Thrust bearing failure TBF
10-24-2008, 11:40 PM
#61
Addict
Rennlist Member
Rennlist Member
It seems that most are recommending yearly flexplate pre-load checks and you hear tales of frequent needs to re-adjust. Then I think of the thousands of 928s that have likely never been checked, ever. Then one has to wonder how many 928s change hands with some thrust bearing damage?
It just underscores the need for a complete PPI....but this is not a simple matter as thrust bearing checks are not common and they are not something a person can do easily...nor do many sellers want people messing around under their cars with wrenches.
As such, it would seem that TBF must really be quite uncommon in the larger picture....or there are more than a few cars running around "out there" that must have some TB damage.
Jim started this thread with a couple of nightmare situations. It would be a very sad day to find that a car you had just purchased had TBF. That's one reason I'm sticking to 5 speed manuals.
This is unfortunate since the 928 auto trans is a very strong unit.
Just thinking...
H2
It just underscores the need for a complete PPI....but this is not a simple matter as thrust bearing checks are not common and they are not something a person can do easily...nor do many sellers want people messing around under their cars with wrenches.
As such, it would seem that TBF must really be quite uncommon in the larger picture....or there are more than a few cars running around "out there" that must have some TB damage.
Jim started this thread with a couple of nightmare situations. It would be a very sad day to find that a car you had just purchased had TBF. That's one reason I'm sticking to 5 speed manuals.
This is unfortunate since the 928 auto trans is a very strong unit.
Just thinking...
H2
10-24-2008, 11:41 PM
#62
Inventor
Rennlist Member
Rennlist Member
At some point in MY 1984 Porsche stopped using these parts. Porsche should have re-designed the clamp at that point but did not.
Another Porsche blunder in our opinion was when they changed the constant diameter 25mm drive shaft to the necked down 28mm one which has shearing issues.
Another Porsche blunder in our opinion was when they changed the constant diameter 25mm drive shaft to the necked down 28mm one which has shearing issues.
I have a four post lift now like Bill, and I, ahem, 'relieve the pressure' about once a month. If I had to rebuild the torque tube, I'd probably get one of your clamps.
I hope I don't sound preachy when I have to point out all the ways Jim Bailey is missing the point when he says the factory tensioner has worked well for 25 years?
10-25-2008, 12:09 AM
#63
Former Vendor
Join Date: Feb 2004
Posts: 2,139
Likes: 0
Received 0 Likes
on
0 Posts
Ken,
Thanks for the clarification! And good point about the 968 belt tensioner.
As far as sounding "preachy" I know I'm one of the biggest violators when it comes to certain TBF issues.
Kind regards,
Constantine
Thanks for the clarification! And good point about the 968 belt tensioner.
As far as sounding "preachy" I know I'm one of the biggest violators when it comes to certain TBF issues.
Kind regards,
Constantine
Why didn't they change to a hydraulic belt tensioner for the GTS in '93, when the 968 got one in '92?
The 'while back' period was before your superclamp, and the query was if someone had tried using two factory clamps.
I have a four post lift now like Bill, and I, ahem, 'relieve the pressure' about once a month. If I had to rebuild the torque tube, I'd probably get one of your clamps.
I hope I don't sound preachy when I have to point out all the ways Jim Bailey is missing the point when he says the factory tensioner has worked well for 25 years?
The 'while back' period was before your superclamp, and the query was if someone had tried using two factory clamps.
I have a four post lift now like Bill, and I, ahem, 'relieve the pressure' about once a month. If I had to rebuild the torque tube, I'd probably get one of your clamps.
I hope I don't sound preachy when I have to point out all the ways Jim Bailey is missing the point when he says the factory tensioner has worked well for 25 years?
Last edited by Black Sea RD; 10-25-2008 at 09:08 AM.
10-25-2008, 01:54 AM
#64
Bill,
I followed the change out of the torque tube when the shaft failed. A very interestig thread. I have saved it off onto my files for reference if ever needed.
Constantine,
As stated in some of my previous post, I really like the design of your clamp and I believe that it is the best solution for the problem of migration and possible TBF. I applied loctite a few years ago and no migration and I can spring the flexplate to check end play with dial indicator. I have also checked the aft clamp and checked the torque on Allen Headed lock bolt and in good order and condition.
I have the data sheet for the loctite and decided if and when I have to remove the clamp, out will come my trusty butane blow torch and fire extinguisher.
If and when I have to remove the torque tube, I will purchase one of your clamps and fit it.
Tails 1990 928 S4 Auto
I followed the change out of the torque tube when the shaft failed. A very interestig thread. I have saved it off onto my files for reference if ever needed.
Constantine,
As stated in some of my previous post, I really like the design of your clamp and I believe that it is the best solution for the problem of migration and possible TBF. I applied loctite a few years ago and no migration and I can spring the flexplate to check end play with dial indicator. I have also checked the aft clamp and checked the torque on Allen Headed lock bolt and in good order and condition.
I have the data sheet for the loctite and decided if and when I have to remove the clamp, out will come my trusty butane blow torch and fire extinguisher.
If and when I have to remove the torque tube, I will purchase one of your clamps and fit it.
Tails 1990 928 S4 Auto
10-25-2008, 04:47 AM
#65
Rennlist Member
What is the overall experience on Loctite 290? I know that some guys used it with good results. I replaced my torque converter bearings in 2005 and installed a rebuilt TT from 928specialists. I glued the flexplate back then with Loctite. No problems ever since, no movement 
10-25-2008, 11:55 AM
#67
Captain Obvious
Super User
Super User
Why didn't they change to a hydraulic belt tensioner for the GTS in '93, when the 968 got one in '92?
The 'while back' period was before your superclamp, and the query was if someone had tried using two factory clamps.
I have a four post lift now like Bill, and I, ahem, 'relieve the pressure' about once a month. If I had to rebuild the torque tube, I'd probably get one of your clamps.
I hope I don't sound preachy when I have to point out all the ways Jim Bailey is missing the point when he says the factory tensioner has worked well for 25 years?
The 'while back' period was before your superclamp, and the query was if someone had tried using two factory clamps.
I have a four post lift now like Bill, and I, ahem, 'relieve the pressure' about once a month. If I had to rebuild the torque tube, I'd probably get one of your clamps.
I hope I don't sound preachy when I have to point out all the ways Jim Bailey is missing the point when he says the factory tensioner has worked well for 25 years?
10-25-2008, 04:43 PM
#68
Instructor
Join Date: Dec 2007
Location: Gothenburg, Sweden
Posts: 128
Likes: 0
Received 0 Likes
on
0 Posts
torque
The earlier 4 speed torque tubes have a snap ring groove at the front and the workshop manual discusses using spacer washers of .5 mm , 1 mm, and 1.5 mm to make it IMPOSSIBLE for the clamping collar to slide forward ( shaft to pull back) around 1986 Porsche issued a technical bulletin stating that this was no longer necessary and STOPPED installing the ring and spacers at the factory or when replacing tubes at the dealership......the groove was deleted when the larger diameter shaft was introduced in about 1990. The clamp bolt torgue is 80 Nm it is a 12.9 material higher strength bolt.
Is it a good idea to replace the stock allenbolt in the clamp to common six-point 12,9 bolt instead? What material (stengthnumber) does the stock allenbolt got?
My car is an 32v 86 with auto.
/Tobias
10-25-2008, 05:49 PM
#69
Team Owner
the stock allen bolt is a 6 point and its a 12.9 this is about as strong as you will find. Use Blue loctite on the bolt threads and you want to make sure that the bolt you use has the thicker shank. Usually the rear pinch is more loose than the front so make sure to check this bolt as well, you might have to realign the shaft to fit in the rear coupler
10-25-2008, 07:02 PM
#70
Dont bash me, we all have a rite to our opinion but this is 5 pages of nonsense my car has 107k on it ,if its gona happen it would of allready,after you make these adjustments for tbf,then drive a block down the road, it goes back to where it originally was when you started,im just guessing on that but like dr.spock says its logical. corn
10-25-2008, 07:55 PM
#71
Captain Obvious
Super User
Super User
Dont bash me, we all have a rite to our opinion but this is 5 pages of nonsense my car has 107k on it ,if its gona happen it would of allready,after you make these adjustments for tbf,then drive a block down the road, it goes back to where it originally was when you started,im just guessing on that but like dr.spock says its logical. corn
The TBF on the 32V autos is a documented problem.
10-26-2008, 01:40 AM
#72
Addict
Rennlist Member
Rennlist Member
Dont bash me, we all have a rite to our opinion but this is 5 pages of nonsense my car has 107k on it ,if its gona happen it would of allready,after you make these adjustments for tbf,then drive a block down the road, it goes back to where it originally was when you started,im just guessing on that but like dr.spock says its logical. corn
My car suffered a TBF at around 149K miles.
10-26-2008, 08:56 AM
#73
Former Vendor
Join Date: Feb 2004
Posts: 2,139
Likes: 0
Received 0 Likes
on
0 Posts
Hi Wade,
Any details on your TBF. As in "Everything was fine then one day it started to..."
Always a bit interesting to hear about some of the weird sypmtoms and how the final diagnosis was made, if it's not too prying or painful to recount.
Thank you,
Constantine
Any details on your TBF. As in "Everything was fine then one day it started to..."
Always a bit interesting to hear about some of the weird sypmtoms and how the final diagnosis was made, if it's not too prying or painful to recount.
Thank you,
Constantine
Last edited by Black Sea RD; 10-26-2008 at 10:44 AM.
10-26-2008, 11:26 AM
#74
Addict
Rennlist Member
Rennlist Member
What is the overall experience on Loctite 290? I know that some guys used it with good results. I replaced my torque converter bearings in 2005 and installed a rebuilt TT from 928specialists. I glued the flexplate back then with Loctite. No problems ever since, no movement
__________________
Schocki
I developed the "LOCTITE FIX" about 8 years ago and have never heard of TBF on a car that it has been applied. The only negative that I know of is that you have to use a lot of heat to undo it if you have to remove the driveshaft.
For more info go to http://members.rennlist.com/captearlg/loctitefix.html
__________________
Schocki
I developed the "LOCTITE FIX" about 8 years ago and have never heard of TBF on a car that it has been applied. The only negative that I know of is that you have to use a lot of heat to undo it if you have to remove the driveshaft.
For more info go to http://members.rennlist.com/captearlg/loctitefix.html
10-26-2008, 11:39 AM
#75
Team Owner
FWIW my suggestion is to only use the loctite on the bolt threads not the flex plate clamp, adding loctite to this part will add more grip to the splines/shaft.
BUT when its time to remove it, I think that adding heat to break the grip may also damage the clamp, not to mention the need to clean out the splines.. Remember that the driveshaft will be running in the temp range somwhere from ambient to 250 deg ( estimated) this will depend on how long the system is in operation and how long the car is not moving. The cats seem to do a pretty good job of heating the drive line especially when the car is in stop and go driving
BUT when its time to remove it, I think that adding heat to break the grip may also damage the clamp, not to mention the need to clean out the splines.. Remember that the driveshaft will be running in the temp range somwhere from ambient to 250 deg ( estimated) this will depend on how long the system is in operation and how long the car is not moving. The cats seem to do a pretty good job of heating the drive line especially when the car is in stop and go driving
