Mark R.

I wonder why they chose not to weld the rear clamp in place. That seems odd to me...

In order to function, it must be aligned with the cutout in the sleeve, so there's only one location for it to sit.

And it seems like welding it in that one location would make it a much more robust design.

It would better support the side load on the bolt, and make it overall less sensitive to the bolt torque.

The shaft would still be the weak link, but at least it would eliminate any elongation of the sleeve cutout.

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touay001

No, the one on the right is. The photos are not that clear. The shaft and clamp look much better than the photos. I can't for the life of me find the charger for the camera. The photos were taken be my phone with 4X zoom and out of focus.

JET951

Looking at the photos you took , one with flash and one without , it looks ( from what I can see ) like there is quite a bit of spline "worn away" damage to the shaft half moon cut out area , naturally this wear only occurs when the shaft has migrated forward

The reason I asked about the bolts is that the bolt on the right looks newer than the one on the left , is there any red paint on the in-hex area of the bolt head of any of the two bolts ( not that it matters much ) , because over the decades the rear bolt mainly gets replaced far more often than the front , with things like transmission removal etc etc etc

Oh , by the way , there is( what looks like ) rust powder all around the T Tube inspection hole , its just wet with oil & , you can see it again with the flash , but this time the "flash " picture gives it a different colour in that photo

FredR

Bruce,

This is what I suspected I was looking at but was hoping I might just be wrong. The thing that threw me a bit was the condition of the bolt, more specifically the shank which looks very clean to me with no tell tale signs of it having been hammered as in Dave's earlier pic- possibly explained by an earlier event wherein the bolt was replaced Buchanan style. If so, my logic tells me that the new bolt was holding but only after it had slid forward and could go no further. Thus when the rear bolt was released the assembly was able to move back the "magic" 2mm.

Is this a reasonable prognosis?

Rgds

Fred

touay001

Thanks guys. I appreciate your help. I was planning on replacing the torque tube bearing sometime in the near future. There is no noise or rattle coming from the TT but, I have this whining noise at idle since I got the car in 2003. It only whines at idle and as soon as I put it into gear the whine disappears. I have read a few posts about the issue and I have posted locally (landshark) and there was an opinion that it was the hydrolic lines that causes this whining noise. It also seems that Porsche had introduced a hydrolic hose with a loop in order to resolve this issue. Some other opinions suggests it is the oil pump. Another issue that I have with the trans is, if I don't drive the car for more than a week, the trans will leak fluid (large amount). There are other members that have the same issue as well. Anyway, I was planning on resolving these issues and while at it I was going to replace the TT bearings with the super bearings from Constantine. I have also bought another transmission as a spare in case it is something within the trans.

JET951

Thats the auto trans oil pump Akram , in the past that transmission had been allowed to run very low on auto oil ( its called neglect ) & its very slightly damaged the oil pump gears causing that noise you described at idle in Park or Neutral , however when you put it in gear ( D ) the oil pressure between the gear teeth minimises/ masks it quite a bit ( it actually doesn't go away completely ), its a bit like ( a lot like actually ) when somebody runs a 928 ( any ) power steering pump way too low on oil but doesn't care and just keeps driving it with a screaming P /steer pump & finally when the power steering oil leak is fixed & the oil level is now fine , the power steering pump is noisy & will not go away ( same principle, damaged gears in the pump )

And no, I do not know you're car , but we have a few 928S/S4's that in a previous life have had leaking auto trans & they had been allowed to run very very very very very low on auto oil( by previous owners ) & it damages the oil pump gears , hence you can hear that noise that goes away in gear , but i suspect you already know that

JET951

Hi Fred , yes , you are correct , but we ( all of us ) do not know the history of this particular 928S4 , the index bolt is probably just a couple of years old , the bolt before this one was probably very badly ( teeth damaged " on its flank , who knows , who cares

In the end its really makes no difference at all , all we have to do is maintain these poor cars that are getting older & at different levels of neglect

Oh , by the way Fred , on the other 928 Rennlist thread " clutch to floor 5,000 after new parts " by Rob Roy ,Ken ( Rob Roy ) has put a photo up of his 928 manual( clutch area) & the T Tube shaft has migrated way too far forward ( another one )

Regards
Bruce B

FredR

Bruce,

I see that Akram is in your neck of the woods - given the dialogue to date It would seem a good idea if he can get the car to you for a "real world assessment" of where to go next. if that is not possible maybe he can "throw a shrimp on the barbie" to tempt you boys to his neighbourhood so that you take a butchers at the thing.

Kind of sounds as though this is not going to be a single problem and now he needs an assessment as to the viability of the shaft splines in situ as it were yet alone the possibilities.

Great cars when they are running properly but "trouble free" and "cheap to run" rarely apply to the 928 [ or any exotic] sad to say.

Rgds

Fred

Mark R.

I'm sure you guys know, the front side of that split sleeve is tapered.

So doesn't he need to be careful not to let that clamp move any further forward, or it may slide right off the sleeve?

And I'm guessing it would be pretty difficult to get it back in place while working through that small access hole...

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G.P.

It's ok to slide the clamp forward off the sleeve to inspect the sleeve for cracks. After doing this the clamp can be retrieved with a magnet. It can be a bit fiddly, but there is no problem.
That is my experience after discussion with Bruce on my manual. I have not worked on a auto but I suspect it's similar. Hopefully someone can confirm this.

touay001

It should be alright. I have moved it back and forth on the hub. There is resistance to slide off the hub.

928Myles

Following up on the issues of:
1 - The M10 bolt stretching over time thereby letting the clamp move, and
2 - The 2mm of longitudinal slack in the groove.

Given that there appears to be 2mm horizontal slack in the system with the bolt in place (but not tight) is their enough room to cut new threads in the clamp and put in a M12 bolt instead?

Looking at the photo's above it would appear that there might be enough room to drill out the clamp and outer sleeve (without affecting the drive shaft) to fit a larger bolt.

This would provide a stronger bolt with more resistance to stretch that also filled the half moon groove in the driveshaft more fully. In conjunction with an upgraded front clamp and the flex plate on an auto, would this solve the issue or just transfer the problem to somewhere else in the drivetrain?

( I have a set of super bearings and clamp to install at some stage so could re-cut the threads with everything apart and easy to get to).

Myles

Vilhuer

Because how setup is put together. Bearing needs to go in from the front and welded clamp would be in the way.

Dave928S

^^ Welding heat/stress would badly affect that gearbox 5th gear input shaft in any case.

Myles ... only precise measurements would give you the answer as to whether a 12mm bolt would still have some needed clearance from the shaft cut out, but I can't think of a downside, as it would allow you to increase the clamping force.

Mark R.

Ahh... Yes. That makes sense. I knew there had to be a good reason. Thanks!

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