[Cloud9...68]

... even with the pinch bolt fully torqued?



I've got the engine in (finally) and am starting the long process of connecting everything up, and I've noticed something that strikes me as strange. The clutch input shaft (referred to as the "central shaft I" in the manual) fits beautifully into splines of the disk, and when I slide it so that its nose mates against the pilot bearing, the clamping sleeve's pinch bolt is nicely centered in the window in the torque tube:



   



The rear clamping sleeve is in place, with the pinch bolts tightened down, and the front pinch bolts of the rear clamping sleeve are likewise well centered in the rear torque tube window:



   



The thing that strikes me as odd is that with relatively little effort, using a large-ish screwdriver, I can move the front clamping sleeve back, such that (I assume) it's nose is no longer pressing against the pilot bearing. Again, this is with the pinch bolt in place and fully torqued. When I move the front clamping sleeve back, the rear clamping sleeve does not move; it stays in exactly the same position in its window. I can't do the same thing with the rear clamping sleeve - no amount of prying with a pry bar can get it to move.



Also, I confirmed that the front clamping sleeve is not moving relative to the drive shaft (as expected, given that the pinch bolt is engaged). When I move the front clamping sleeve backwards with the screwdriver, I can see the splines of the drive shaft move back with it.



I thought the drive shaft was a single piece, but it's acting as though it has a separate piece in the front, which can move fore and aft independent of the rear part of the shaft.



My concern is that I would think the nose of the clamping sleeve should be snugly seated against the pilot bearing at all times, but on my car, this doesn't seem to be the case, as there doesn't seem to be anything to keep the input shaft pressed against the pilot bearing. Is this normal, or is it something I should be concerned about? Thanks.

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[Cloud9...68]

That makes sense, based on my observations. But what concerns me a little is that there doesn't appear to be any mechanism by which forward pressure is exerted on the front part of the shaft to ensure the input shaft remains firmly seated against the pilot bearing. In other words, it seems like it's free to "wander" backwards, which seems very strange. I'm probably being overly anal, but this is by far the most ambitious car project I've ever undertaken, and I want to make sure (as I can be, anyway) that there aren't any preventable anomalies that are going to lead to bangs, clunks, smoke, or other nasties.

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[flash]

it does not need to be seated agains the bearing. it only need to be inserted into it.



that being said, i can't remember if it moved or not. i will be up at my car tomorrow and will look.

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[Cloud9...68]

[quote name='flash' timestamp='1334716909' post='125429']

it does not need to be seated against the bearing. it only need to be inserted into it.

[/quote]



I suppose that makes sense. It's kind of a long story (and not really relevant) why I tried to see if the input shaft moved backwards with the pinch bolt attached, so more than likely this isn't something most people would routinely check. I was just surprised that it moves at all, and how relatively easily. One thing I don't know is how far back it moves, because I didn't want to move it to where the clamping sleeve was far enough back in the torque tube window that I wouldn't be able to get a screwdriver on it to move it back. Not knowing how the torque tube/drive shaft assembly is put together, I was concerned that one reason the input shaft can be moved is because the torque tube bearings, which I assume should be tightly pressed onto the drive shaft, are worn. But the car (back in the distant past when it was actually driveable) never gave any symptoms of torque tube bearing problems. Anyway, thanks in advance for checking yours; I'm curious to see what you find.

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[flash]

it's only going to go back as far as the end of the splines. i'll look tomorrow to see what that is.



the torque tube bearings are not as tight as you might think. there is a plastic collar between the shaft and the bearing. to make matters worse, the shaft is coated with a material that tends to wear, leaving a gap between the collar and the shaft. it's a really crappy design, and completely due to the slit in the tube.



i am working with somebody right now to redesign the tube. it should be worked out in the next few days.



we'll see how it goes.

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[Cloud9...68]

"it's only going to go back as far as the end of the splines. "



Which splines are you referring to? The ones in the clutch disk? The reason I ask is that the whole driveshaft assembly is moving, not just the sleeve. In other words, the sleeve isn't moving relative to the drive shaft.



You're right - this seems like a strange design. I would have thought that nothing should move fore-and-aft once the pinch bolt is in place. With the pinch bolt out, the sleeve moves freely relative to the shaft, to allow the sleeve to move out of the clutch assembly to allow removal of the pressure plate - I get that. But given how shallow the pilot bearing is, it seems odd that there's any significant movement allowed of the drive shaft once the pinch bolt is in place.



And I don't want to give the impression that the drive shaft is flopping in the breeze - it does take some effort to scoot it backward. But I would have thought it should take A LOT of effort to get it to move, so I'm a little concerned that something may be worn.

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[flash]

no - i mean that the front part of the shaft is splined over the rear part.



my engine is out right now, and the front part is off of the shaft. i'll play with it in a couple of hours.

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[MB968]

How much motion are you talking about? If it takes a reasonable amount of force, and it doesn't move that far, it could be the way it is designed.



As best as I can tell from the parts manual, the input shaft to the transmission has a bearing at each end that is intended to take any thrust load. It is common in design to have a bit of clearance between the outer race and the housing. This is done a couple of reasons. The main one is to allow the shaft and housing to grow axially relative to one another. If you don't do this correctly the axial growth of one to the other will put such high forces on the bearing if the outer race can't slide in the housing, that it will destroy the bearing. The other way I prefer to design a long shaft that will warm up is to fix one end, and let the other end float in the housing to allow for this relative axial motion.

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[Cloud9...68]

Flash - I'm with you now. Hopefully there isn't enough movement possible to allow the input shaft to come completely out of the pilot bearing.



MB - We're talking about the input shaft to the clutch, not the transmission. I can't get the one to the transmission to move at all. Hopefully the amount of movement I'm seeing on the front end of the drive shaft isn't enough to cause any problems, but I'd like to see some confirmation before I finish torqueing the rear sleeve pinch bolts and the torque tube bolts. So, this is holding me up from re-connecting other things, like the AC compressor and power steering pump, because I don't want to install and tighten their belts if I still have to turn the engine by hand, as I need to do do to torque down the rear drive shaft sleeve pinch bolts.



So, if anyone else besides Flash has their car up on jack stands at the moment, could you please do me a favor and remove the front torque tube window cap, stick a screwdriver between the clamping sleeve and the window opening, and see if you can slide the shaft backwards with moderate effort. Thanks.

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[vliegwielolaf1234]

I have no time right now . but first thing tommorow i wil put my car on the lift and check it for you .

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[tamathumper]

Mine is on the lift with the clutch out. Last week I removed that plug, and could not move the sleeve at all - then I loosened the hex screw, and still could not move the sleeve. Then I removed the hex screw completely and the sleeve slid very easily back, and the hex screw is now back behind the viewing hole somewhere. This was exactly what was described in the write-up I'm using, too, that the hex screw needs to be removed entirely to be able to slide that stub shaft back - http://www.968turbo.com/clutch.htm.

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[Cloud9...68]

Yes, it's true that the pinch bolt needs to be removed completely to allow the sleeve to slide along the shaft. But that's not what I'm seeing. My pinch bolt is now in place and fully torqued (thus not allowing the sleeve to move relative to the front part of the drive shaft that it's around), and, to my surprise, I'm able, with moderate effort, to move the front part of the drive shaft back. I don't know how far, because I don't want to move it beyond the window in the torque tube for fear that I won't be able to move it forward into its proper position.

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[tamathumper]

You can't reach into the bellhousing and grab it if it goes too far back?

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[MB968]

If you can move it enough that you are concerned about getting it out of the window, then it probably has nothing to do with my above comments for the input shaft having some float as it would more in terms of thousands of an inch, not fractions of an inch.

____________

I see I misread your original post. If the rear clamp stays in position, and the front can be moved, I can understand your concern. You said the rear clamp piece doesn't move at all, and the front clutch spline and coupling seems to move axially with the driveshaft. That would leave only two likely possibilities, the driveshaft is a two piece unit (which I've never heard to be true), or the front end of the rear clamp isn't gripping the driveshaft properly.



Anyway to check the front end of the rear clamp. Thats where I'd start.

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[Cloud9...68]

Tama,



Good question - I have the bell housing window in place, so I can't answer your question until I remove it, but if I don't get any replies from anyone as to whether they can move the front parts of their drive shafts the way I'm able to, I think I'll go ahead and remove the window, and if it looks like I can retrieve the shaft through the window, I'll check to see how far back the front of the drive shaft moves. If it's less than my recollection as to the depth of the pilot bearing, I'll forget about this, and continue putting my car back together. I've lost a lot of time already, and there won't be too many days left here in central Texas before it gets unbearably hot in my garage.

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[MB968]

Cloud, I edited my above post. Check out my new comments.

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[flash]

confirmed - the shaft should NOT move



if it does, something is worn or wrong

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[Cloud9...68]

[quote name='flash' timestamp='1334788169' post='125542']

confirmed - the shaft should NOT move



if it does, something is worn or wrong

[/quote]

Holy crap. Now what? The front sleeve is held firmly in place on the drive shaft by the pinch bolt, and, as I showed in the first post, the collar the pinch bolt threads through is in the correct location when the drive shaft is fully forward, so it seems to be correctly located on the drive shaft. And I never touched the innards of the torque tube, so I imagine the situation things are in have been that way for a long time. I think I'll go ahead and remove the bell housing window, and see how far back I can move the drive shaft. But I have to agree that there's no logical reason why the front part of the drive shaft should be able to be moved forward and backward. Any suggestions as to someone I can call who's an expert on the drive shaft/torque tubes of these cars?

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[flash]

move close to the phone

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[Cloud9...68]

Mystery solved! Flash called me to talk through this, and set me straight on the fact that the drive shaft is in fact one single solid unit. So, the only thing that explains the behavior that I'd been seeing is that the drive shaft must be moving inside the sleeve in the back that connects the drive shaft to the transaxle input shaft. He recommended I remove the rear pinch bolts to get a good look at the indents in the drive shaft where the pinch bolts go through, theorizing that they may be worn. But before doing that, I remembered that I had to move the rear sleeve into position to get its pinch bolts to line up, and that I hadn't yet torqued the rear pinch bolts down. Thinking that the pinch bolts fit very snugly against the indents in the drive shaft, I didn't think it was necessary to tighten the bolts very tight (and a guy I trust quite a bit with all things car related told me this as well). But thinking about Flash's theory that the drive shaft must be moving inside the rear sleeve, I decided to go ahead and tighten its pinch bolts - not torqued to 80 Nm, but plenty snug.



Well, it turns out that my belief that the pinch bolts secure the drive shaft fore-and-aft without having to be tightened very much was wrong - once I tightened the pinch bolts, I can now no longer move the drive shaft from the front! And thinking about it, the leverage of the large screwdriver against the window in the torque tube is probably able to exert move force against the front sleeve's clamp (which I had torqued to the full 80 Nm) than I had given it credit for. So, the rear pinch bolts really need to be pretty tight to prevent the drive shaft from moving in the presence of this force.



So, it turns out I never really had a problem. As with all experiences, I learned something. The clamping action of the clamps requires the pinch bolts to be good and snug. Thanks to everyone, especially Flash, who contributed to this bit of troubleshooting.

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