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I will also have the oil change done to see the condition of the oil itself and pray that the drain plug isn't gunked up as I hear that is a tell tale sign of TBF
Checking the end play of the crank is the only way to know, and is easy for any mechanic to do.
I'm in the camp that feels the TBF issue is grossly overblown. Yes it's something to be aware of and should to be checked on every 87+ automatic 928 prior to purchase. If everything checks out, apply one of the known fixes and don't loose sleep over it.
Others have added a second clamp similar to the stock one, lictite etc...
Originally Posted by kamaro
I'm not sure from where you guys are getting your prices, but $20K for intake refresh? .. that's McLaren F1 price scheme right there!
If this thread goes on too much longer on the intake refresh conversation, such a job will eventually include a full engine rebuild and a transmission overhaul.
Checking the end play of the crank is the only way to know, and is easy for any mechanic to do.
I'm in the camp that feels the TBF issue is grossly overblown. Yes it's something to be aware of and should to be checked on every 87+ automatic 928 prior to purchase. If everything checks out, apply one of the known fixes and don't loose sleep over it.
Others have added a second clamp similar to the stock one, lictite etc...
If this thread goes on too much longer on the intake refresh conversation, such a job will eventually include a full engine rebuild and a transmission overhaul.
I appreciate the positivity and the links to those two solutions
Being new to the Porsche Platform, I am learning a lot
I will likely opt for the Ritech clamp since it can be fitted without removing the Torque Tube which means labor hours $aved
I am not even thinking about the intake refresh as I just want to ensure this TBF issue is dealt with first
Should I also replace the two bolts on both ends?
I went to the shop today, they got it up on the hoist and changed the oil (no metal in the oil and the drain plug was clean).
They looked into both ends to inspect with a camera instead of taking everything apart just to save some time and have the RENNLIST community guide further
I brought the car home and will take it back next week
Here is what I saw on the front end... a lot of splines, I haven't come across a single video where there is this much spline showing?
The shop suggests the bolts have definitely been played with before as the front port hole didn't have the rubber boot on it and the rear bolt shows signs of stripping
All the videos of this issue online show very small amount of splines... so I'm worried after seeing that much spline in my car. Pictures below are from other people's cars on Youtube
The position of the transaxle shaft is wrong and needs to be positioned correctly! The shaft has been installed wrong and is most likely pushing against the flexplate of the torque converter. The pinch bolt at the transmission sits in a groove if everything is well. I don't know how they managed it, but to insert the bolt requires some force due to the lack of groove (hammer).
Bottom line: both pinch bolts have to come out and the whole shaft has to move forward in direction to the motor. It might be a challenge with everything in place. Rennlist will advice you here, I'm sure. Here is a picture of the rear pinch bolt and clamp assembly. Normally the transaxle shaft sits up to the point where you see the small round hole. Your's is pushed easy beyond that point and rests (most likely) against the TC flexplate. Here's a picture of my GTS after a I fixed my TC bearings and with a new transaxle from 928 international. Photo was taken with all parts adjusted to factory spec. and TB @ 0.25 mm. After this Loctite 290 was applied, because back than the was no other cost effective solution. Mileage was about 100 k in 2005, today at 186 k with no change in TB tolerance. Meanwhile the car has been equipped with a Ritech clamp. Works great and ready to remove. They're would be no way to install it and I hope you understand why. Picture shows half of the clamp for illustration how it works.
The only logical explanation for that dog's breakfast is that some chump did something unbelievably inept. It is not difficult to move the shaft axially either by accident or intent.
The 87 S4 was fitted with the 25mm shaft and the only way they could get a bolt in that is not Indexed correctly would be to push the shaft in the direction of the torque converter so that the bolt is no longer inserted in the splined area. The consequence of this would be the splines sitting well outboard of the clamp as seen in the photo. The problem is the amount of splined shaft being pinched must be nigh on zero and that assumes such is even possible at the torque converter end. Not even Thor could hammer the bolt over those splines without causing huge shaft damage.
Way too many engines have been trashed by TBF not to mention the 28mm diameter shafts that have sheared. Unfortunately there is no data base in the public domain to understand just how prevalent this issue is . My 90S4 was the joint first example to have a mitigation applied and the Loctite procedure is still holding 25 years on . The fretting corrosion that seemingly causes this problem is what it is.
You need to have 2 new pinch bolts on hand before the car goes back to have a proper flex plate inspection performed.
The shaft is not properly positioned if it’s the correct shaft,
it’s way to far to the rear.
OR the wrong shaft was installed that is too short.
I suggest not run the engine any more than necessary till the front pinch bolt has been removed and the thrust clearance has been checked.
NOTE the rear pinch bolt must be removed, then the driveshaft cutout must be centered in the rear input shaft before the rear bolt is reinstalled.
NOTE if the rear portion of the driveshaft is centered in the bolt cutout,
then its quite possible that the wrong driveshaft has been installed,
I have never seen this much splines come out of the front clamp.
If you have the wrong shaft then the TT and trans should be dropped,
and the TT have the correct driveshaft installed and the bearings replaced.
NOTE post the crank endplay.
NOTE have them watch the endplay check video from frenzie before they work on your car.
Just get them resituated and check end play. Usually the shaft walks forward. Not sure why it looks like someone moved all the way back. Once both bolts are loose you can scoot it. You may want to replace the bolts.
You need to have 2 new pinch bolts on hand before the car goes back to have a proper flex plate inspection performed.
The shaft is not properly positioned if it’s the correct shaft,
it’s way to far to the rear.
OR the wrong shaft was installed that is too short.
I suggest not run the engine any more than necessary till the front pinch bolt has been removed and the thrust clearance has been checked.
NOTE the rear pinch bolt must be removed, then the driveshaft cutout must be centered in the rear input shaft before the rear bolt is reinstalled.
NOTE if the rear portion of the driveshaft is centered in the bolt cutout,
then its quite possible that the wrong driveshaft has been installed,
I have never seen this much splines come out of the front clamp.
If you have the wrong shaft then the TT and trans should be dropped,
and the TT have the correct driveshaft installed and the bearings replaced.
NOTE post the crank endplay.
NOTE have them watch the endplay check video from frenzie before they work on your car.
I had a feeling the splines were too long... so this confirms my fear
I wonder how the car has managed to run all this time with this setup being so wrong
I will look online for the bolts and order them, the shop didn't want to loosen them given that they didn't have new bolts to install
How much work would you say the above is in terms of labor hours? This sounds like it will add up quickly!
The position of the transaxle shaft is wrong and needs to be positioned correctly! The shaft has been installed wrong and is most likely pushing against the flexplate of the torque converter. The pinch bolt at the transmission sits in a groove if everything is well. I don't know how they managed it, but to insert the bolt requires some force due to the lack of groove (hammer).
Bottom line: both pinch bolts have to come out and the whole shaft has to move forward in direction to the motor. It might be a challenge with everything in place. Rennlist will advice you here, I'm sure. Here is a picture of the rear pinch bolt and clamp assembly. Normally the transaxle shaft sits up to the point where you see the small round hole. Your's is pushed easy beyond that point and rests (most likely) against the TC flexplate. Here's a picture of my GTS after a I fixed my TC bearings and with a new transaxle from 928 international. Photo was taken with all parts adjusted to factory spec. and TB @ 0.25 mm. After this Loctite 290 was applied, because back than the was no other cost effective solution. Mileage was about 100 k in 2005, today at 186 k with no change in TB tolerance. Meanwhile the car has been equipped with a Ritech clamp. Works great and ready to remove. They're would be no way to install it and I hope you understand why. Picture shows half of the clamp for illustration how it works.
Thank you for this detailed reply.
The shop did note that flexplate has pressure on it so I guess that's no surprise
I assume I cannot use a Ritech clamp based on the shaft being installed incorrectly?
order new bolts either from the dealer,
or from Roger he has them in stock .
NOTE these are hi strength bolts 12.9
dont buy one from Home Depot,
it will shear off or the head will strip out.
To drop the TT/ transaxle will be about 6 hours,
to replace the TT maybe another 2 hrs,
then reinstall it .
NOTE if the shaft is too short,
I would consider either 928 INTL for a stock rebuild unit,
or Blacksea for a fresh TT with new super bearings and a new driveshaft.
NOTE the driveshaft doesnt really need a clamp until you determine if its walking.
Once a proper inspection has been performed and both the front and rear pinch bolts have been tightened ,
then the car put into service and then a subsequent inspection made after 5 K miles , and movement found,
thats when you will know if a clamp could be used.
NOTE you can only clamp one end of the driveshaft,
in reality both ends should be clamped to prevent the shaft from migrating in either clamp.
order new bolts either from the dealer,
or from Roger he has them in stock .
To drop the TT/ transaxle will be about 6 hours,
to replace the TT maybe another 2 hrs,
then reinstall it .
NOTE if the shaft is too short,
I would consider either 928 INTL for a stock rebuild unit,
or Blacksea for a fresh TT with new super bearings and a new driveshaft.
Is there a part number anywhere on the shaft to know if its incorrect / too short? Or any way to inspect using a camera through port hole?
I would like to tackle this problem in a way that makes the most sense financially and mechanically
I assume the shaft is from another model as there is no other way to make sense of how else there would be so much spline showing on the front end?
Is there a solution whereby I would no longer need to worry about checking for endplay every year as most suggest?
Looks like my first Porsche is going to be a handful but I'm thankful to you and the rest of Rennlist for your advice / guidance!
Also today upon cold start, the car idled itself slowly up to around 2100RPM like I was holding the throttle... I shut it off after about a minute and turned it back on and the idle was back down to normal range.
Usually my older Mercedes would do this when the idle control valve was faulty / dirty etc. I am wondering if the 928s suffer from a similar issue?
02-27-2024, 12:14 PM
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