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Discussion Starter · #1 ·
Hi all,

Well I have been enjoying my 70 GT after several years of working on it but yesterday I fired it up after a few weeks of it sitting and there was a loud rattle from the bell housing area. I reversed it down my driveway and pulled it back forward and then parked it. Some details are below:

Car: 70 GT. 1.9 bored to 2.0. Big valve head and combo cam. New fuel system and pertronix ignition.

Symptom:
  1. Rattle when clutch depressed even a little. It sounds like a large rock in a can.
  2. No rattle when under load.
  3. No rattle when in neutral and clutch out / not depressed.
  4. Oil pressure steady at 40psi.
  5. Throw out bearing arm spring still in place and tight. <-- read about that on another article.
  6. I can wiggle the throw out bearing a little up and down as well as forward and back. I am not sure if that is normal.
  7. The transmission (4 spd) apparently had a slow leak and it took ~1 qt of gear oil. I did not notice this since I park it on a gravel driveway and never noticed any discoloration even now... I am not sure if this caused something internally to let go.
I am planning on ordering the 9" clutch set from OGTS with new pilot bearing and throw out bearing to swap it all out.

My Question: Anyone have any ideas on what it could be? I was talking to someone who thought it was a throw out bearing but I thought I would ask here before I go through the trouble of removing the tranny and doing the work. I am on the wait list for a getrag 5spd from OGTS also... so if people think its internal to the tranny I just want to wait.

Someone else I randomly talked to thought it could be a rod bearing.... but I hope that is not the case obviously. Engine sounds great when idling in neutral or when under load.

Thanks as always,

Josh
 

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Opel Rallier since 1977
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Sounds like a throw-out bearing with the grease dried out, maybe a ball bearing gone, or even completely failed and not turning. Could also be a broken clutch finger. Being only when the clutch pedal is depressed pretty much isolates it to the throwout bearing area.

The movement of the throwout arm up and down and around a little is OK.
 

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The release bearing itself usually squeals or chirps, but then again I certainly haven’t heard many other noises it’s probably capable of making, I always quieted by fiddling with the clutch pedal though. There’s two nubs on the clutch fork that tend to wear down. If the clutch arm is in good shape you can rotate them 90° with a good pair of Chanel locks to move the flat spots to the side. I think it’s Clutch arm/TO bearing related. It sounds like you’re on the right track.
 

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Opel Rallier since 1977
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And are you aware that if you use the 9" clutch that you will have to get the flywheel machined down and re-drilled for 6 mounting bolts? The stock 8" clutch will drop right in.
 

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Über Genius
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Throwout bearing. 100%
 

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Discussion Starter · #6 ·
Hi everyone.

Thank you for your help! @ Manta, when Gill called me to pay for the 9" clutch we talked about how the flywheel would have to be machined so I had him change it to the 8" clutch pack instead. It was on sale for over $100 off too which was great. If it was a bolt on upgrade I would have been all for it, but since it would mean more down time for me I just went w/ the 8". I don't want to miss prime driving weather here in Colorado :)

Thanks again for talking to me about this issue. I don't think I could ever restore and maintain my Opel without this forum.

-Josh
 

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Opel Rallier since 1977
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You're certainly welcome! Just one of those 'minor' details to consider. The stock 8" clutch works well.

Now, for sure, understand that once you remove the trannie and clutch, you should inspect the present flywheel friction surface for excessive grooving or scoring, glazing, and/or large burned spots (spots that are discolored like the steel got hot). If not severe, then the surface can be roughed up a bit with a scotchbrite pad or mesh-type drywall sandpaper and cleaned with brake cleaner. But if any of these issues is severe, then the flywheel ought to be removed and the surface freshly machined. Otherwise, you may end up with clutch chatter (quick staccato grabbing of the clutch when you release it) and other clutch problems. So you amy not be out of the woods on that matter. Bt you won't know 'til you get it apart.

Has the clutch operation been smooth up to this time? And if you want to take pix of the flywheel and post, feel free to ask for opinions.
 

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Über Genius
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Check your pilot bushing/bearing too. If it's bad you can ruin your clutch within miles.
 

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Another thing to consider since you will be in there anyway. I have had more than one flywheel come loose in past years, that’s right, all six bolts loosen. It’s nice that the noise forewarns you.
 

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Another thing to consider since you will be in there anyway. I have had more than one flywheel come loose in past years, that’s right, all six bolts loosen. It’s nice that the noise forewarns you.
Blue Loctite should be put on all clutch and flywheel bolts.
 

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Opel Rallier since 1977
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Well, that is indeed a mystery.....I've lost count of the clutch/flywheel and torque converter/flexplate installs done here... and never had anything come loose, even in rallying and revving repeatedly to 8000 rpm, all sorts of clutch slamming, etc. (Applies across many brands of cars and engine models too.) If the bolts came loose and then were reused, then the threads may be worn/distorted and the mating threads in the crank may be also.

Are you using a torque wrench and tightening in 2 or 3 steps?
 

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Yes, and as you can see, I’ve also sheered all six bolts including the anti-sheer bolt. We are in agreement, I don’t have an explanation.


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Opel Rallier since 1977
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Are these the factory/OEM bolts being used? They have to be hardened bolts like the factroy ones.... metric grade 10 or 12.

Anything special about the engine? Stock 1.9L or ????? Being raced or autocrossed? Are you dumping the clutch at launch with high revs? (All my racing was in rallies... it's hard to shock the drivetrain much on gravel.)

Looks like excessive grease in the pilot hole and oil getting out of the seal. Not sure if that could contribute....

I also have to wonder if the raised flange on the end of the crank, that precisely centers the flywheel, or the mating center hole the flywheel, is worn or damaged. If so, and the flywheel centers loosely on the crank, then things will be shift and be imbalanced and put a shearing stress on the bolts. That flywheel-to-crank fit ought to be super snug.
 

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They were stock bolts, correctly torqued snug fitting. The sheer was the result of a missed shift in the canyons and a sloppy, worn trans. Even so, I’ve only seen that in the days of drag racing with much higher power, not 80 bhp 1.9s. Those bolts were probably 45 y o and who knows how many times had been torqued.


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