Help with vibration
10-07-2008, 04:33 PM
#16
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Bill... I noticed the scallops in both flex plates. The rear plate was never detached from the shaft that runs through the TC housing and the front plate was never detached from the clamp unit. The front plate was bolted back up in its original position respective to the flywheel.
To your suggestion on disconnecting the TT shaft... how would this be accomplished? As I recall removing the pinch bolt from the couplers doesn't allow the shaft to spin free. Would I have to remove the TT
?
Also...just thinking as I go along here...if it was the TC wouldn't the vibration remain at the same RPM range regardless of which of the three positions the rear plate was attached to the TC? In this case the vibration changes RPM at each position.
So by my logic (which might be flawed) if everything is balanced up to the TC and the TC is causing the problem, rotating the plate to bolt up to the next set of holes on the TC shouldn't change the vibration...but it does. Does that not point to something forward of the TC?
To your suggestion on disconnecting the TT shaft... how would this be accomplished? As I recall removing the pinch bolt from the couplers doesn't allow the shaft to spin free. Would I have to remove the TT
?Also...just thinking as I go along here...if it was the TC wouldn't the vibration remain at the same RPM range regardless of which of the three positions the rear plate was attached to the TC? In this case the vibration changes RPM at each position.
So by my logic (which might be flawed) if everything is balanced up to the TC and the TC is causing the problem, rotating the plate to bolt up to the next set of holes on the TC shouldn't change the vibration...but it does. Does that not point to something forward of the TC?
10-09-2008, 04:46 AM
#18
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I think he's saying disconnect the flexplate from the flywheel and see what you get.
10-09-2008, 02:23 PM
#19
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Bill... I noticed the scallops in both flex plates. The rear plate was never detached from the shaft that runs through the TC housing and the front plate was never detached from the clamp unit. The front plate was bolted back up in its original position respective to the flywheel.
To your suggestion on disconnecting the TT shaft... how would this be accomplished? As I recall removing the pinch bolt from the couplers doesn't allow the shaft to spin free. Would I have to remove the TT?
Also...just thinking as I go along here...if it was the TC wouldn't the vibration remain at the same RPM range regardless of which of the three positions the rear plate was attached to the TC? In this case the vibration changes RPM at each position.
So by my logic (which might be flawed) if everything is balanced up to the TC and the TC is causing the problem, rotating the plate to bolt up to the next set of holes on the TC shouldn't change the vibration...but it does. Does that not point to something forward of the TC?
To your suggestion on disconnecting the TT shaft... how would this be accomplished? As I recall removing the pinch bolt from the couplers doesn't allow the shaft to spin free. Would I have to remove the TT
?Also...just thinking as I go along here...if it was the TC wouldn't the vibration remain at the same RPM range regardless of which of the three positions the rear plate was attached to the TC? In this case the vibration changes RPM at each position.
So by my logic (which might be flawed) if everything is balanced up to the TC and the TC is causing the problem, rotating the plate to bolt up to the next set of holes on the TC shouldn't change the vibration...but it does. Does that not point to something forward of the TC?
If you will remember we discussed this a while back and I too rotated the rear flex plate where it bolts on the TC and I had exactly the same issues. With the postition its in now I only get the harsh vibration at around 3800-4000 rpm.
But, my point it did change with position.
I did bolt my front flex plate exactly where it was on the fly wheel before I removed it. Also just one more bit of info I did install the constantine clamp which I assume is balanced.
It sounds from Rogers comment we both got our rebuilt TT from the same source and had our TC modified by Edge Racing. (I also installed new tranny mounts and the motor mounts are 2yrs old)
Even thought I have checked my tranny measurments twice from side to side (at the mounts) and it does not appear I need shimms.
Just a thought . . . I really don't know if some how the drive train was in a bind (not shimmed properly) would cause our vibration or not?
I can't really add much more at this point as I have been really busy working the bugs out of the SC and now have a leaking radatior!
Please lets us know if you find the cause.
10-09-2008, 04:57 PM
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David,
Good luck with the mound of work in front of you. We are in the same boat here.
Does your vibration change RPM ranges when you've rotated the rear flex plate?
My thinking at this point is that if the TC was at fault the vibration would remain at the same RPM range no matter what position the rear flex plate was mounted to the TC.
I was gonna call Roger but I think he's out getting a car right now so I didn't want to bug him. I'll probably call early next week to pick his brain.
Good luck with the mound of work in front of you. We are in the same boat here.
Does your vibration change RPM ranges when you've rotated the rear flex plate?
My thinking at this point is that if the TC was at fault the vibration would remain at the same RPM range no matter what position the rear flex plate was mounted to the TC.
I was gonna call Roger but I think he's out getting a car right now so I didn't want to bug him. I'll probably call early next week to pick his brain.
Last edited by porsche928guy; 10-09-2008 at 05:23 PM.
10-09-2008, 06:41 PM
#21
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Yes, the vibration did change RPM ranges when I rotated the rear flex plate. In the orginal position I had it in the vibration was bad at 3000 - 3500, now after 2 rotations more it has moved to the 4000 range. Thats where I have left it.
The only reason I am leaning toward the TC or something assoicated with it, is that we both had Edge Racing modify them. (but, I cannot find any others posting about a problem with that mod.)
I also replaced my 2 TC bearings and had a good Tranny shop press them in and all looked good. I did have a small problem getting my TC seated back into the tranny and during that process I think I might have nicked the new seal, because now I have a few drops of fluid leaking from the seal area. However, I don't think that is causing my vibration.
Did you shimm at the new tranny mounts?
The only reason I am leaning toward the TC or something assoicated with it, is that we both had Edge Racing modify them. (but, I cannot find any others posting about a problem with that mod.)
I also replaced my 2 TC bearings and had a good Tranny shop press them in and all looked good. I did have a small problem getting my TC seated back into the tranny and during that process I think I might have nicked the new seal, because now I have a few drops of fluid leaking from the seal area. However, I don't think that is causing my vibration.
Did you shimm at the new tranny mounts?
10-10-2008, 11:53 AM
#23
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David,
I called Jim yesterday at International. We had a good conversation and our problem didn't make much sense to him either. He said he'd think on it, talk it over with the crew and get back to us. Fortunately for us we have some of the best people in the biz in our corner!
Now get back to sorting the SC!
I called Jim yesterday at International. We had a good conversation and our problem didn't make much sense to him either. He said he'd think on it, talk it over with the crew and get back to us. Fortunately for us we have some of the best people in the biz in our corner!
Now get back to sorting the SC!
10-20-2008, 01:59 PM
#24
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Alright...just talked with Roger for a bit and it looks like I'm down to removing the TT 
unless anybody has some other thoughts. Not looking forward to doing this again!
unless anybody has some other thoughts. Not looking forward to doing this again!
10-20-2008, 11:33 PM
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Kevin has been reading this thread with interest. He's wondering if those scallops in the flexplates were meant to offset each other, and should be set in opposing positions to each other....or were they supposed to be positioned together? Has anyone figured this out yet?
10-21-2008, 10:57 AM
#27
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I have been reading the thread again and come back to the conclusion that its the TT or the TC.
With respect to the TT there are a lot of the rebuilt units out there and no one else is getting the same vibration issues as you two. The TC was modified and you are both getting a problem.
Anyone else with the edge modified TC ??
Using logic its the TC. Just my 5c worth
It may be easier to change out the TC with a stock unit and try that. This would find the culprit with less hassle.
With respect to the TT there are a lot of the rebuilt units out there and no one else is getting the same vibration issues as you two. The TC was modified and you are both getting a problem.
Anyone else with the edge modified TC ??
Using logic its the TC. Just my 5c worth
It may be easier to change out the TC with a stock unit and try that. This would find the culprit with less hassle.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
10-21-2008, 12:21 PM
#28
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David and Leslie...I guess we're down to thinking that the TT is the most likely candidate. Both you and I have done the same things.
1) Replaced TT from the same source
2) Upgraded TC from the same source
3) Replaced tranny mounts
4) Replaced TC housing bearings
5) Replaced various seals.
We are both having the same issues. I think it is pretty much the consensus that the source of the vibration has to be somewhere behind the engine and forward of the TC. So that leaves front flexplate, flywheel, TT, converter housing internals and rear flex plate/short shaft. We come to this conclusion by the following:
1) The vibration occurs at different RPM ranges depending on where the rear plate is attached to the TC...thus eliminating the TC and everything behind it.
2) Both of us were careful about bolting the front plate at the same location to the flywheel thus maintaining any balance that was there from the factory.
3) If we know one thing its that Porsche engineers sometimes to the point of over-engineering. I'm not saying that they couldn't have missed something but Jim said, and I agree, that if something was supposed to be aligned a certain way it would have been indexed or at least noted in the WSM.
4) We aren't the first ones to change out a TT. If the front and rear plates were supposed to be aligned somehow I'm sure somebody else would have said something before now.
So we're down to the TT and the converter housing components. Both of us got the TT from the same place and both of us had a shop put the converter bearings in for us. In talking with Roger he indicated that he thought it should be pretty obvious if somebody screwed up the TC housing bearings and everything there looked good to me.
Trust me I'm not wild about changing the TT out again. So if anybody has any ideas PLEASE don't hesitate to post.
1) Replaced TT from the same source
2) Upgraded TC from the same source
3) Replaced tranny mounts
4) Replaced TC housing bearings
5) Replaced various seals.
We are both having the same issues. I think it is pretty much the consensus that the source of the vibration has to be somewhere behind the engine and forward of the TC. So that leaves front flexplate, flywheel, TT, converter housing internals and rear flex plate/short shaft. We come to this conclusion by the following:
1) The vibration occurs at different RPM ranges depending on where the rear plate is attached to the TC...thus eliminating the TC and everything behind it.
2) Both of us were careful about bolting the front plate at the same location to the flywheel thus maintaining any balance that was there from the factory.
3) If we know one thing its that Porsche engineers sometimes to the point of over-engineering. I'm not saying that they couldn't have missed something but Jim said, and I agree, that if something was supposed to be aligned a certain way it would have been indexed or at least noted in the WSM.
4) We aren't the first ones to change out a TT. If the front and rear plates were supposed to be aligned somehow I'm sure somebody else would have said something before now.
So we're down to the TT and the converter housing components. Both of us got the TT from the same place and both of us had a shop put the converter bearings in for us. In talking with Roger he indicated that he thought it should be pretty obvious if somebody screwed up the TC housing bearings and everything there looked good to me.
Trust me I'm not wild about changing the TT out again. So if anybody has any ideas PLEASE don't hesitate to post.
10-21-2008, 12:33 PM
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Roger...just saw your post.
I'm not necessarily disagreeing with you but I feel that if it was the TC the vibration would stay constant and at the same RPM range no matter what position the rear plate was bolted in.
Again...not trying to argue I just would like to hear some logic pointing to the TC given the change in vibration with change in bolting position to the TC.
I'm not necessarily disagreeing with you but I feel that if it was the TC the vibration would stay constant and at the same RPM range no matter what position the rear plate was bolted in.
Again...not trying to argue I just would like to hear some logic pointing to the TC given the change in vibration with change in bolting position to the TC.
10-21-2008, 12:46 PM
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Jeremy, Kevin didn't get a TT from anywhere but our own garage. Leftovers from a previous car. We didn't get the TC modified by Edge, either....so our problems probably are not the same.
But we still had vibration after the TT was swapped out....it may have been from the engine troubles that were brewing. But Kevin's still pondering that flexplate question anyway.
If anyone comes up with anything about the significance of positioning the flexplates, we'd like to hear it.
But we still had vibration after the TT was swapped out....it may have been from the engine troubles that were brewing. But Kevin's still pondering that flexplate question anyway.
If anyone comes up with anything about the significance of positioning the flexplates, we'd like to hear it.