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bent torque tube axle

 
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Joined: 18 Mar 2017
Posts: 631
Location: Sweden

PostPosted: Wed Aug 28, 2024 4:52 pm    Post subject: bent torque tube axle Reply with quote

I'm restoring a 931 car that is mostly in pieces right now. I checked the torque tube after re-rusting and painting it.
I noticed that its slightly bent on the engine side, the bearing doesn't sound very nice either.

I didn't notice anything when I drove the car before picking it apart, but I didn't drive it very much.

Shouldn't it have been obvious?

Has anyone straitened one?

I think it would be possible to unbend it in a press if removed.
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morghen  



Joined: 21 Jan 2005
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PostPosted: Wed Aug 28, 2024 5:07 pm    Post subject: Reply with quote

How much is it bent? Maybe it got bent during disassembly?
You can try to bend it back i guess...it may wear the needle bearing sooner if its not straight.
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Joined: 18 Mar 2017
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PostPosted: Wed Aug 28, 2024 5:25 pm    Post subject: Reply with quote

morghen wrote:
How much is it bent? Maybe it got bent during disassembly?
You can try to bend it back i guess...it may wear the needle bearing sooner if its not straight.



Haven't measured it yet, 1-2 mm maybe at the tip. Its enough rotate back to its preferred resting place if I turn it 90 degrees.
Other TT I have are dead straight.

It could have been bent on disassembly. If I had to guess I would think that the shaft would be of pretty flexible steel and be hard to bend...
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morghen  



Joined: 21 Jan 2005
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PostPosted: Wed Aug 28, 2024 9:00 pm    Post subject: Reply with quote

maybe the shaft isnt bent but the bearings sleeves are deformed/crunched and the shaft sits at an angle ?
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PostPosted: Wed Aug 28, 2024 9:09 pm    Post subject: Reply with quote

I think I have to pull out the shaft and have a look.
Probably need to replace at least one of the bearings.
From experience with my NA TT, the end bearings are probably the worst.
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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Thu Aug 29, 2024 7:10 am    Post subject: Reply with quote

I'm wondering if the closest bearing is in the wrong position which allowed it to get bent? Like that unsupported section is now longer? This seems weird to me that it would get bent (see my final note below too)

I'll watching for what you find for sure

What I can tell you is that the tubes themselves have some bend to them. All that have been checked so far especially the longer S2 versions (Audi). One of my pet theory's on the carrier design was that it deforms to the position its at on first install as new. In this way the shaft stays as straight as possible (carriers are sheet metal). Its also why I think they used C5 clearance bearings, not C or C3 which are much more common. The deformation in the tube actually preloaded the bearing (common practice) or else why would there be C5 (more clearance)? Those bearings have to hate being spun up when cold especially on really cold days. I want preload of some kind on any bearing. Better for the bearing

These are the kind of thoughts I had when working the Alum tube project and why I know the tubes are typically bent (lots of testing). Some more than others. My thought there was that Porsche could just take raw tube straight from shelf and use it without much processing

also a bad bearing can cause you to think a shaft is bent. I see this almost every day in my work life. The farther away from that bad bearing only makes it seem worse
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PostPosted: Mon Oct 14, 2024 7:14 pm    Post subject: Reply with quote

Small update.
I removed the axle from the tube, at first glance it doesn't appear to be bent. I'm waiting for a pair of v-blocks to be able to check it.
But it seams ridiculous that a 25 mm / 1 inch shaft will take a bend, I would also guess that its made from some kind of hard and "springy" steel making it even more unprobable.

I will remove the 1st bearing in the tube to check that out. Making a special tool to extract that...
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Nobbi  



Joined: 24 Aug 2006
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PostPosted: Sun Oct 20, 2024 7:54 pm    Post subject: Reply with quote

Bending the drive line happens when the car gets lifted under the gearbox.Even more, the older your rubber on the attachment of the gearbox is.So, never lift the car there, even when its really handy...

Nobbi
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barnwerks  



Joined: 28 Oct 2022
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PostPosted: Sun Oct 20, 2024 10:25 pm    Post subject: Reply with quote

In regard to bending the driveshaft, I will contend that, while there can be potential for damage to the transaxle or it's mountings, lifting the car from the transaxle will not introduce unusual forces to the driveshaft or support tube.
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PostPosted: Mon Oct 21, 2024 7:40 am    Post subject: Reply with quote

Made a contraption to hook onto the first bearing and pull it out.




Yes, the bearing was crusty and sloppy...

Looks like I can save the inner plastic bushing and the the outer carrier too. Just need to find the right bearing.
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Raize  



Joined: 18 Sep 2013
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PostPosted: Mon Nov 04, 2024 4:43 am    Post subject: Reply with quote

I remember reading a post once that the tolerance class of that bearing is extremely important and you need the tightest-tolerance version but I just can't find it...
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PostPosted: Mon Nov 04, 2024 4:47 am    Post subject: Reply with quote

Raize wrote:
I remember reading a post once that the tolerance class of that bearing is extremely important and you need the tightest-tolerance version but I just can't find it...


Not the tightest, the loosest, C5. 6006 2z c5

But it seems that bearings of standard tightness have been used as replacement by some. I think the bearings I got for my NA is C0, standard.
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Porsche 931 -79
Porsche 911 -77, 3.2 Targa
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