carefully positions the carriers as he assembles them. The flywheel , flex plates , and torque convertor are ALL individually balanced that way they CAN be replaced. The modified torque convertor is the most likely suspect simply BECAUSE it was modified. The way they rebuild one is to cut it apart , then bend or trim the turbine blades before welding it back together and THEN they balance it. The potential for error exists in EACH of those steps . Also the rebuilder in his mind is rebuilding a Mercedes convertor which in that application is bolted to the flywheel with the transmission directly behind it....no torque tube , no driveshaft , no rear flexplate ..... As with all our parts we warranty them for one year so if it does end up being an issue with the tube we would send a replacement at no charge.

porsche928guy

I want to go on record as saying I'm not trying to point fingers at anyone. All I know is that I've done everything by the book and have a vibration. Before I go spend another weekend (or two or three...I work slow) on my back tearing things apart I want to go after the most likely candidate. I have total confidence in the TT rebuild and the record of successful rebuilds speaks for itself. I agree with Jim that there is more margin for error with the TC "upgrade" and far more successful 928Intl. TT rebuilds on record than Edge TC upgrades.

But...I'm still failing to understand how the TC can be at fault if the vibration changes when rotating the rear plate to a new position on the TC. I'm not saying it isn't possible. I'm just looking for a good sound reason as to how it could be the TC given the facts at hand.

928ntslow

Nice, that takes out the guess work of how it was done. Of course that doesn't mean an issue in the TT doesn't exist, but as stated, the easiest solution right now may be to swap the TC. I'm still stickin' to my SWAG.

Since you had noted it Jim, maybe one of the balance weights was thrown on any of those components. ANYTHING can happen as you, more than most others would know.

Jim bailey - 928 International

Same logic applies the torque tube...."the vibration changes when rotating the rear plate to a new position on the TC. " If there were a problem with the torque tube how would rotating the flex plate location change that ? If you change both of them we still will not KNOW.... You have another stock torque convertor already but I know the modified one gives the car so much more snap !! You want to run it

928ntslow

Right, so if the TC was not perfectly balanced either, than the frequency would change. Even the smallest weight change would cause an effect. Don't get me wrong, not trying to split hairs or anything like that. Like everyone else, trying to throw some possibilities out there to rectify the issue. BTW, never meant to insinuate the TT guy was a hack. Even with the best production facilities, they spot check every so often because defects can arise.

Mrmerlin

I would advise against disconnecting the torque converter from the flex plate and letting it spin with the engine running.
What will happen is the torque converter snout will seize in the rear side of the flex plate.it is a precision fit and once one part starts spinning without the other heat will be generated and then seizure will occur
Then you will have a welded torque converter /flex plate, IE it will not be able to be removed

porsche928guy

MrMerlin...thanks for watching our back on that.

David...ABORT! on that suggestion from Andre. I would like to think I would have caught that before trying it myself but maybe not.

I think I'll just put my known factory TC back in and see what happens. At this point that sounds like the best option based on the advice of the more sagely 'listers. Thanks to everyone for your help. I'll report back when I have something meaningful to add...

David L. Lutz

Don't know why, but I was always worried about disconnecting the TC and runing the engine. Glad we were saved on that one.

I too for some weird reason think its the Torque Converter. Now to add to that frustration I am starting to get a noise from it at idle. I sounds like "Scraping a wire brush on a washboard" for a second or two and then goes away. No noise under load.

We may just have to get back with Edge because with the higher stall speed its a blast off the line. (am I am not giving up on that!) A completely different car.

I think its really neccesary with the Murf kit, it really spools up the blower in a hurry!

Mrmerlin

when you refit the TC try to make the alignment so when the engine is at TDC the drain plug is facing the opening on the bottom of the grate. Its not hard to do just put the engine at TDC after you remove the rear coupler bolt, then refit the TC with the drain at the bottom and button er up.
While you have the TC out see if you can acertain the location of the rear TT damper, you will have to have the rear front part of the bellhousing off though

porsche928guy

Hello again faithful readers! Swapped out the Edge TC with the known factory original TC and bolted the rear plate to the TC in all 3 positions...vibrations are still there.

What say ye? I think that pretty well eliminates the TC as the source of the problem and leaves the TT. Is there anything I'm missing?

928ntslow

Aaaaaaaa...very sorry to hear this! I was hoping I was wrong and others were right on the TC. I have known 4 other folks who had their TC's converted by Edge (including me years ago) and none that I know of have ever had a vibration. So, I don't know where that rumor stated.

I guess the next easiest thing to do is swap the TT. Not much more work than doing the TC. You don't even have to drop the tranny for this.

Definitely let us know what happens!

Good luck!

David L. Lutz

Jeremy,

Man this post is just in time. I have been searching around and almost purchased another Torque Converter thinking that was our problem!

I owe you one

I have been so busy sorting out some other issues I have not been able to address my vibration.

So at this point I guess we have to lean towards the Torque Tube. I listened closely to what Jim posted about the rebuilds earlier and I still don't question or have any doubts about the quality of the product when it leaves their shop. But could something be happening in shipping? The tube weighs a ton and has the drive shaft sticking out of both ends...etc...

I ask this because on the first tube I received it was beat to hell and back by UPS to the point the shaft was knocked loose and the new bearings were loose in the tube. That was of course quickely solved and another tube was sent and when I received it all looked good.
(actually it was the orginal tube/shaft that was in my car, but just rebuilt)

I did have to tap the shaft to the rear slightly for it to line up IIRC other than that there was no rattles and the shaft turned freely.

I am just asking because maybe the damper or something could shift or get knocked out of line. Or maybe in shipping the shaft took a hard lick and is slightly bent? I just don't know?

I am searching (as well as you) for the solution because I was convinced that I would be reading this your post some day and it would of been the TC.

Thanks again for all your hard work, please keep us posted.

porsche928guy

I was hopeful that it was the TC but I guess this eliminates it 100%? I still might send mine back to Edge to have them double check the balance.

My rebuilt TT from Intl came in and was in great shape no damage to the box or anything like that so my experience there sounds completely different. I did inspect it pretty darn closely and all looked good to me.

Does anyone have any suggestions?