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Are 'Moon Plates' necessary with CV joint replacement?

Am replacing both CV joints, only one of which, has been replaced during my ownership of this 300,000 mile 1980 SC. I have never had any problem with the CV joints loosening, and all of the bolts were tight when i removed them. However, all of the 'moon plates' were absent on both CV joints. At at total cost of $120 () for all 12 moon plates, do i really need them if i have never had any issues with loose bolts? Are the Schnorr washer enough with 'newer' replacemtn CV joints. Found this thread on the subject which made me concerned.

Reconstructing Constant Velocity (CV) Joints
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Old 01-03-2009, 06:32 PM
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i would like to know this as well...my SC had moon plates on one side only.
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Old 01-03-2009, 06:58 PM
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Mine was also devoid of the kidney bean shaped backing plates. Definitely a good idea, but I have had no loosening probems. I check every spring just to be sure (actually I've had to drop my engine/tranny the last two years running)
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Old 01-03-2009, 07:11 PM
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Ok, glad i am not alone. I think i read somewhere that some cars left the factory without them. I have done over 250,000 miles apparently with no problems, so i think i will just check the bolts periodically.
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'79 930/934 replica
80 RSR-look(Now in Sicily)
914/6 2.7 (Projekt 908/3)
1965 Karman Ghia-Class winner 2007 Carrera Panamericana/Ducati 900ss/GhezziBrian STW
D-Zug Produkte/D-Zug.com
Old 01-03-2009, 08:04 PM
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My understanding is the surface/material the bolts torque down on is not solid enough to handle the pressure. And I'd hate to see what happens when one of those half shafts breaks loose. Cheap insurance even at 120 bucks.
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Old 01-03-2009, 08:28 PM
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Just re-doing my CV and axles on my 82 SC.
No moon in sight all bolts where still seated perfectly on the wheel side (and trans; but those came off 1year ago when engine out).
Have seen no wear or markings on the seating of the bolts.
The CV joints carried 82 on them. So I have every reason to believe that they are the original ones from back in the days.
I think if you torque down to appropriate setting you should not have any issues.

Michel
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Old 01-04-2009, 04:06 AM
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juicersr,
When I replaced my axles, there were no half-moon plates installed (the axles appeared to certainly be original equipment). I installed the new axles, several thousands of miles ago, without the plates and all is well... nothing has loosened (have checked twice).
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Old 01-04-2009, 04:39 AM
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Thanks guys. Looks like I am going 'moon-less' as it looks like the factory realized that the plates apparently were superfluous. I tracked my car a lot over last 12 years and no loose cv problems
Old 01-04-2009, 05:52 AM
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Guys,

Tom recognizes the issue.

The necessary Schnorr safety lock washers need an appropriate hardness surface to grip. The tin boot covers and particularly the aluminum ones, won’t hack it. Consequently Porsche installed the ‘moon washers’. The reason that some 911s don’t have them seems to be due to the ‘bean counters’ of the day. They simply left them off to save cost. I think every 911 from ’66 Lobro change from Nadella has used the ‘moon washers’ and Schnorr washers EXCEPT the 911SCs during this era.

What are we to do today?

I recommend you find a set (good used is OK) and install them with the appropriate length bolt and new Schnorr washers. You can turn over the plates (‘moon washers’) and put new Schnorr washers against a ‘fresh’ surface.

The reason the ‘moon washers’ use two bolts is so that it can’t turn under the head of the bolt. A single hardened washer won’t do.

On other threads I pointed out the wide variety of ‘moon washers’. Be sure and use the appropriate style. The issue is side clearance to the tin boot cover.

As I have said on other threads, this is an important safety issue that Porsche AG has ignored. Also important is regular (at least annual) checking of the torque of these fasteners. This is particularly important immediately after removal and reinstallation of the axles. Extremely important with 100 mm CV joints and M8 bolts.

Best,
Grady
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Old 01-04-2009, 06:31 AM
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Hint: Clean the cv bolts with brake clean and let dry. Then put a dab of your girlfriends fingernail polish at the seam between the bolt and the cv. You can easily check for a loose bolt at tech inspection. No crack in the polish, no loose bolt.
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Old 01-04-2009, 06:40 AM
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Quote:
Originally Posted by OldTee View Post
Hint: Clean the cv bolts with brake clean and let dry. Then put a dab of your girlfriends fingernail polish at the seam between the bolt and the cv. You can easily check for a loose bolt at tech inspection. No crack in the polish, no loose bolt.

Just don't let the wife see the strange color of nail polish!
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Old 01-04-2009, 07:28 AM
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Ok I just did a new boots and a re-pack of grease on my cy joints.

I noticed that my joints did not have the moon plates as well. After doing some research I noticed that there are different bolts listed for the 930 joints.


The 85-89 cv bolts are m10x50mm. However, there is also another cv joint bolt lister for years 78-86 that is m10x60mm.

What's the reason for this?

Well, I found that somewhere between probably 85-86, Porsche used a diffrent flange where the boot clamps and bolts to the actual cv joint. Some of the flanges were a type of stamped steel where some of them are about 6mm thick where the bolts and schor washers attach to.

My understanding is that the thinner stamped flange needs the half moon washers where the thicker solid steel one just need new schor washers and maybe bolts.

Furthermore, my thicker style flanges and joints needed the longer 60mm listed bolt in order to thread properly into the cv axle flanges.

I f I were to add the moon plated I would have needed to source an even longer bolt that porsche doesn't have listed for this application.

I decided leave mine the way they were without the half moons as my flange is of the thicker design.

Hope this helps!

-Adam
Old 01-04-2009, 08:32 AM
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get longer bolts of the correct strength
Old 01-04-2009, 09:35 AM
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Quote:
Originally Posted by nocarrier View Post

Well, I found that somewhere between probably 85-86, Porsche used a diffrent flange where the boot clamps and bolts to the actual cv joint. Some of the flanges were a type of stamped steel where some of them are about 6mm thick where the bolts and schor washers attach to.

My understanding is that the thinner stamped flange needs the half moon washers where the thicker solid steel one just need new schor washers and maybe bolts.
Grady, have you found this to be the case? BTW Grady, thanks for your input, as I have a lot of your threads bookmarked in my Pelican 'how too' folder including the the one i posted at the start of this thread.

If it truly was a cost factory over safety, then i will get the moons, as i am going to be driving this car rather spiritedly in Europe for the next 10+ years
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914/6 2.7 (Projekt 908/3)
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D-Zug Produkte/D-Zug.com
Old 01-04-2009, 10:00 AM
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The re-torquing of the bolts brings up lots of issues.

I’m in favor of putting a ‘click-type’ torque wrench on the fasteners at a regular interval. I would choose to set the wrench to the specified torque for the particular fastener. What I’m looking for is; Does the fastener turn before it ‘clicks’? If so it alerts me to a problem. I’m not as interested in the fact that it is now tight as I am in why it was loose.

I’m not comfortable using safety wire and paint. Neither allow you to re-torque the fastener and tell if it moves.

Installing axles and getting the CV joints bolted up is an ungainly process at best. I always want to go back and check my work. The process tends to lend itself to ‘settling in’. This is why it is so important to re-torque after a few miles of operation.

One thing you can do to improve the installation is to modify some old M8 or M10 bolts by removing the heads and cutting a screwdriver slot. These can be removable ‘guide pins’ when installing the CV joints.

If I had a 911 with 100 mm CV joints and M8 bolts, I would convert to the later 108 mm 928S style with M10 bolts – and ‘moon plates’ with new Schnorr washers. .


Pelican Parts has a selection of proper bolts, varying length I think. If not most metric hardware places have the 12.9 grade Allen head cap screws. McMaster Carr for sure. Locally we have AAA Metric in Denver.

The bolt should protrude through the flange 1 threads thread. Make sure there is clearance to the transmission casting when the flange and CV joint is pressed inward to take up the axial free-play.

Best,
Grady
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Old 01-04-2009, 10:30 AM
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ker-bang!

So why is it so important to check these bolts periodically? Here's what happened to my '66 last month. It's a 912 with a 2.2L T4, maybe 130 HP, and an early 901 set up with A-F-M-V-ZD gearset (SWEET match to this motor!). In early December, I started hearing a clunk every once in a while, accelerating as I went around corners. I though, "well rats, a CV joint is going bad" and made a note to take a look. At 480 K miles, one expects stuff like that every once in a while I suppose.

Then as I punched it one morning to pull across a busy street, BANG! and no more drive to the wheels. Honestly, I thought I'd run over something. Coasted it to a parking place, then started it up, and idling in neutral I could see the passenger side halfshaft slowly rotating. Had it towed home.

Apparently, each of the bolts on the right side outer CV had in turn backed out of the flange. Maybe I was an airhead last time I had it apart and forgot to recheck my work? Who knows. 4 of 6 bolts were completely loose, and the last two had given way simultaneously when I hit the gas, and broken off. Thank god no damaged threads in the wheel drive flange, the only bystander damage is that my E-brake cable spacer got whacked and cracked. I replaced it and the damaged bolts, all's back together and running fine again.

BOY WAS I LUCKY!!!! The mind boggles at the possibilities if this had happened on the freeway or a twisty road at speed. Please do check the torque now and again.

Adam912. Out.
'66 912, 480 K happy miles. 2.2L Type 4. S suspension.
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Old 01-04-2009, 11:29 AM
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Looking at my new Lebro CVs vs the old, i notice that the new CV is now a one piece affair, instead of the two piece (flange and CV itself) on the old. Not to beat a dead horse, but does this make any difference regarding the use of moon plates?
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Old 01-04-2009, 01:37 PM
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I can be one more warning to others here...I had a CV let go at 50 mph with no prior warning and it took out the throttle linkage, vacuum line, and my CHT sensor wires (probably lucky in terms of what else could have happened)...pictures of the carnage on this thread:

CV Joint Failure Carnage

I think mine just backed out due to not re-torquing them after they "settled in"...I check them often now but still only use the Schnorr washers on the thick flanges. I was shocked that it could break loose like that without any sound or other indication anything was loose, since I don't think all six bolts could go at once. The fact that it was a Sunday afternoon returning from getting a head start at the office after a 2-week family vacation made it that much worse...this is the only time I've not been able to make repairs or limp home without a tow, including the time my TO bearing separated leaving a parking space...

Olivier
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Old 01-04-2009, 01:54 PM
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still need moon plates

BTW - spelled Lobro
Old 01-04-2009, 02:06 PM
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Look like you have the newer style flange that needs the moon plates on the new cv joint.

The bolts are a different length for the newer cv joints as well.

I believe you need the 50mm bolts instead of the 60mm.

I am not sure if you would have interference issues using the longer bolt. You have to check to be sure anyway.
Old 01-04-2009, 05:33 PM
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