Flange Wear from CV Joint Options

[frank_c]

Today I started the process of dropping the engine & transmission so that I can send the transmission off to Dr. Evil and take care of some misc engine work (rear main seal, oil return tubes, etc. ). As part of this work I was also hunting for a clunking noise I hear from the back when the car is stopped and as I let the clutch out and the car just starts rolling forward. I already checked and/or replaced all suspension and engine mounts, as well as the outer CV joint bolts (inners are safety wired) and found nothing loose. So next on my list was either the CV joints themselves, or possibly loose flywheel bolts.

When I removed the inner CV joints from the transaxle flanges, I was surprised to see some pretty deep gouges in the flanges from the CV joint inner race/star (see photos below). This seems like a good candidate for the noise I am hearing.

I have never seen this type of wear before with any of the other cars I've worked on - what would cause this? I noticed that there is not much grease in the joints, which I suppose is one possibility. Was the inner race put on backwards? Wrong parts? I did confirm that the axle shaft does move in and out freely at the outer CV joint.

Thanks for any insight.

Left flange:


Right flange:


Circled area shows where inner race is cutting into the flange.

[Jack Standz]

"I have never seen this type of wear before with any of the other cars I've worked on - what would cause this"

Typical wear from 50+ years. Replace (CVs, axles, etc.) worn parts. Lately, we've been replacing with PMS flange adapters and Carrera axles (930 CVs) due to the fact that original style 914/4 CVs aren't available.

[Superhawk996]

That isn’t normal wear. The CV spider should never be plunging far enough to come into contact with the flange.

You have some sort of mismatch somewhere.

Possibilities:
CV joint was previously disassembled and not reassembled properly as you speculate.

Flanges not correct / not seating deep enough into differential?

Axle shafts too long?

Wrong CV’s - maybe someone using the wider 944 CV’s without proper machining mods to 914 axles? (Not sure this is possible without doing the axle machining to get the CV onto the axle)
http://www.914world.com/bbs2/lofiversion/i...php?t80641.html

Don’t know if you’re running non-stock trans position / angles / ride height that is resulting in too much axle plunge?

[bdstone914]

That isn’t normal wear. The CV spider should never be plunging far enough to come into contact with the flange.

You have some sort of mismatch somewhere.

Possibilities:
CV joint was previously disassembled and not reassembled properly as you speculate.

Flanges not correct / not seating deep enough into differential?

Axle shafts too long?

Wrong CV’s - maybe someone using the wider 944 CV’s without proper machining mods to 914 axles? (Not sure this is possible without doing the axle machining to get the CV onto the axle)
http://www.914world.com/bbs2/lofiversion/i...php?t80641.html

Don’t know if you’re running non-stock trans position / angles / ride height that is resulting in too much axle plunge?

@frank_c


I agree with the above reply. Never seen that wear.
Is it both sides? Have you pulled the axles and checked to see if it happened on the outboard CBs?
Need to look at nothing sides of the center of a cv to see if that could happen from wrong installation.

[914Sixer]

It is a rare but I have seen in before in stock axles.

[Jack Standz]

It is a rare but I have seen in before in stock axles.

Me too.

Not what you could call "normal" wear, but have seen similar wear like that on an old/used 914 transmission flange. If the flange is going to be reused, it shouldn't have any negative impact because your CV, when in normal condition shouldn't contact the flange there. Interested to see the wear on the CV or condition that caused this.

The problem now is how to get replacement CVs if that's the plan. Go with 911 axles (930 CVs) with adapters from PMS? Or PMB has these:

https://pmbperformance.com/products/porsche...84588&_ss=r

[930cabman]

It is a rare but I have seen in before in stock axles.

(IMG:style_emoticons/default/agree.gif)

I also have seen this "condition", do not know the cause, but any metal particles in this area cannot be a good thing

(IMG:style_emoticons/default/popcorn[1].gif)

[frank_c]

Thanks for all the responses. Please find my answers below to some of the comments/questions:

1. CV joint was previously disassembled and not reassembled properly as you speculate.

A: I was looking into to this some more this morning, and from the images of the inner race/spider I have a hunch on what might be going on. See below.

2. Flanges not correct / not seating deep enough into differential?

A: Other than the older 911 flanges (which should be ok), what else would fit?

3. Axle shafts too long?

A: Based on what I found this morning, this is seeming like a more realistic possibility. See below.

4. Wrong CV’s - maybe someone using the wider 944 CV’s without proper machining mods to 914 axles? (Not sure this is possible without doing the axle machining to get the CV onto the axle)

A: The CVs don't appear to be the wider 944 part - and as you mentioned, if they were the circlip would not fit without machined axles (I checked and the axles don't appear to be machined).

5. Don’t know if you’re running non-stock trans position / angles / ride height that is resulting in too much axle plunge?

A: I did have the car corner balanced and they set the ride perhaps a little lower, but nothing extreme.

6. Is it both sides? Have you pulled the axles and checked to see if it happened on the outboard CBs?

A: Yes, both sides (pictures in original post show L & R). I haven't pulled the axles yet, but based on how little grease there is on the inboard CVs, I will likely be doing that at least to get more grease in there.

Update:
I did some further inspecting of the CV joint this morning, and found something else alarming that I've never seen before that points me to believe that one or more of the parts are not correct here. Note that I purchased the car back in February, and I'm still in the 'discovery phase' in finding and fixing things.

As a side note, the rear wheels were very difficult to turn by hand with gearbox in N. Now with the inboard CVs disconnected they turn very easily. I suspect the CV spider interfering with the flange when the wheels were at full drop contributed to this.

Observation 1:
The inner conical washer has grooves worn in it from the CV balls (see photo). Maybe this is considered normal wear, but I have never seen this before on any of the Porsches and BMWs I've worked on. This seems to fall into the "axles shafts too long" bucket.




Observation 2:
From looking at 914 CV joint images this morning, I noticed that there is a difference in the spider shoulder height for the Porsche part vs. the GKN/Loebro part, the latter being much taller and appears to match what is installed in my car.

Notice the height of the yellow arrow in the two images below that I pulled from online vendor sites. The height of the spider on the Porsche part is much shorter and has a bevel cut in the edge (red circle).

Porsche part:


GKN/Loebro part:


And here again is the CV from my car with the taller shoulder height shown (& no bevel):


So is it the GKN/Loebro part alone that is causing the issue? If so, I would think others would have discovered this by now.

I would like to push the 'easy button' and simply order the completely assembled 914 axles and CVs from PMB, that way I know I would have the correct axles, but I see they use the GKN/Loebro CVs - so there is a concern there.

If my axles are correct (does anyone have the length of the 914 axle shafts handy?), then I would feel safer purchasing the Porsche CVs.

Thanks.

[frank_c]

The problem now is how to get replacement CVs if that's the plan. Go with 911 axles (930 CVs) with adapters from PMS? Or PMB has these:

I've seen other posts mentioning that the OEM CVs are NLA, but I see that both Pelican and SMC have them listed as available. What am I missing here?

https://www.pelicanparts.com/More_Info/91433202903.htm

https://sierramadrecollection.com/products/...-914-332-029-03

[Superhawk996]

“ Observation 1:
The inner conical washer has grooves worn in it from the CV balls (see photo). Maybe this is considered normal wear, but I have never seen this before on any of the Porsches and BMWs I've worked on. This seems to fall into the "axles shafts too long" bucket.”

The joint is clearly hyper-extending.

I’m not trying to be a dick to any of the others that have posted, they are all good guys and have been playing with 914s for years . . . but go with your gut. Regardless of what anyone is saying they have seen, or have rarely it may be, it isn’t normal and it isn’t that way by design. I say that as an automotive engineer with 27 years experience in the industry. No one would design or build a CV that is going to create metal debris inside the CV from interference between the CV and the flange. It’s really that simple.

Having seen these marks before is like me saying I’ve seen spun main or rod bearings in a stock engine. Just because it has been observed before, and it’s rare, doesn’t make it normal or correct.

You’re going to have to disassemble and potentially measure to figure out root cause. Definitely have to replace as those joints are trashed by the debris on top of whatever caused the contact in the first place.


To reiterate:
Something is drastically wrong - apologize I can’t pinpoint what it is.
GKN / Lobro are quality joints but need to be correct joint for application.
PMB is a reputable supplier. Contact them for parts when you get to that point.

[Superhawk996]

The problem now is how to get replacement CVs if that's the plan. Go with 911 axles (930 CVs) with adapters from PMS? Or PMB has these:

I've seen other posts mentioning that the OEM CVs are NLA, but I see that both Pelican and SMC have them listed as available. What am I missing here?

https://www.pelicanparts.com/More_Info/91433202903.htm

https://sierramadrecollection.com/products/...-914-332-029-03

(IMG:style_emoticons/default/headbang.gif)

Oh boy - here we go again.

Those joints are for the 914/6 splines and will not fit 914/4 axles (different spline counts)

Porsche has (IMG:style_emoticons/default/sheeplove.gif) the pooch on their part numbering, and none of the suppliers care enough to address the issue and keep selling the wrong parts. Search the forum and you’ll see this issue is well documented since about 2019.

I have a set of 914/6 axles and have purchased those joints and have confirmed what they fit.

Now, maybe the situation has changed . . . But doubt it. Call PMB (not affiliated)

[Jack Standz]

"I have never seen this type of wear before with any of the other cars I've worked on - what would cause this"

Typical wear from 50+ years. Replace (CVs, axles, etc.) worn parts. Lately, we've been replacing with PMS flange adapters and Carrera axles (930 CVs) due to the fact that original style 914/4 CVs aren't available.

OK, I want to revise my wording a little. As mentioned, I've seen this type of wear/damage to transmission flanges before (although, after looking at the photos again this is the worst case I've seen). I've also seen 50+ year-old CVs with deep pockets worn in the groves where the ball bearings move back and forth. Seen broken cages, etc.

So let's say it's not "typical" and definitely not normal. Let's call it "odd". Particularly if these CVs have been maintained or replaced fairly recently. That's different. That indicates improper procedures were performed or improper parts installed. Maybe that's the case here. Additional information would help. Maybe these aren't 50 year old CVs.

Still looking forward to finding out the cause. My money is on hyperextended CVs like @Superhawk996 said. But, why? Could the CVs wear so much that they can hyperextend? Could these CVs not have enough travel to articulate sufficiently for this 914's needs?

[930cabman]

In the few years of my 914 "habit" I have mixed and matched axels, CV's (inner and outer) but must have gotten lucky.

I can check the length tomorrow, I have a pile of bare axels

after 50+ years of mechanics, might even be a DAPO in that lineage, just about anything is possible

[Jack Standz]

914/4 axle length:

http://www.914world.com/bbs2/index.php?showtopic=171960

[frank_c]

First, I want to say thank you to everyone who has chimed in here to help identify what might be going on - I really appreciate it. I've owned and worked on 911s for decades, but I'm only about a year into climbing the 914 learning curve, so still much to discover. Btw, my Patron badge is not up yet, but I did make a contribution about a week ago.

Those joints are for the 914/6 splines and will not fit 914/4 axles (different spline counts)

Ah, OK. It's surprising that this has been an issue for so long and it has not been corrected yet. Thanks for saving me from ordering the wrong parts. This makes the decision to go with the assembled units from PMB an easy one - easy button it is (IMG:style_emoticons/default/smile.gif). If it turns out that my axle shafts are indeed too long, then I suspect I won't be able to use them as my core return to PMB - but I'll call them if that situation arises.

[Superhawk996]

Those joints are for the 914/6 splines and will not fit 914/4 axles (different spline counts)

Ah, OK. It's surprising that this has been an issue for so long and it has not been corrected yet. Thanks for saving me from ordering the wrong parts. This makes the decision to go with the assembled units from PMB an easy one - easy button it is (IMG:style_emoticons/default/smile.gif). If it turns out that my axle shafts are indeed too long, then I suspect I won't be able to use them as my core return to PMB - but I'll call them if that situation arises.

If you care some of the history is here and I’ll put the link here for anyone else that stumbles into this in the future (post 20)

http://www.914world.com/bbs2/index.php?showtopic=350293

[frank_c]

914/4 axle length:
http://www.914world.com/bbs2/index.php?showtopic=171960

Thanks for the link. I'm going to try to get at least one of the axles out after dinner and measure it to see how it compares. I'll report back here with what I find.

[Krieger]

When I disassembled my 75 thirty years ago both my flanges had that wear pattern. I replaced the flanges and all the cvs. At the time I chalked it up to the broken engine mounts and or the bent to crap engine mount bar. Since that time I have found that same wear pattern on two of the three spare transmissions I have acquired. The flanges on my 72 were fine. So that make 3 out of 5 transmissions for me... (IMG:style_emoticons/default/confused24.gif)

[Krieger]

I kept these to use as tools. (IMG:style_emoticons/default/biggrin.gif)

[frank_c]

I kept these to use as tools. (IMG:style_emoticons/default/biggrin.gif)

Wow - thanks for posting that photo. The one on the left looks very similar to the damage on my left flange. So, I'm not alone..

I wasn't able to get the axles out tonight to measure them - it looks like I would need to remove the heat exchangers in order to do so, and I'd like to avoid that. So, I'll wait until after the engine is out to remove the axles - targeting mid-week.

Out of curiosity (and to confirm to myself that I didn't overlook this type of wear before) - since my '73 911 is conveniently disassembled, I took a look at the flanges on its 915. As you can see, not a scratch: