Thrust Bearing Failure - Why is this happening ?
03-01-2009, 08:52 PM
#16
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Hi Andrew,
Having done a lot of research into the TBF problem for automatic 928s, I believe I can speak with some authority on this subject. Bottom line is, releasing the pressure once a year or everytime someone is under the car is just not good enough. Forward pressure on the front flex plate can and does result in TBF, and is one of the main causes of TBF cases in automatic 928s.
As far as a vested interest, yes you are right. After researching the TBF problem and causes, I set about trying to come up with a solution that bested any other solution out there to arrest the drive shaft pullout from the front flexplate that causes most of the forward pressure problems. After a few years and $$$$$ of R&D we came up with the 928 Super Clamp, aka the Constantine clamp (still don't care for that name), a picture of which DR kindly has posted in this thread.
We do believe the clamp is one of the best things you can do for your automatic 928 for what it can stop from happening. Rebuilding a 928 engine is not kind to anyone's wallet and the price of putting in a Super Clamp WYIT doing a TT R&R or other maintenance just makes sense. Sorry that bothers you.
I have staked my reputation on that little device, a lot more than say, someone who throws out poor advice that is not learned but merely circulated like an urban legend from what others have said.
For instance, tigthening the front pinch bolt to 65 ft. lbs. was only one step of a two step process which was given by Porsche AG techs when contacted by private mechanics about a drive shaft pullout problem at the front flexplate which kept recurring to the 928 automatic they were servicing. The first step given by the Porsche AG techs was to replace the old flex plate with a new one. As this story became circulated among 928 auto owners, the new flexplate part of the Porsche AG tech's recommendation was dropped, I suspect due to the cost of a new flexplate. So now tigthening the front pinch bolt to 65 ft. lbs. is passed along as a good thing to do. Our research has found this to not be true and has little effect on the drive shaft pull out problem.
But I digress, I guess you don't have to worry about any of this being a 5 speed owner.
Cheers,
Constantine
Having done a lot of research into the TBF problem for automatic 928s, I believe I can speak with some authority on this subject. Bottom line is, releasing the pressure once a year or everytime someone is under the car is just not good enough. Forward pressure on the front flex plate can and does result in TBF, and is one of the main causes of TBF cases in automatic 928s.
As far as a vested interest, yes you are right. After researching the TBF problem and causes, I set about trying to come up with a solution that bested any other solution out there to arrest the drive shaft pullout from the front flexplate that causes most of the forward pressure problems. After a few years and $$$$$ of R&D we came up with the 928 Super Clamp, aka the Constantine clamp (still don't care for that name), a picture of which DR kindly has posted in this thread.
We do believe the clamp is one of the best things you can do for your automatic 928 for what it can stop from happening. Rebuilding a 928 engine is not kind to anyone's wallet and the price of putting in a Super Clamp WYIT doing a TT R&R or other maintenance just makes sense. Sorry that bothers you.
I have staked my reputation on that little device, a lot more than say, someone who throws out poor advice that is not learned but merely circulated like an urban legend from what others have said.
For instance, tigthening the front pinch bolt to 65 ft. lbs. was only one step of a two step process which was given by Porsche AG techs when contacted by private mechanics about a drive shaft pullout problem at the front flexplate which kept recurring to the 928 automatic they were servicing. The first step given by the Porsche AG techs was to replace the old flex plate with a new one. As this story became circulated among 928 auto owners, the new flexplate part of the Porsche AG tech's recommendation was dropped, I suspect due to the cost of a new flexplate. So now tigthening the front pinch bolt to 65 ft. lbs. is passed along as a good thing to do. Our research has found this to not be true and has little effect on the drive shaft pull out problem.
But I digress, I guess you don't have to worry about any of this being a 5 speed owner.
Cheers,
Constantine
I understand that's your opinion and your vested interest, but I respectfully disagree. There are many people on this list that use the annual release method without any issues. Obviously only time will tell if this method is as statistically effective as the others (Constantine clamp, locktite, etc.) but the price is right.
I should append my previous post by saying that the the majority of people on this list that use the annual pre-load release method, tighten the stock clamp to 65 ftlbs (vs. the spec of 55 IIRC) as a means to mitigate the migration along the shaft.
Finally, this serves as another reason why you should have a 5-speed.
I should append my previous post by saying that the the majority of people on this list that use the annual pre-load release method, tighten the stock clamp to 65 ftlbs (vs. the spec of 55 IIRC) as a means to mitigate the migration along the shaft.
Finally, this serves as another reason why you should have a 5-speed.
03-01-2009, 09:03 PM
#17
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Hi Feargal,
Again, sorry to hear about this. I have talked to a few of people in your position and it is not an envious position to say the least.
Before buying any parts I would recommend, if this hasn't been done already, the engine be removed, torn down and the internal parts examined closely to find just what has been damaged and what can be salvaged. Then go from there as to what your course of action should be.
There are a few resources on this forum which can help you and possibly your mechanics in figuring this all out. One such resource is Greg Brown who posts to this list and is probably the most knowledgable 928 engine builder we have.
Please feel free to contact me by PM or at constantine@blackseard.com if you want to bounce something off someone other than this forum.
Best regards,
Constantine
Again, sorry to hear about this. I have talked to a few of people in your position and it is not an envious position to say the least.
Before buying any parts I would recommend, if this hasn't been done already, the engine be removed, torn down and the internal parts examined closely to find just what has been damaged and what can be salvaged. Then go from there as to what your course of action should be.
There are a few resources on this forum which can help you and possibly your mechanics in figuring this all out. One such resource is Greg Brown who posts to this list and is probably the most knowledgable 928 engine builder we have.
Please feel free to contact me by PM or at constantine@blackseard.com if you want to bounce something off someone other than this forum.
Best regards,
Constantine
I haven't posted, but I do read a lot on here - mostly due to the fact that I'm a newbie and don't feel accomplished enough to comment.
Over the past few months I have read plenty of stuff about TBF, just a pity I hadn't read it sooner and done something about it. I have also read about your clamp, loctite and even guys who have welded the shaft !
My block damage is not as bad as the pictures of TBF I have seen on here - but I'm told it's bad enough to mean it is scrap.
It has about 2-3mm groove at thrust face of block.
Over the past few months I have read plenty of stuff about TBF, just a pity I hadn't read it sooner and done something about it. I have also read about your clamp, loctite and even guys who have welded the shaft !
My block damage is not as bad as the pictures of TBF I have seen on here - but I'm told it's bad enough to mean it is scrap.
It has about 2-3mm groove at thrust face of block.
03-02-2009, 12:06 AM
#19
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Constantine,
As you know I have the greatest respect for you and the Constantine Clamp and indeed sell them.
They are, unfortunatly, very expensive for most 928 owners and out of the question as a quick fix for most owners.
Checking the flexplate on an annual basis and releasing the pressure has got to be EXCELLENT advice for most owners as this has to be the only option for them.
A lot of us have used the Loctite fix and have not seen any further movement of the flexplate or increase in crank movement. So this method does work contary to what you think. So for those that cannot afford the Constantine clamp we must offer alternative methods of reducing the instances of TBF.
Roger
As you know I have the greatest respect for you and the Constantine Clamp and indeed sell them.
They are, unfortunatly, very expensive for most 928 owners and out of the question as a quick fix for most owners.
Checking the flexplate on an annual basis and releasing the pressure has got to be EXCELLENT advice for most owners as this has to be the only option for them.
A lot of us have used the Loctite fix and have not seen any further movement of the flexplate or increase in crank movement. So this method does work contary to what you think. So for those that cannot afford the Constantine clamp we must offer alternative methods of reducing the instances of TBF.
Roger
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
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."
03-02-2009, 12:07 AM
#20
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Sorry to hear of yet another TBF.
Yep, there is only one real solution (other than a 5-Speed Conversion).
The 928 Super Clamp https://www.928gt.com/superclamp.htm
Yep, there is only one real solution (other than a 5-Speed Conversion).
The 928 Super Clamp https://www.928gt.com/superclamp.htm
The superclamp appears to be robust and really well made. If I had an automatic, I'd get one.
One thing that scares me away from automatics is not knowing just what condition the thrust bearing is in....and it's not something that most owners will let you crawl under their car with wrenches and check. And I suspect some prepurchase inspectors may not understand it well either. Caveat Emptor.
Harvey
03-02-2009, 12:12 AM
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Hi,
Not really. You should always check to see if there is any pre-load. But with the clamp there probably won't be if it was set up correctly using the instructions that came with it.
Who did the installation, you or your tech?
Hope that answers the question,
Constantine
Not really. You should always check to see if there is any pre-load. But with the clamp there probably won't be if it was set up correctly using the instructions that came with it.
Who did the installation, you or your tech?
Hope that answers the question,
Constantine
03-02-2009, 12:31 AM
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Dear Roger,
First, do you ever sleep?
We have been down this same road which each other before. I understand cost will always be a hindrance to some when buying certain items to include this clamp.
As far as not thinking Loctite works, I never said that. It does but too well when you have to dis-engage it for other maintenance or if it moves and there is preload on the front flexplate again. The methods needed to disengage the drive shaft from the flexplate which include an open flame source, banging on the assembly and which still is not easily done unless one is removing the TT from the car, are the downsides to using Loctite.
As far as cost, everyone will be happy to hear there is a significant price reduction coming on the clamps. However even at the current $480.00, that is pretty inexpensive relative to a TBF rebuild or even compared to other custom parts available to 928ers which do not have the same potential to stop such a disastrous failure from happening to their 928.
By the way, do you have any left?
Kind regards,
Constantine
First, do you ever sleep?
We have been down this same road which each other before. I understand cost will always be a hindrance to some when buying certain items to include this clamp.
As far as not thinking Loctite works, I never said that. It does but too well when you have to dis-engage it for other maintenance or if it moves and there is preload on the front flexplate again. The methods needed to disengage the drive shaft from the flexplate which include an open flame source, banging on the assembly and which still is not easily done unless one is removing the TT from the car, are the downsides to using Loctite.
As far as cost, everyone will be happy to hear there is a significant price reduction coming on the clamps. However even at the current $480.00, that is pretty inexpensive relative to a TBF rebuild or even compared to other custom parts available to 928ers which do not have the same potential to stop such a disastrous failure from happening to their 928.
By the way, do you have any left?
Kind regards,
Constantine
Constantine,
As you know I have the greatest respect for you and the Constantine Clamp and indeed sell them.
They are, unfortunatly, very expensive for most 928 owners and out of the question as a quick fix for most owners.
Checking the flexplate on an annual basis and releasing the pressure has got to be EXCELLENT advice for most owners as this has to be the only option for them.
A lot of us have used the Loctite fix and have not seen any further movement of the flexplate or increase in crank movement. So this method does work contary to what you think. So for those that cannot afford the Constantine clamp we must offer alternative methods of reducing the instances of TBF.
Roger
As you know I have the greatest respect for you and the Constantine Clamp and indeed sell them.
They are, unfortunatly, very expensive for most 928 owners and out of the question as a quick fix for most owners.
Checking the flexplate on an annual basis and releasing the pressure has got to be EXCELLENT advice for most owners as this has to be the only option for them.
A lot of us have used the Loctite fix and have not seen any further movement of the flexplate or increase in crank movement. So this method does work contary to what you think. So for those that cannot afford the Constantine clamp we must offer alternative methods of reducing the instances of TBF.
Roger
03-02-2009, 12:43 AM
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Hi Ron,
Rule of thumb was that the lower HP/TQ of the early U.S. 928 models did not have enough drive shaft wind up to pull the drive shaft out of the front flexplate clamp. Also those cars had a bearing , circlip and washers installed on the end of the drive shaft which kept the drive shaft from being pulled through the flex plate clamp. Those were discontinued sometime in the 1984 model year.
However, all automatic 928s are susceptible to TBF, regardless of year or model. Sometimes it has been found that improper maintenance done by inexperienced techs can induce TBF to happen.
HTH,
Constantine
Rule of thumb was that the lower HP/TQ of the early U.S. 928 models did not have enough drive shaft wind up to pull the drive shaft out of the front flexplate clamp. Also those cars had a bearing , circlip and washers installed on the end of the drive shaft which kept the drive shaft from being pulled through the flex plate clamp. Those were discontinued sometime in the 1984 model year.
However, all automatic 928s are susceptible to TBF, regardless of year or model. Sometimes it has been found that improper maintenance done by inexperienced techs can induce TBF to happen.
HTH,
Constantine
03-02-2009, 12:44 AM
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03-02-2009, 12:50 AM
#29
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Is this clamp a better solution than switching to the pre-85 set up with shims? I seem to recall talk around here about the pre-85 cars not having the TBF issues the later cars did and the shims are why.