Throw Out Bearing Failure

[john walker's workshop]

the forks can crack . then the bearing is pulled out on an angle.

[jcunning]

Wow!
Now I'm trying to think if I lubed mine before I installed the engine/tranny in my car.

I might have to drop the engine just to make sure.
Of all things I forgot to do...

[RWebb]

pics of all the above

the Bentley has a pic of where the forks tend to crack - run it thru the dishwasher when you remove

I bet you can diagnose and repair whatever is wrong (if anything besides lack of grease) with help here. Be guided by wallet size & DIY interest...

I'd pull the PP and clutch disc for measurement and inspection - easy now that you pulled out the powertrain and cracked it open.

[Walter_Middie]

I removed the engine again - Fourth times a charm.

I use an engine hoist to lift the car - I don't like using a jack when the car gets this high off the ground.

Practice makes perfect - 1 hour and 5 minutes to here:

The fork looks OK from the front.

But from the back - DOH!
I wanted to show the old and the new bearings - because my new Sachs bearing came with a spacer that was too large to use. Maybe others won't be so confused when they see this - here's the new Sachs bearing:
Here's the old bearing:

Notice the size difference in the spacers/washers - new on the left, old on the right:

I did not use the large spacer that came with the new bearing, I reused the spacer on the old. There is nothing to keep the large spacer on there. ????

Well, the mystery is solved.

Mr. John Walker - thanks for the phone consultation, you'll be seeing me and my broken parts at your doorstep soon.

[Mr.Puff]

.

[RWebb]

That part -- all $150 of it -- really needs to be redesigned. The area of cracking should be stronger - the whole durn thing could be lighter, and the wear areas at the horn tips could be replaceable rollers.

[mgbruno]

Hi Walter,
Great Thread. Waiting on my new clutch right now and I definately do not want to go through the same thing that you had to! Subscribed!

Mike

[Walter_Middie]

Well, the engine and trans are back in and working great once again. For the sake of the next guy, here are the symptoms of a broken clutch fork:

• The clutch pedal got noticeably stiffer over just a couple of days.
• Near the end, it got really hard to shift, and putting it in first resulted in grinding.
• Once the clutch fork had really broken, it started to squeal and sounded like a really bad bearing with metal-to-metal contact. This is the sound of your $150 throw-out bearing disintegrating – it takes less than 1 minute to destroy this gem.
• The broken clutch fork is not easy to see until it is really broken – it may start as just a hairline crack. The crack will be on the back side of the fork, which doesn’t make sense to me as this is a pull type clutch. I would think it would break on the front side, where you can see it.

The suggestions I got here on Pelican (right or wrong) kept me going. I was ready to give up, but with a little help, I found the problem. The PNW is really a great place to own one of these cars – I received everything from technical help to offers of help re-installing the engine/trans. Thanks to everyone.

Even though I removed and installed the engine/trans 4 times, I’d still do it myself again. Early on, it was recommended that I get it fixed professionally. This was a good suggestion in that it would have saved me a lot of time, trouble, and work. However, this car is like a family member to me. When it’s feeling good, I feel good – and when it’s feeling bad, I feel bad. When the car is not working right, it’s because of something I did, and I want to make it right again. It’s difficult to explain, but I feel responsible for the health and well being of my car. Last night, I slept really well for the first time in days.

[Superman]

It is very rare that I let someone else work on my car(s). Sure, this means I make mistakes. And learn.

It is also very rare that I remove and replace parts on the 911 without showing the parts to John. There is no substitute for his experience.

[al lkosmal]

Rex,
Good job.....DIY in action. I have a clicking sound coming from my idler gear, supposedly due to incorrect adjustment. (I took it apart, to inspect, last time I had the engine out....and screwed it up) I've dropped the engine tranny 2X to fix and it's still clicking. Now, it's been mentioned that I may have left out a spacer.....aaaaaarrrrrrggggghhhhhh. A pro, like John, would have fixed it 1st time, no problem, but I am going back in. Sometimes I think that I'd be better off to replace my engine/tranny mounts with quarter turn fasteners. Already have fast-on connectors on a lot of the wiring.

regards,

al


headed to the SCCA races at Pacific Raceways, next Saturday (weather permitting). Now that your wheels are together again....head on down for a racing fix.

[dshepp806]

Rex,..kick some butt.

Best,

[mgbruno]

Walter,
Thanks so much for posting your experiences!! It will definately help me in the very near future. I will make sure to do the same!

Semper Fi,
Mike

[Christien]

Jebus bloody chripes and I glad I found this page! I'll be reinstalling the transmission and engine this weekend following a tranny rebuild, and I haven't given the clutch fork a really close examination. I've looked it over cursorily, but I'll now make sure to clean it up really well and have a really close look before I put the transmission back on.

Just so I don't make any more mistakes, can someone answer for me please:
1. is the clutch guide tube part of the throwout bearing? I looked it up in the catalogue and I don't recognize it. If so, I don't need to add any extra grease, right? Because the TO bearing comes pre-greased inside, right?
2. The ends of the clutch fork get well grease - what about the rest of the fork? Obviously it's pivot axis gets greased, but what about the arms?

Sorry if these are dumb questions, but better get virtually slapped upside the head for being an idiot than have to pull the engine and tranny out again!

BTW, just in reference to the discussion about pilot bearing failure on the 1st page of this thread, I can tell you from personal experience that a pilot bearing can fail with absolutely no signs other than gradually worse shifting. I decided to rebuild my 915 because it sprung a leak and was shifting poorly, plus the clutch had started slipping. (by "shifting poorly" I mean it would often grind when shifting, even under normal driving conditions.) Turns out that the real culprit was a completely disintegrated pilot bearing. What this meant (if I'm understanding it correctly) is that my mainshaft would not necessarily stay straight when shifting, and tranny fluid could leak out onto the ground and also onto the clutch, which explains all my symptoms. Sure enough, when I got into the tranny, none of the dogteeth or synchros looked overly bad (for a 36 year old transmission!) but the end of the mainshaft was completely ground down. Details: Christien's 915 rebuild The moral of the story is that a failed pilot bearing doesn't necessarily make any distinct sound, or even have any definite symptoms.

[RWebb]

Guide tube is what guides the TO Bearing - it is the size of a tube of toilet paper - see pics above.

Guide Tube DOES need thin film of grease - grease INSIDE of TO Bearing is so one part of TO Bearing can rotate with respect to rest of TO Bearing (i.e. there are 2 ring shaped pieces that are fit together and pre-lubed). That does NOT affect the ability of the TO Bearing to slide axially along the Guide Tube.


Lightly grease the pilot bearing.

Lightly grease the U-shaped channel on the outside radius of the TO Bearing.

Lightly grease the ends of the 2 arms that form the horn of the clutch fork.

Replace the rubber seal on the clutch fork shaft. Maybe seals, 2 or 3, not just 1 (depends on year).


I know English is not your 1st language, so post pics and ask again if anything is NOT clear.

[RWebb]

more info...

E. Modifications to Improve Maintenance
Take the guide tube and, using a grinder or Dremel, make a small grove in the face that abuts to the transmission case.
This grove should go from the ID bore straight down to the edge of the flange.
The grove should be about the size of half a pencil lead. The purpose of this is to give any leaking transmission oil an alternate path rather than going directly into the center of the clutch.

Then install a second seal in the center of the guide tube as a dam. This forces most leaking oil to go down the new drain grove.
This was just a small commercial seal that did not touch the input shaft.
It was a press fit (about the same fit as the input shaft seal) in the tube with a press tool “of local manufacture.”


from Grady; Transmission input shaft oil seal on a 69 what's involved in replacing?

F. Regular Maintenance

Mark the location of the pressure plate to the flywheel so you can reassemble in the same orientation.
Un-do the pressure plate bolts half turn at a time, going around the circle.
If the disc is oily, replace it. It is not possible to successfully clean an oily disc.

Clean and inspect the pressure plate and flywheel. Replace as necessary.
Get the pressure plate perfectly clean and dry and then thoroughly lube with WD-40.
Wipe off all excess and then get the friction surface only perfectly clean with brake clean.

Now is the time to inspect the pilot bearing.
If OK, add a slight amount of moly grease and rotate the bearing needles with your little finger.
Look behind the flywheel (particularly on the bottom side) for any sign of
engine oil leak from the flywheel seal.
Replacing the clutch and flywheel seal are the main “while you are there” issues.
If you must remove the flywheel, I recommend replacing all six flywheel bolts.

While you have the disc out, clean and inspect the splines. A brass “tooth brush” works well.
Test fit the disc onto the input shaft splines.
Add a tiny amount of moly grease to the splines and slide back and forth on the splines.
Remove every bit of excess grease.

Reassemble the clutch, matching your marks, and making sure all the friction
surfaces are absolutely free of any oil or grease.
Align the clutch disc so it is centered.

Install the throw out bearing on the guide tube with moly grease.
Put some moly on the clutch release arm ball and cup and just a tiny swipe where the fork contacts the bearing.

Reassemble.

[RWebb]

even more...

[none of this got edited for exact models, or overlap - much of it is "Grady Approved"]
Get the pressure plate perfectly clean and dry and then thoroughly
lube with WD-40.
Wipe off all excess and then get the friction surface only perfectly
clean with brake clean.

Now is the time to inspect the pilot bearing.
If OK, add a slight amount of molly grease and rotate the bearing
needles with your little finger.
Look behind the flywheel (particularly on the bottom side) for any
sign of engine oil leak from the flywheel seal.


use brass toothbrush on input shaft splines to clean


Test fit the disc onto the input shaft splines.
Add a tiny amount of molly grease to the splines and slide back and
forth on the splines.
Remove every bit of excess grease.

Reassemble the clutch, matching your marks, and making sure all the
friction surfaces are absolutely free of any oil or grease.
You will need to align the clutch disc so it is centered.

Install the throw out bearing on the guide tube with moly grease.
Put some moly on the clutch release arm ball and cup and just a tiny
swipe where the fork contacts the bearing.

As you mate the engine and tranny, you need to engage the clutch fork
w/ the throw out bearing. One person pushes the trans. and motor
toegther while the other person guides the fork.

Look in the window at the top of the tranny bell housing and see if
the fork is engaged to the TO bearing (flashlight may be needed).
Lean over the motor and hold a mirror and flashlight so you can
actually see the fork engaging the t/o bearing through the hole in the
bellhousing.
clutch inop after engine drop
ll+throw+bearing

Step 2 after bolting the engine to the car should be to reconnect the
clutch mechanism and check the clutch's engagement and travel. If you
screw up, it's really easy to fix at that point.

[gtc]

Originally Posted by Walter_Middie

I wanted to show the old and the new bearings - because my new Sachs bearing came with a spacer that was too large to use.

Ha! That's what you get for stealing the bearing out of my clutch kit!
I'm glad to hear that you have it sorted... I should have my car buttoned up tonight if all goes well.

[Walter_Middie]

Graham,

I've got your throw-out bearing! I wasn't going to say anything just yet - I didn't want to get JW into trouble. Not only are we repairing our trans at the same time, now I have your parts in my car. Pretty soon, my car will consist of parts from all the XXX crowd.

[Christien]

Ok figured it all out. From reading this I was thinking the guide tube was a separate piece. It's not - it's part of the transmission (or at least on mine it has become so after 35 years of weather and heat cycles!). It got greased, as did the clutch fork, and carefully guided into place. I was able to confirm the clutch fork was in place on the TO bearing through the window hole in the starter mounting area. It's really no problem, so long as you have someone hold the tranny while you guide it on and work the clutch fork onto the TO bearing.

[Christien]

Originally Posted by RWebb

I know English is not your 1st language, so post pics and ask again if anything is NOT clear.

What makes you think English isn't my first language? Is my typing/grammar really that bad? FTR, English is my first language (French is my second) Don't worry, I'm not offended or anything, just curious as to what made you think that!