strange flywheel wear pattern, '91 348

Any pics???

 

Tom, I think the only way you could get damage like that would be if you installed the rear cover (with the Cavallino) while the central hex screw was backed out from the ring nut. There is supposed to be a fairly substantial air gap between the cover plate and the ring nut / hex screw. If the hex screw just worked loose, I can see it rubbing on the rear cover, but I don't think it would cause that big crack in the cover. Strange damage.

I'd be most interested to see the unusual wear pattern on your flywheel.

 

This may be hard to understand, but I think this is what happened. Look at the color diagram. I think someone failed to screw the hex screw (yellow) into the ring nut (orange) before they installed the rear cover (brown). This has two effects. First, because the hex screw is actually hitting on the cover, it prevents the cover from seating all the way down against the bellhousing. That would be OK if the cover was JUST a cover. But the cover has a second function. It also seats the flywheel support bearing (blue) into the bellhousing (pink). Look at the joint between the bellhousing and the cover plate. If those two are not fully in contact with each other, then each time you push in on the clutch, that bearing moves backwards until it hits the cover plate. In other words, the entire rotating clutch assembly is moving back and forth. The bellhousing remains stationary, because it's bolted to the transmission case, but inside the bellhousing, the clutch itself is moving, which destroys the set-up height and sends everything out of whack (hence the abnormal wear pattern on the flywheel).

Who did your last clutch job?
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Jeff,

JEEPERS! Did you draw that up?

Excellent post... and the mark of a real, true professional... care to make a trip to Kuwait for a week or so???



Mike in Kuwait

 

If you look at the relationship between the flywheel, the bellhousing, the bearing, the ring nut, and the cover plate, there is no way that the clutch assembly can move back and forth unless that bearing isn't properly located. And if the cover plate was indeed installed correctly, then the only way the clutch can move back and forth is if the bearing is the wrong width. Otherwise the bearing is absolutely clamped into place. For now, I stand by my guess/hypothesis. The nuts securing the rear cover may have been tight, but was the rear cover actually tight up against the surface of the bellhousing??? Or was it jammed against the hex screw?

No, I didn't make that drawing, I just colored it for clarity.

 

After seeing this pic, I reckon that the centre hex nut was left wound right out. They forget to screw it in, then put the cover on using the 4 nuts to pull the cover in, cracking it.

I could be wrong here, but I dont reckon that the hex bolt being left loose, would un-wind into that cover and cause it crack like that. Of course it would have the mark in there where it has been rubbing, as you can clearly see, but I dont think it would have cracked the cover.

If the hex bolt did come loose and wound out there being stuck and not able to fall out of the hole because there is not enough clearance, then I would think it would just sit there and eventually wear a hole in the cover. It is only cast that little cover. It would not have taken long. The same time, the hex bolt head would have been wearing down. But not by much, as its a steel bolt, not sure of the grade though?

 

PAP 348 and Miltonian are right. The screw might vibrate out until it contacts the cover (I really doubt it though) but there would be no way it could exert any real force against it. The last person in there did that.

 

Yes, you WOULD think that.

Ive seen some rough sh*t in my time, so I wouldnt be suprised mate.

 

Like a three legged coal mine donkey????????

 

Cool! Plus the bonus is that machining the flywheel took a little bit of weight off of it. You should love the way she runs now!

 

Good to hear you will have it back on the road soon Tom.