Just finished my 1st flex plate / crank end play check
03-12-2014, 11:19 PM
#46
Drifting
Thread Starter
I'll have to wait until April, but this should provide enough driving time to evaluate drive shaft pullout since releasing and re-torquing the front clamp bolt. I'll also check the rear clamp position and bolt condition. I'm keeping an open mind at this point since I haven't made these observations that are critical to having a complete understanding of what is going on. For me all the experience and knowledge of others is invaluable for helping me know what to look for and how to perform the checks and services. But there's no substitute direct observations on my own car. I'll post again in about a month, with pictures, after I've checked both the front and rear. I've learned a lot reading all the comments.
03-13-2014, 07:34 AM
#47
Drifting
Hi Erkka , thats interesting about some mechanics putting stuff in the wrong order ( what on earth does that mean ? ) & how on earth can one get it wrong ? , & the so called Porsche official line ( never seen that in writing ) & if in writing it must be from the period of these cars & not from some desk jocky in this century who is just clutching at anything ,& where did you hear that 3rd hand incorrect info/ myth from anyway ? .
Now lets get back to the real world here , I think you should know something , I working as a Porsche technician ( mechanic ) at major Porsche delership in Sydney Australia from 1977 to 1994 ( 17 years )
While there I ( in the 1980's ) went to 6 x week long Porsche Cars Australia ( Melb) Porsche technical schools ( usually one a year ) & in 1992 I was lucky enough to go to Germany to do a Porsche Tech school at the factory training facility & a hundred or so visits from Porsche in field servive engineers doing a one evening after work mini service school , now the reason I mentioned that is that at "No" time was there any talk / discussion / hints / tech tips / complaints from other technicians about problems with torque tubes/ Thrust Bearings / Flex Plates in the 928 series ( None at all ) or put another way = Zero
Now you would think if we had an issue with either Torque Tubes /Thrust bearings / Flex Plates in those 17 years I know full well it would of been discussed & there would of been plenty of paperwork in regards to in the field service remedy progammes , like there was with a whole range of technical gliches that all Porsche cars had back then , but there was " NO" discussion of problems with 928 Thrust bearings , T Tubes or flex plates .
This issue only started ( Thrust Bearing Wear )with the exact time period people using low oil film strength so called synthetic engine oils from the mid 1990's onwards & reaching its peak in the 2000's with people trying to understand it & blaming it on the poor old flex plate ( that you can bend in with one finger = some thrust ), but I can understand that because thats all they can see , you can not see the engine oil not keeping metal parts away from each other , that is too incremental too see & with all the advertising hype about so called synthetic oil at that time , most humans just fell for the advertising, thats what people do & i understand that
Thats why when I was at the Porsche service schools ( up to 1994 ) there was no mention of thrust bearing wear , the epoc of low oil film strength oils had not quite started ( in Australia) & the understanding of the destruction it dealt out is still being felt today
Thats why we see no thrust bearing wear at all ( Zero) even on 928S4's Auto's that we have never worked on before & we do a Thrust bearing measurment & we quickly find the engine thrust plate is pushed in to the max , front coupling inhex bolt a little loose , the rear inhex bolt a lot loose ( bolt stretch ) , but because this lucky 928S4 was on a 15w-50 or 20w-50 ( decent ZDDP ) there was no thrust bearing wear & the flex plate had been deflected in that state for some years , but no wear.
However the same year type 928S4 with much less flex plate deflection but had been on a 10W-40 or worse still a 5w-40 had **** loads of thrust bearing wear .
I can not change what I have seen , nor what I have experienced ,and be very carefull with so called explanations ( off the cuff ) from people who were never there at the time , meaning last century
Now lets get back to the real world here , I think you should know something , I working as a Porsche technician ( mechanic ) at major Porsche delership in Sydney Australia from 1977 to 1994 ( 17 years )
While there I ( in the 1980's ) went to 6 x week long Porsche Cars Australia ( Melb) Porsche technical schools ( usually one a year ) & in 1992 I was lucky enough to go to Germany to do a Porsche Tech school at the factory training facility & a hundred or so visits from Porsche in field servive engineers doing a one evening after work mini service school , now the reason I mentioned that is that at "No" time was there any talk / discussion / hints / tech tips / complaints from other technicians about problems with torque tubes/ Thrust Bearings / Flex Plates in the 928 series ( None at all ) or put another way = Zero
Now you would think if we had an issue with either Torque Tubes /Thrust bearings / Flex Plates in those 17 years I know full well it would of been discussed & there would of been plenty of paperwork in regards to in the field service remedy progammes , like there was with a whole range of technical gliches that all Porsche cars had back then , but there was " NO" discussion of problems with 928 Thrust bearings , T Tubes or flex plates .
This issue only started ( Thrust Bearing Wear )with the exact time period people using low oil film strength so called synthetic engine oils from the mid 1990's onwards & reaching its peak in the 2000's with people trying to understand it & blaming it on the poor old flex plate ( that you can bend in with one finger = some thrust ), but I can understand that because thats all they can see , you can not see the engine oil not keeping metal parts away from each other , that is too incremental too see & with all the advertising hype about so called synthetic oil at that time , most humans just fell for the advertising, thats what people do & i understand that
Thats why when I was at the Porsche service schools ( up to 1994 ) there was no mention of thrust bearing wear , the epoc of low oil film strength oils had not quite started ( in Australia) & the understanding of the destruction it dealt out is still being felt today
Thats why we see no thrust bearing wear at all ( Zero) even on 928S4's Auto's that we have never worked on before & we do a Thrust bearing measurment & we quickly find the engine thrust plate is pushed in to the max , front coupling inhex bolt a little loose , the rear inhex bolt a lot loose ( bolt stretch ) , but because this lucky 928S4 was on a 15w-50 or 20w-50 ( decent ZDDP ) there was no thrust bearing wear & the flex plate had been deflected in that state for some years , but no wear.
However the same year type 928S4 with much less flex plate deflection but had been on a 10W-40 or worse still a 5w-40 had **** loads of thrust bearing wear .
I can not change what I have seen , nor what I have experienced ,and be very carefull with so called explanations ( off the cuff ) from people who were never there at the time , meaning last century
03-13-2014, 04:06 PM
#48
Rennlist Member
Hi Fred – I’m guessing after using the red Loctite you put a dab of paint on the splines and that’s how you see if your clamp moved(?) I did red locktite/paint on splines thing to my car ~4 years ago and twice a year I check the paint mark to see if there’s been any movement. Knock on wood—none yet. Just curios if you do anything else like put a straight edge on the flywheel to see if it’s bowed or anything else. I feel like I should be doing more than just checking the paint mark on the splines.
The Loctite initally recommended for this duty was 260 although last time I used 270 due to availability. No idea if that is what you mean by Red loctite butthese formulations are in red bottles for what that is worth.
Indeed the idea is to mark the splines with white paint at the point they enter the hub so that you can easily spot any creep. I have got so complacent I do not check anything these days but then I know what to look for were it to let go- an inexplicable annoying vibration appears at 3050 rpm. I do visually check when I have the opportunity.
With a couple of mm of slip back in 1999 I could not visibly notice any bowing effect but you could see the hub jump when the bolt was released. I have seen several examples of TBF with the flexplate grossly deformed not to mention the totalled engine. Engine oil can only withstand so much thrust pressure before the white metal overheats and melts then it is all over- the white metal cools and sets and the engine is effectively seized. when this happened to the original thrust bearing in what is now my 928 GTS, I saw what they had to do to unseize the motor. After I purchased this 928 I stripped the motor and saw the damage to the crankcase webs that were cracked after the thrust bearing had spun. Diffferent oils may well have put up differing levels of resistance but doubtless the end result would have been the same.
Regards
Fred
03-13-2014, 05:03 PM
#49
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Hi Erkka , thats interesting about some mechanics putting stuff in the wrong order ( what on earth does that mean ? ) & how on earth can one get it wrong ? , & the so called Porsche official line ( never seen that in writing ) & if in writing it must be from the period of these cars & not from some desk jocky in this century who is just clutching at anything ,& where did you hear that 3rd hand incorrect info/ myth from anyway ? .
Now lets get back to the real world here , I think you should know something , I working as a Porsche technician ( mechanic ) at major Porsche delership in Sydney Australia from 1977 to 1994 ( 17 years )
While there I ( in the 1980's ) went to 6 x week long Porsche Cars Australia ( Melb) Porsche technical schools ( usually one a year ) & in 1992 I was lucky enough to go to Germany to do a Porsche Tech school at the factory training facility & a hundred or so visits from Porsche in field servive engineers doing a one evening after work mini service school , now the reason I mentioned that is that at "No" time was there any talk / discussion / hints / tech tips / complaints from other technicians about problems with torque tubes/ Thrust Bearings / Flex Plates in the 928 series ( None at all ) or put another way = Zero
While there I ( in the 1980's ) went to 6 x week long Porsche Cars Australia ( Melb) Porsche technical schools ( usually one a year ) & in 1992 I was lucky enough to go to Germany to do a Porsche Tech school at the factory training facility & a hundred or so visits from Porsche in field servive engineers doing a one evening after work mini service school , now the reason I mentioned that is that at "No" time was there any talk / discussion / hints / tech tips / complaints from other technicians about problems with torque tubes/ Thrust Bearings / Flex Plates in the 928 series ( None at all ) or put another way = Zero
03-13-2014, 06:14 PM
#50
Under the Lift
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I'm trying to understand how the rear clamp movement would work to load up the front flexplate as much as I have seen if as you maintain the front clamp doesn't move. That would require the TT shaft to move forward.
The rear end of the TT shaft is spec'd to be 2mm beyond the rear end of the TT (Dimension A in image below). Note the groove in the shaft, hardly bigger than the bolt that must pass through it. I've had my TT shaft out several times over the years, never moving the TT shaft myself (bearings are original), and the shaft is just where it is supposed to be. My TT shaft doesn't slip through the carriers easily like many others do. If the rear clamp had been the one to move, the bolt would no longer line up with the access hole in the TT.
Since the rear clamp/shaft mechanism is restrained by narrow cutouts in the torque converter snout (second picture below) and the shaft, to accumulate 2-3 or as much as 10-15mm of preload on the front flexplate without any front clamp movement would require the TT shaft itself to move forward that amount, necessitating significant damage to the rear shaft slot, torque converter snout slot or bolt to do that and resulting in visible misalignment through the TT access hole. The TT shaft, TC snout and bolt are relatively locked in position by locating slots.
Your proposal that the rear clamp is moving, not the front, just doesn't go along with any of the dozens of S4 automatic TT's I have worked on or 15 years or seeing what has gone on in my 89 S4. The before and after pictures shown here are characteristic. Just because the splines don't show any "polishing" doesn't mean it isn't moving or that the photos here were misrepresented as before and after.
So, is the shaft moving forward 2-3 or as much as 10-15mm? And how does it do that repeatedly after releasing and repositioning the front clamp, relieving the preload without the shaft position changing relative to landmarks on the inside of the bellhousing? If you put a paint mark on the shaft adjacent to the bellhousing casting for the mounting of the clutch guide tube (when used in the manual cars), forward movement should be obvious and measurable.
We must have some very basic misunderstanding or miscommunication going on here.
The rear end of the TT shaft is spec'd to be 2mm beyond the rear end of the TT (Dimension A in image below). Note the groove in the shaft, hardly bigger than the bolt that must pass through it. I've had my TT shaft out several times over the years, never moving the TT shaft myself (bearings are original), and the shaft is just where it is supposed to be. My TT shaft doesn't slip through the carriers easily like many others do. If the rear clamp had been the one to move, the bolt would no longer line up with the access hole in the TT.
Since the rear clamp/shaft mechanism is restrained by narrow cutouts in the torque converter snout (second picture below) and the shaft, to accumulate 2-3 or as much as 10-15mm of preload on the front flexplate without any front clamp movement would require the TT shaft itself to move forward that amount, necessitating significant damage to the rear shaft slot, torque converter snout slot or bolt to do that and resulting in visible misalignment through the TT access hole. The TT shaft, TC snout and bolt are relatively locked in position by locating slots.
Your proposal that the rear clamp is moving, not the front, just doesn't go along with any of the dozens of S4 automatic TT's I have worked on or 15 years or seeing what has gone on in my 89 S4. The before and after pictures shown here are characteristic. Just because the splines don't show any "polishing" doesn't mean it isn't moving or that the photos here were misrepresented as before and after.
So, is the shaft moving forward 2-3 or as much as 10-15mm? And how does it do that repeatedly after releasing and repositioning the front clamp, relieving the preload without the shaft position changing relative to landmarks on the inside of the bellhousing? If you put a paint mark on the shaft adjacent to the bellhousing casting for the mounting of the clutch guide tube (when used in the manual cars), forward movement should be obvious and measurable.
We must have some very basic misunderstanding or miscommunication going on here.
03-13-2014, 06:52 PM
#51
Drifting
Thrust bearing wear & engine oil are interlocked far more than you realise , here are some Rennlist threads on thrust bearing wear on the other Porsche's & yes they were destroying crankcases because of it , just like the 928 when the engine oil film strength of the low viscosity low ZDDP engine oil was used
Look at post number "4 " ( Steve Weiner Rennsport Systems ) , this is regard to Porsche 993 Turbo & 996 Turbo Thrust Bearing wear ......
https://rennlist.com/forums/5669871-post4.html
On this thread look at post no "359 "( Steve Weiner Rennsport Systems ) , again about engine oil & thrust bearing wear in this case with 993 Porsche's & low oil film strength oils ...................
https://rennlist.com/forums/5800824-post359.html
Look at post number "4 " ( Steve Weiner Rennsport Systems ) , this is regard to Porsche 993 Turbo & 996 Turbo Thrust Bearing wear ......
https://rennlist.com/forums/5669871-post4.html
On this thread look at post no "359 "( Steve Weiner Rennsport Systems ) , again about engine oil & thrust bearing wear in this case with 993 Porsche's & low oil film strength oils ...................
https://rennlist.com/forums/5800824-post359.html
03-13-2014, 07:11 PM
#52
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Thrust bearing wear & engine oil are interlocked far more than you realise , here are some Rennlist threads on thrust bearing wear on the other Porsche's & yes they were destroying crankcases because of it , just like the 928 when the engine oil film strength of the low viscosity low ZDDP engine oil was used
03-13-2014, 07:20 PM
#53
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This is a very well traveled road and no new information or ideas so far to explain the TBF problem of the automatic 928s, other than the obvious drive shaft pullout at the front flex plate due to drive shaft wind up under torque load.
No magic oil blend will help this problem nor will tightening the rear pinch bolt or designing a new rear clamp.
No magic oil blend will help this problem nor will tightening the rear pinch bolt or designing a new rear clamp.
03-13-2014, 07:28 PM
#54
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the only comment i would add and i dont know the answer is when you look at "crankwalks" on various types of engines especially japanese cars like mitsubishi i believe they talk about one engine type that walks all the time, it is always with manuals and not automatics.
in our case, we always talk about autos crankwalking.
it would be interesting to look at why crankwalks occur across a wide of manufacturers and transmission types.
in our case, we always talk about autos crankwalking.
it would be interesting to look at why crankwalks occur across a wide of manufacturers and transmission types.
03-14-2014, 04:54 AM
#56
Drifting
We have had no 928S4 /GTS Thrust bearing wear at all over the last twenty years ( 20 years ) if they had been on a 15w-50 or 20w-50 , no matter how much flex plate deflection they have
But we have had to repair plenty of thrust bearing ( excessive wear / beyond tolerance ) & worse , be it on 928s / S4 / GTS / 944S2 / 968 that had all been on low viscosity low oil film strength oils , like 5w-40 & some 10w-40 oils , but never 20w-50
I can not see any other explanation to what we experience & its completely preventable , hence the time & trouble I have gone to
No complaints from me on the unnecessary wear( brings in a lot more repairs & money ) , just so long as I warn people of what I experience from working on Porsche's for the past 37 years
PS , and when you realise ( penny drops) of what I have been warning about , do drop me an email
But we have had to repair plenty of thrust bearing ( excessive wear / beyond tolerance ) & worse , be it on 928s / S4 / GTS / 944S2 / 968 that had all been on low viscosity low oil film strength oils , like 5w-40 & some 10w-40 oils , but never 20w-50
I can not see any other explanation to what we experience & its completely preventable , hence the time & trouble I have gone to
No complaints from me on the unnecessary wear( brings in a lot more repairs & money ) , just so long as I warn people of what I experience from working on Porsche's for the past 37 years
PS , and when you realise ( penny drops) of what I have been warning about , do drop me an email
03-14-2014, 07:01 AM
#57
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Hi Bruce,
Well if you don't advise your clients about the 928 automatics' drive shaft pullout out issue at the front flex plate, you will guarantee yourself some more TBF engine work. As others have said on this thread, oil viscosity will not protect the engine from this kind of problem.
About the "penny drops," same for you with what we have been trying to tell you about what we have been seeing for years.
Cheers,
Well if you don't advise your clients about the 928 automatics' drive shaft pullout out issue at the front flex plate, you will guarantee yourself some more TBF engine work. As others have said on this thread, oil viscosity will not protect the engine from this kind of problem.
About the "penny drops," same for you with what we have been trying to tell you about what we have been seeing for years.
Cheers,
03-14-2014, 07:28 AM
#58
Drifting
Au Contraire dear Constatine ( if thats your'e name because I am not sure ? ) , we do not have 928 thrust bearing issues at all with the use of 20w-50 enine oils with decent levels of ZDDP ( you must get out into the world more ),nor do we have T Tube issues at our workshop because we figured it out years ( decades) ago & I can not believe for the life of me you could not do the same , its so simple .
If you read what I stated you will see that the oil film strength is the issue with thrust bearings ( which you must realise by reading what Steve Weiner from Rennsport Systems ( fellow USA citizen ) has found the same as I ( link that I gave) at least I hoped you at least looked at it ? ,
Why are you so worried about me stating my 37 years experience ?, I am not selling anything , is that your'e worry
If you read what I stated you will see that the oil film strength is the issue with thrust bearings ( which you must realise by reading what Steve Weiner from Rennsport Systems ( fellow USA citizen ) has found the same as I ( link that I gave) at least I hoped you at least looked at it ? ,
Why are you so worried about me stating my 37 years experience ?, I am not selling anything , is that your'e worry
03-14-2014, 09:08 AM
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Hi Bruce,
Now you are getting a bit personal. Have I attacked you personally?
Yes that's my name and I have been around the world quite a bit. We also did not R&D the Super Clamp in our basement closet.
Truthfully we haven't made enough on our Super Clamps to even cover our initial R&D into this problem and it's development. We keep them on the shelf since people believe in them and want them. In fact, another vendor tried to rip off the design when we wanted to stop selling them at one point, so we stood them up again.
I am extremely confident in our research and it's findings about the root cause of most TBF incidents in 928s equipped with automatics, as well as our solution to stop this problem.
Apologies that our findings do not support your oil theory.
As far as you not selling anything, does that mean you do TBF'd 928 engine rebuilds for free?
Cheers,
Now you are getting a bit personal. Have I attacked you personally?
Yes that's my name and I have been around the world quite a bit. We also did not R&D the Super Clamp in our basement closet.
Truthfully we haven't made enough on our Super Clamps to even cover our initial R&D into this problem and it's development. We keep them on the shelf since people believe in them and want them. In fact, another vendor tried to rip off the design when we wanted to stop selling them at one point, so we stood them up again.
I am extremely confident in our research and it's findings about the root cause of most TBF incidents in 928s equipped with automatics, as well as our solution to stop this problem.
Apologies that our findings do not support your oil theory.
As far as you not selling anything, does that mean you do TBF'd 928 engine rebuilds for free?
Cheers,
Last edited by Black Sea RD; 03-14-2014 at 09:43 AM. Reason: Threw in a dig about the engine rebuild.
03-14-2014, 10:23 AM
#60
"Tribology" has the answer to why there is thrust bearing failures with the forward migration of the forward clamp due to torque "wind" up on the auto 928s. Tribology is the study of lubrication and friction.
Unfortunately the design of the thrust bearing used in our cars is the most primitive design of any thrust bearing especially when the oil film breaks down due to pressure and boundary lubrication (friction increases) which causes heat generation and further oil film degeneration.
AGM Michell developed canting kidney shaped segments abutting up against wedge of oil film between the segments and the collar. This type of thrust bearing are used in all ships even in ships developing over 70,000 ps on a single shaft and they have been used in ships that have developed over 250,000 shaft HP on multiple shafts, with very few failure since their introduction in the early 1900s. All propeller driven ships are today fitted with this type of bearing.
Torque wind up of propeller shafts is used to measure the horsepower absorbed by the propeller/s, so wind up is a common know phenomena.
In closing do you know why Queensland's name their most popular beer "XXXX" (4 X)? Because they cannot spell beer.
Unfortunately the design of the thrust bearing used in our cars is the most primitive design of any thrust bearing especially when the oil film breaks down due to pressure and boundary lubrication (friction increases) which causes heat generation and further oil film degeneration.
AGM Michell developed canting kidney shaped segments abutting up against wedge of oil film between the segments and the collar. This type of thrust bearing are used in all ships even in ships developing over 70,000 ps on a single shaft and they have been used in ships that have developed over 250,000 shaft HP on multiple shafts, with very few failure since their introduction in the early 1900s. All propeller driven ships are today fitted with this type of bearing.
Torque wind up of propeller shafts is used to measure the horsepower absorbed by the propeller/s, so wind up is a common know phenomena.
In closing do you know why Queensland's name their most popular beer "XXXX" (4 X)? Because they cannot spell beer.