CV Joints Again

[GSECLINT]

Before cleaning and repacking all my cv joints, I read all the posts regarding using the proper fasteners, washers & moon plates. Then on disassembly, I noticed one of my flanges has a bolting surface with a raised portion and a recess for the bolt/washer. It appears this surface is incompatible with using a backing plate. Also, when I disassembled my joints, none of the flanges had a backing plate. I have had the car for three years, 10,000 miles without a bolt loosening.

What is the final word on these moon (backing) plates, needed or not needed? and do I have some kind of one off flange?

Thanks

[RWebb]

what car??

[GSECLINT]

912E, should be same running gear as 911.

Thanks

[greenspeed]

Now don't shoot me - and I immediately bow down to the vastly experienced posters on here.

sorry to come back to this again but what was the outcome?

If you look at gse clints flanges' (above) you will notice a step in the flange surface which will not allow the moon plates to sit flat ( thats if you can find 8mm moon plates).
If you install the moon plates to this setup will they not be bearing ( pushing)on only half the flange surface?
Also as the cap head screw ( called a shouldered allen bolt over here ) gets longer do the clamping areas ( ie the head and the point of thread contact) not get further apart and therefore more susceptable to shuffle ( back and forward movement which might cause the bolt to back off)
I am not trying to stir the manure- i am confused as to the best plan of action.
(as I will only be using the car for track events I will be checking torque before every event)

Obviously when I go for my rebuild i will be going for the bigger 108mm driveshafts with 10mm bolts torqued to 60 ish pounds .

in fact when I took the dive shaft off last night I was amazed at how puny the original set up was ( 8mm 50mm bolts and no moon washers) on my car.

sorry for the long post.
peter

[GSECLINT]

Peter,

I installed the the driveshafts without the backing plate. My car is a 912E, around 80 HP so the shafts are not going to see the kind of torque that a 911 would. Also, they were $10 a piece. Periodically I take a peek to see if anything has loosened up. So far, so good.

Considering how you are going to be using your car, and if it were me, I would use the backing plates along with the safety wires. A failure of the shaft(s) in a racing invironment would be catastrophic!

Good Luck
Clint

[Grady Clay]

Peter, greenspeed,
First, WELCOME to the Forum
You will find a lot of help here.

Chris, GSECLINT thanks for the revival of the thread.
It is too bad it died from our neglect in March.
It will be useful to see the solutions.


One of the great difficulties with this subject is the ‘way-too-many’ different CV joints, flanges and boot tin that Porsche has used, insufficient documentation, and the wide range of replacement parts (Original Porsche, OEM, aftermarket and whoknows whatever else).
As the automobile industry changed to “Lobro-type” CV joints, every aftermarket supplier found “something that fit” every application, regardless if it was the proper application.
I’m sure there are 911s (and 912Es) driving around with CV joints intended for a 1600 cc lightweight Asian sedan.
One of the really good triumphs of Pelican Parts is their efforts to sort through all the ‘junk’ and find good (and ‘priced right’) aftermarket alternative as well as supplying Original Porsche and OEM parts.

Part of the real benefit of the Forum is the wide sample of cars addressing this issue.
We are also uniquely situated to sort through this and find the best set of parts for each application.
… and we have the inclination to make our cars ‘right’.

For example, Clint’s type 923 (100 mm diameter, M8 bolts) CV joints are probably perfectly suitable with the 2.0 engine.
If that car were to get a powerful 3.6 transplant, the 928S (108 mm, six M10 bolts, end cap) CV joint axle assemblies used on 911s from about 1986 are appropriate.


Looking at this original image, there are a couple of important questions and features.





First, clearly the boot flange on the right cannot use ‘moon plates’.
It appears neither CV has ever used the plates.

The purpose of the ‘moon plates’ is to provide a surface of intermediate hardness between the very hard teeth of the Schnorr washers and the (usually softer metal) of the earlier tin boot flanges.
Both of these boot flanges show deformation from the Schnorr washer teeth.
It would be useful to compare this deformation to the marks under the heads of the socket head cap screws.
With ‘moon plates’, the deformation imprints in the plate and bolt were roughly the same (indicating roughly equal hardness).

Are either of these boot flanges aluminum?
I have seen boot flanges that were aluminum – probably non-Porsche.
Aluminum flanges (boot ‘tin’) must have ‘moon plates’ for the bolts to not deform the aluminum under the bolt-head and allow the joint to slip.

With these above boot flanges, they appear softer than ‘moon plates’. The right flange (teal arrow) appears to have more deformation than the left flange (green arrow).
Is this a problem?
Probably not with a 912E.
The BIG ISSUE seems to be with the 911s (2.7 and particularly 3.0 & 3.2) that were originally equipped with the 100 mm type 923 (912E) CV joints.
I would like to know if there was any (unannounced) Factory communication about maintaining the integrity of the connections between the CV joints and the transmission and stub-axle flanges.
When an axle comes loose, really bad things can happen.


Another issue is with the length of the CV joint bolts.
Assuming one of these boot flanges is original and the other is a replacement part, it appears they are the same thickness (red arrows).
In this case there should not be a bolt length issue.
There becomes a safety issue when the original boot tin is then sheet metal (~0.5 mm) and the replacement CV joint boot flange is thicker (~6.0 mm) – as above (red arrows).
In this situation, appropriately longer CV joint bolts are required.

The CV joint bolt should protrude though the axle flange 1-2 threads (1.5 is ideal).
Too long, the bolt can contact the transmission casting.
There should NEVER be multiple washers under the bolt-head only one (new) Schnorr Safety Washer.
The bolts should always be ISO strength class 12.9 (previously DIN 12g) socket head cap screws and replaced with new if worn or damaged.

Peter, the length of the CV joint bolts is not an issue here.
It is the total clamping force provided by the six bolts (six times 8x1.5 thread pitch times 33 ft-lbs torque) that secures the metal-to-metal contact between the CV joint and the transmission axle flange (or stub axle flange) that transmits the driving torque without slipping (‘shuffling’).
The bolts themselves do not provide any transmission of the driving torque (unless there is slip/shuffling and then it is too late).

Here is the best thread on this subject:
Reconstructing Constant Velocity (CV) Joints
While long, it is worth studying end-to-end.

Here is a more extensive list:
Pelican Parts Technical BBS - Search Results

Best,
Grady

[1-ev.com]

Grady, Thank you always !!! for all your responses.

I've installed moon washers on mine 912 (VW) axles I've bought from our host.

I've to reinstall used moon washers, just flipped them with better (unused) side up.

I could not find the new ones ... NLA...

I've been reading your inputs in CV joint rebuild thread (Before starting the work) - Great Info!!!

Thank You again.
-Youri

[Nine9six]

I was going to chime in here...Till I saw Grady had replied...He pretty much says it all with competence and completeness.
The back spot facing of the flange on the right, is due to the step on the back face of the flange. Whatever the reason, it looks hillbilly to me, and I'd look to replace the falangee, (humor) with one from a dismantler that matches the left.

[greenspeed]

Grady,
Thank you for your gratious welcome, and for taking the time to explain to a newbie.
Your posts are brilliant and informative and may I say very generous in spirit!
Thank you

[Grady Clay]

Thanks guys, but I learn from you something new every post.
Keep it coming.
Lame ol’ me (and all of us) need more data.

Dealing with this seemingly ‘simple’ subject of Porsche CV joints has become subject for someone’s PhD dissertation - and it is not going to be me at my age.
The ‘bits-&-pieces’ posted here should (will?) become the basis for the definitive work on this subject.
That can be described as: “Porsche CV Joints, Axles and Flanges”.
I hope the Pelican “Wiki-like Project” can be the repository of the knowledge.

Please keep the details (and measurements!) coming.

Best,
Grady

[stormcrow]

Grady

The most important thing you need to be concerned about is making sure you have thread showing on the other end of the flange bolt as was mentioned. I changed mine on my 78 SC Targa and the new flange was thicker. Everything fit fine but I didn't check the flange bolts to see if I had thread showing.

Well two days later I put a load on the engine coming up the on ramp to the interstate and around 85 MPH the axle let loose and kaboom.

The CV joint came loose at the transmission - and damaged the shift linkage and the heater box that surrounds the exhaust manifold - I was lucky nothing else was damaged. Still, had to remove the engine to fix the tranny.

This is very important to check.

SteveKJR

"A Porsche does more then just go fast in a straight line"

[1-ev.com]

Originally Posted by stormcrow

Grady

The most important thing you need to be concerned about is making sure you have thread showing on the other end of the flange bolt as was mentioned. I changed mine on my 78 SC Targa and the new flange was thicker. Everything fit fine but I didn't check the flange bolts to see if I had thread showing.

Well two days later I put a load on the engine coming up the on ramp to the interstate and around 85 MPH the axle let loose and kaboom.

The CV joint came loose at the transmission - and damaged the shift linkage and the heater box that surrounds the exhaust manifold - I was lucky nothing else was damaged. Still, had to remove the engine to fix the tranny.

This is very important to check.

SteveKJR

"A Porsche does more then just go fast in a straight line"

Steve,

Are you saying to check all bolts protrusion and torques and no grease on threads? ... lol.. just kidding...

I think bolts wiring idea on top of the "moon" and new Schnorr Safety Washer should be not considered as overkill, but rather STANDARD ...

Here is thread about it Safety wiring CV joints

I hope that some manufactures can offer bolts with holes, that we do not have to drill them 1 by 1 ...

Here is HF sells safety-wire pliers http://www.harborfreight.com/9-inch-safety-wire-twister-45341.html

My 2c..

Thank you.
-Y.

[Grady Clay]

Guys,

From my 2003 post: Safety wiring CV joints I consider safety wire a ‘last line of defense’.

Back then I reported:
“The lines of defense to prevent these bolts from loosing are; perfect threads, new Skorr [sic] washers, proper torque, re-torque, and (last line) safety wire.”

I would modify this as:
New bolts,
Perfect clean dry (grease-free) threads,
New Schnorr washers,
Proper torque,
Advance installation procedure (see below*),
Re-torque after ~100 miles,
Periodic re-torque (about every 3K miles, much more often for track use).
and
Last line safety wire.



It is critical to understand that you cannot simply skip to the ‘last line’ and have a secure joint.


A major difficulty with safety wired bolts is you must remove the safety wire in order to re-torque.
Too often this precludes the re-torque and simply (inappropriately) rely on the safety wire.
To understand why is to understand how the driving torque is sent through the system.

It is the clamping force that applies pressure to the steel-to-steel contact surface between the CV joint and the flange that transmits the driving torque.
The bolts only apply the clamping force, they do (never should) not transmit driving torque.
If a bolt were to loosen (where safety wire prevents more release) the clamping force has already released where joint slip is already occurring.


Yes, safety wire probably gives a slightly longer time between initial joint slip and bolt failure.
This time may allow the driver to hear noise before the impending disconnect failure.


You would normally expect racers to embrace safety wiring the CV joint bolts.
That is not the usual case because having the (easy) availability to re-torque the bolts takes priority.
Additionally, being able to disconnect and re-connect an axle in a race situation precludes safety wire.



*Here is an improved method of attaching your CV joint to the flange:
1968 2.0L Engine Tuning
There are two significant benefits to this technique:
First, it reduces the chance of getting grease between the joint and on the bolt threads.
Second, the new bolts and Schnorr safety washers are ‘virgin’ to their clamping and retaining application, allowing better retention.

It is important to understand the function of the intermediate hardness of the 2-hole ‘moon plate’ washers.


Yes, later (after several re-torques) safety wire is desirable.
No, it is not a substitute for underlying fastener technology.


This discussion is critical for the 911 years with the 100 mm, six M8 bolt type 923 CV joints.
These 100 mm joints were for the 2.0-liter 912E and (IMHO) overstressed with a 911 2.7, 3.0 & 3.2 application.
In my opinion the correct ‘fix’ is to install the 928S 108 mm, six M10 bolt CV joints used form about ’86 in the 911 Carrera.

Porsche A.G. should have a very low cost upgrade available for this deficiency.

Best,
Grady

[1-ev.com]

As always, Grady You are the Best !!!

Thank you.
-Y.