CV Joint and Axle/Half Shaft Compatibility

[Tom '74 911]

Hello -

The current axle/CV setup in my '74 911 is stock; ie: stock '74 915 output flanges and stub axles w/the larger flanges and (4) 10mm bolts & 2-pin CV bolt pattern. The 915 I am replacing the stock one with (due to an engine upgrade) has 108mm (or is it 110mm?) output flanges w/(6) 10mm bolts. I know I can drill out the pins in my existing CV joints and replace them with bolts but as an alternative, could I replace the inner CVs only with this one: Porsche 911 & Carrera Axles & Bearings - Page 1

Is this the correct one and are the half shaft splines the same as my '74 half shafts? Basically, I'm trying to avoid buying entirely new complete axle assemblies and would like to know if CVs across different years can be fitted to different half shafts, and if this is the correct one for my application.

I tend to over think things so let me know if there is a simpler way.

Thanks a lot,
Tom

[Tom '74 911]

Sat. AM bump.

[Flat6pac]

I would either wire the 10mm bolts together and use the 4 bolts or drill out the CV to install the extra 2 10mm bolts.
The better option would be find 2 good used sealed half shafts that go all the way to the stub axel from the 85 to 89 and install them complete. Remember you need the nut and washer for the outboard to match the half shaft stub axel
Bruce

[Grady Clay]

Drill the CV joint and tin boot retainer for the other two bolts.
This is easy, ends up the same as the ‘928’ CV joint and doesn’t cost anything.

Having six M10 bolts is very desirable.

If someone has the answer to the spline size inside the early 108 mm CV joint and the ‘late’ (928) 108 mm CV joint, please post the details.

This is a very worthwhile thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/222537-reconstructing-constant-velocity-cv-joints.html
Long but worth studying.

Rember to use new Schnorr washers, torque to 63 ft-lb and again after about 100 miles.

Best,
Grady

[Tom '74 911]

Originally Posted by Flat6pac

I would either wire the 10mm bolts together and use the 4 bolts or drill out the CV to install the extra 2 10mm bolts.
The better option would be find 2 good used sealed half shafts that go all the way to the stub axel from the 85 to 89 and install them complete. Remember you need the nut and washer for the outboard to match the half shaft stub axel
Bruce

Bruce,
Thanks for the reply. Your solution, to source entire half shafts w/later CVs, is one I considered but am trying to avoid as I need to draw the line somewhere. Project creep is a disease that I am fully infected with. I am planning to drill my inner CV to use (6) M10 bolts, as Grady suggests, but am thinking that for safety and reliability w/my soon to be upgraded motor, my CVs should probably be replaced w/in the next year or two due to wear. I rebuilt them last year and decided they could last another year or two (based on my nonexistent experience). I was thinking that $76 ea. for 2 new (later) inner CVs would be something I could swing, but I am not certain if they would fit my '74 axles.

Originally Posted by Grady Clay

Drill the CV joint and tin boot retainer for the other two bolts.
This is easy, ends up the same as the ‘928’ CV joint and doesn’t cost anything.

Having six M10 bolts is very desirable.

If someone has the answer to the spline size inside the early 108 mm CV joint and the ‘late’ (928) 108 mm CV joint, please post the details.

This is a very worthwhile thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/222537-reconstructing-constant-velocity-cv-joints.html
Long but worth studying.

Rember to use new Schnorr washers, torque to 63 ft-lb and again after about 100 miles.

Best,
Grady

Grady,
Thanks for your reply. I was hoping you'd see this thread. I have studied the CV rebuild thread (a lot!). I plan to use new bolts and the correct washers etc.. You said in one, short sentence what it took me a paragraph in my original post to describe: that I was hoping to find out if the spline size inside the early 108 mm CV joint and the ‘late’ (928) 108 mm CV joint is the same. If nobody has the answer, I may just buy one to see if it fits and return it if it doesn't. Do you see any other "gotcha's" that I may not have thought about?

Thanks again for the help,
Tom

[Grady Clay]

Another important area here that I don’t know the answer is the length of the splines inside the CV joint and on the axle shaft? The '928' version, '69-'71 version and 930 Turbo version are axially ‘thicker’ than the ’72-’75 911 version.

For example: The 108 mm CV joints became axially ‘thinner’ in 1972. I don’t know if there was a corresponding change in the axle shaft splines length.

This is important when combining the ’69-’71 and ’72-’75 108 mm CV joint, the ‘928’ CV joint and even the 930 Turbo CV joints with the various axle shafts.
(The 930 Turbo axle shaft is much shorter than the 911 version.)
Is a 930 Turbo CV joint splines compatible with others?



Our 108 mm Lobro CV joints are very robust and long-lived if properly lubricated. In fact I consider them ‘fine’ parts in our 911s.

One of my good examples is my friend Dave with a 600+ hp SBC and huge Hewland in his 914. I gave him some used ’69-‘71 911 CV joints on 914-6 axle shafts in 1974. They are still perfect after decades of SCCA racing.

There are shops that rebuild Lobro CV joints to specs higher than original. I suspect these are a LOT more than $79.

I would want to inspect, measure and know some historical, reliability and longevity information about the current aftermarket parts. It may be that ‘good used’ OE Porsche parts are better.

Best,
Grady

[Joe Bob]

Another good source for parts, rebuilding and information is Eric at www.pmbperformance.com , both for brakes and CVs.

[Tom '74 911]

Originally Posted by Grady Clay

Another important area here that I don’t know the answer is the length of the splines inside the CV joint and on the axle shaft? The '928' version, '69-'71 version and 930 Turbo version are axially ‘thicker’ than the ’72-’75 911 version.

For example: The 108 mm CV joints became axially ‘thinner’ in 1972. I don’t know if there was a corresponding change in the axle shaft splines length.

Best,
Grady

Grady,
I had the same thought as well. My guess is that the splines on my '74 axle shaft are not long enough to accommodate a thicker CV. If I discover any answers, I will post back.

Thanks again,
Tom

[Grady Clay]

When I converted my 914-6 to the 108 mm CV joints from the ’69-’71 911, the length and size of the splines fit perfectly.
Keep in mind that even a 914-6 has the similar very small CV joints as a 914-4.
However, the 914-6 axle shaft splines are compatible with 911, the 914-4 splines are not.
(Same issue with front torsion bars. )

Best,
Grady

[Tom '74 911]

I thought I'd post a quick update. . .

I decided to purchase new 108mm, (6) 10mm bolt, G-50, w/end cap, CV joints to replace the inner CV's on my '74 axles. Here's the PN: 911-332-923-01-M60 and here's a photo from the Pelican catalog:



It looks like they will work in that the splines seem to be identical in their pattern as well as depth when compared to my '74 CVs.

So here's my entire axle assembly out to in:

'74 stub axle, '74 108mm outer CV (4-10mm bolts & 2-pins), '74 half shaft, G50 108mm inner CV (6-10mm bolts), G50 drive flange machined to fit in a 915 w/OS Giken LSD.

I haven't assembled everything yet, but it's looking like it will all fit together.

The only issue I am dealing with at the moment is the stiffness of the new CV joints. They are almost impossible to move by hand - is that normal? I posted in this thread about it as well: http://forums.pelicanparts.com/porsche-911-technical-forum/578737-cv-joint-issue-2.html#post5880613

Tom

[Grady Clay]

Tom,

Great.

What is the difference in profile of the old face that originally contacted the transmission axle flange with a gasket and the new face that contacts the end-cap?

Please post the axial thickness of the inner races of both old & new CV joints.

Does your axle use a conical spring washer?

What is the measured dimension on the axle shaft from the circlip grove to the seat?

How many splines?
What diameter? (This is a difficult measurement because of the splines.)

Please measure the axial thickness of the outer race of the CV joint.

Compare the ball diameter.

Post a comparison between the joints of the ability of the center of the CV joint to move axially.

When you have the transmission axle flange available, carefully inspect the clearances between the end-cap and the inside of the flange.
There are several ‘course-spline’ 108 mm flanges with various clearances for the cage, balls and inner race of the CV joint.


There are two reasons for all these questions:
First is finding the best compatibility for updating our 911s.
Second, Lobro-like CV joints are ubiquitous. I suspect we will see some cars with incorrect joints for the application. We need some idea of areas where compatibility is critical.

For example, what if your new end-cap doesn’t fit inside the transmission axle flange and there is no provision for a gasket. Do you just bolt-up the new joint without either a gasket or end-cap? Do you modify the end-cap? How? Do you machine provision for a gasket?
All important questions – hopefully not necessary.


Another important question about CV joint and axle splines is; what are the specification? Are these DIN, ISO, SAE, other? What specification size, number, etc? I can see some ‘third-world’ part being hawked and not properly fitting (‘fits-all’ clearance).

This is an area of replacement parts where almost every car in the world is using these CV joints. Some may have a wholesale cost sub-$1. I can see the temptation for some of those finding their way into our ‘parts stream’. Not good if they don’t work as expected.

Best,
Grady

[Tom '74 911]

Hello -

I had everything apart and accessible last week and took some measurements. The cliff notes version is that the 2 CVs ('74 CV w/(4) 10mm bolts and (2) pins and a late Carrera G50 CV w/(6) 10mm bolts) are almost identical. I have replaced the inner CVs on my '74 axle w/the later G50 CVs and while not yet installed in my car, it looks like it should fit.

Some things to note:

1. I'm sick of CV joints. I was going to type out a long summary of the work I did, the options I had and why I chose to do what I did, but I am burnt out! Maybe someday I will add more explanation - if you have any specific questions please ask.
2. Please take my measuring w/a grain of salt - ie: I'm not perfect.
3. The end cap on the G50 CV will NOT fit inside my '74 transmission output flanges. Note the difference in recesses in the pics below.
4. Note that I did have to mill the end of the G50 flanges to fit in the 915 diff.
5. I did have to modify the '74 end caps that the rubber boots fit onto to accept the additional 2 10mm bolts of the G50 CVs. This required drilling holes and some hammer work to create recesses for the moon plates to sit flush.

Here's some measurements and photos:

[Grady Clay]

Tom,

You are wonderful (even as a charcoal ember).
Good measurements and images.

Here is an image of two 108 mm flanges:
The flange on the left accepts the end-cap but is ‘fine-spline’.
The flange on the right is ‘course-spline’ but won’t accept the end cap.
In fact, I would be concerned about the cage/ball/inner race interference in some cases.






I am not convinced either way that there exists a flange with both course-spline and is compatible with the end cap.
I’m not so much concerned with the roll-pin issue as that can be converted to 6-bolt.
I recall flanges that have the cut-away part to clear balls, etc but I don’t know if an end-cap will fit.

The goal is to figure out how to convert 915s with 100 mm CV joints to 108 mm CV joints.

My personal effort is to additionally use the end cap.

How are you going to address the issue of the gasket if you don’t use the end-cap?


Take a break from CV joints.
Add a log to the fire.
Have an ‘adult beverage’.
Watch the snowflakes.
Think positive Porsche thoughts.
All is well.

Best,
Grady

[Tom '74 911]

Originally Posted by Grady Clay

Tom,

You are wonderful (even as a charcoal ember).
Good measurements and images.

The goal is to figure out how to convert 915s with 100 mm CV joints to 108 mm CV joints.

My personal effort is to additionally use the end cap.

How are you going to address the issue of the gasket if you don’t use the end-cap?

Best,
Grady

Thanks Grady -

As tired as I am of CV joints, I have taken so much from this BBS, I felt it my duty to provide some useful info here as a contribution to the well of knowledge.

Converting my rebuilt, fine splined diff. 915 to 108mm flanges was exactly my goal. And using the end caps where possible was a bonus for me too. It should make engine removal/install SO much easier to have those on the inboard (transmission) side. No more grease, gaskets etc.... I'm excited for that.

I will continue to use the typical gasket (no end cap) on the outboard (wheel) side CV to drive flange connection. This is an OK compromise for me as I won't mess w/that end much if at all for quite some time. Finding a cap to fit that end would be nice, but I don't see any obvious paths for that.

That's it for me and CV joints for a while (hopefully!). It is currently snowing, my fireplace (gas stove) is running and I almost always have positive Porsche thoughts - so 4 out of 5 isn't too bad! (I'm drinking tea not beer!)

Thanks,
Tom

[ttweed]

I did a search on '74 911 CV joints and came up with this thread, so I'm posting a question here for the experts rather than start a new thread. I have two half-shafts that came with a '74 915 transaxle basket case that are different in appearance. They are both the same overall length, and both have the 4-bolt plus 2-pin flanges:


However, the CV joint housing on one is visibly thicker than the other--about 1-1/4" versus 1-1/2" or so--on both ends:


I don't understand why they are different thicknesses--was one side replaced with a different assembly at some point, perhaps? I can see "Lobro" stamped in the thinner one, but can't find any similar marking on the other housing. Can anyone identify what I have here?
TIA,
TT

[Tom '74 911]

Hi ttweed -

I'm bumping this for you because I don't know the answer.

I think 930 CVs are thicker, but as an assembly, I think the whole 930 half-shaft is shorter. Maybe someone put 930 CVs on a standard '74 axle? I'm not sure that would actually work though (already contradicting myself) as the splines on the axles are only so long & I don't know if a thicker CV would even fit on a standard axle. . .

As I said, I don't know the answer. . . bump!

Tom

[Trackrash]

It's my understanding that the thicker CVs are from a '70-'71. For '72 Porsche went to the updated "lightweight" and thinner CVs.

I ran across this issue when I upgraded my '71 to a 915 trans recently.

I believe the axles are a different length as well?
You will notice there is a difference between the '71 axle flange and the '72 flange.



I just ran across this thread and thought a bump was in order.

[ttweed]

Thanks for the info, Gordon. I didn't know that they changed to lighter weight, thinner CVs in '72. The axles definitely must be a little shorter on one side, because the overall assembly length is the same. I haven't taken them apart yet, as I figured I'd just sell them, since I doubt I'm ever going to need them myself.

Hope you're doing well up north--we miss you down here in Lo Cal.
C'ya,
TT

[Hcarraro]

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[ronw]

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i'm having '72 lwb trailing arms modified to work with swb narrow body. trying to figure out what i'll need in terms of axles and transaxle output flange for my 901