CV Axle Questions

[Steam Driver]

I have searched the threads on this and I know there is a wealth of information out there but I couldn’t sort out what I needed.

First, I have on hand the hardened Schnor washers. They are dished. Does it matter which way the dish faces?

Second, I am adding the half-moon plates which my SC never had. This obviously takes up some bolt length. Do I need longer bolts to accommodate this? Current bolt is M8X50. The half-moon plate is 2.5mm.

Third, I need to replace at least three of the bolts for questionable index condition. What grade are these bolts? Is the recommendation to replace all of them? I’ve seen mixed opinions on that. (As well as the half-moon plate issue.)

[donbecker1234]

Sort of related but not directly answering your questions, I recently did my CV’s and swapped the stock bolts and moon clips for locking fasteners as I’d heard of them backing out on folks.

https://www.stage8.com/product/8327-cv-joint-bolt-kit-10mm/

I used the 50mm.

They were expensive, but when I was unbolting and found some of the stock bolts not tight...I felt somewhat justified.

[Dave Colangelo]

Anytime I do the CV joints i replace all the bolts, there is just to much of a risk in striping those heads and causing a headache down the line, its worth the piece of mind considering the fairly low cost of a new set. If you get them from our provider here they will be the proper grade.

I dont think the half moon plates require anything more than the standard hardware. (at least ive never used anything but standard hardware on my SC)

Schnor washer installation discussion can be found here but keep in mind you can only use them once so if you torque them down and need to open them up you should get fresh washers.

The key to reliable CV joint bolt installation is to torque properly in a star pattern, un-even torque is often what causes bolts to back out.

Regards
Dave

[winders]

The Stage8 fasteners are just as good as safety wire in this application. In other words, there is no benefit as clamping force is key here and the Stage8 fasteners can back out far enough to lose the clamping force...just like with safety wire.

[bkreigsr]

Originally Posted by winders

The Stage8 fasteners are just as good as safety wire in this application. In other words, there is no benefit as clamping force is key here and the Stage8 fasteners can back out far enough to lose the clamping force...just like with safety wire.

I don't see how that's possible if the bolts are torqued correctly to 49 ft lbs.
So if the bolt backs out one indent on the washer, you are maybe down to 30 ft lbs of torque , or there abouts.

Read Walt's comments here:
Trans experts. 923 CV joints

[winders]

Stage8 will keep the bolts from backing out.....but they do not guarantee that the proper clamping force will be maintained.

[Solamar]

Stage 8, Schnorr, Nord-Lock, moon plate, naked, whatever your poison make absolutely positive that your bolts are long enough to slightly protrude out the back of the flange. Even different boot flanges have different thicknesses. You have to measure, don't guess.

FWIW my poison is Nord-locks.

[bkreigsr]

For those who are interested, here's how my Stage 8 fasteners turned out after today's install

(Of the 12 OEM inner bolts I removed, 8 were stripped to the point where they would not hold any torque at all.)

Several books/manuals I have indicate a final torque value of 42 ft lbs. That is wrong. ARP lists the correct between 24 and 32 ft lbs. for a M8 x 1.25 x 50 mm, made of 4130 alloy, class 12.9.
I settled on 25 ft lbs or 300 in lbs.

The higher number in the factory manual probably explains the 8 stripped bolts.

Bill K

[winders]

25 ft-lbs is not enough to get the proper clamping force. 30 ft-lbs is barely enough....I would suggest 33 ft-lbs.

[bkreigsr]

Thanks for your opinion,
.......but 25 ft lbs is plenty for this particular bolt in this application.
sources:
https://www.futek.com/bolttorque/metric

https://arpinstructions.com/generaltorque.html

[winders]

I don’t think you understand that a CV is a friction-type joint and not a bearing-type joint. A friction-type joint depends on the clamping force of the bolts to maintain the integrity of the joint.

The 8mm bolts only have enough clamping force if they are torqued correctly. 25 ft-lbs has 17% less clamping force than 30 ft-lbs and 24% less than 33 ft-lbs.

Really, 25 ft-lbs is not enough!!

[winders]

Your ARP links assumes you are using ARP bolts with their lube. I don’t know what that other link says because I have no idea what you entered.

CV joints are assembly without lube on the bolts or the mating surfaces.

[ClickClickBoom]

Originally Posted by bkreigsr

Thanks for your opinion,
.......but 25 ft lbs is plenty for this particular bolt in this application.
sources:
https://www.futek.com/bolttorque/metric

https://arpinstructions.com/generaltorque.html

Not true, this is a critical friction joint. Porsche specifies 42 Nm or 30 lb ft. According to the Nordlock fastener engineer this is very close to 12.9 bolting absolute torque.
Read the Reconstructing CV thread. There is maybe 1 hour of stuff, most really good.

Reconstructing Constant Velocity (CV) Joints



I was lazy on the torque, and lost a cv going to work, it was very nerve wracking. This is not one to fudge on, like brakes.
P.S. the amount of rotation between 25 lb ft and 30 is almost imperceptible in rotational movement. Safety wire or Stage 8 washers will not prevent loosening, proper assembly and torquing will, don’t forget settlement either. I use Nordlock NLX, these bad boys are crazy good, and reusable.

[bkreigsr]

Okay, so I used 25 ft lbs instead of 30 ft lb (imperceptible).

On the plus side, all my dental records are up to date, so they won't have any trouble identifying my remains after the pull my corpse from the twisted wreck.

Nordlocks NLX would have raised the bolt head at least 2 mm. A 8x50mm bolt comes just flush to the rear of the flange. With the Nordlock NLX I would end up having to stack washers under a 55mm bolt to get the proper penetration into the flange. What happens to the griping ability of the Nordlock NLX washers when you stack with more Nordlock NLX washers, or plain, or split-ring lock washers?

As far as I know the only way to get bolt between 50 and 55mm is to have it custom made.

But, I still need one of the experts to explain to me how a Stage 8 fastener (bolt+washer+snap ring) can come loose. (Preferably, an expert that actually has experience with them.)

[winders]

25 ft-lbs give you 17% less clamping force than 30 ft-lbs. That is in no way "imperceptible". That is actually a large difference for this joint type. 12.9 M8 bolts used in this application are fine at 36 ft-lbs. The Factory manual recommends 30-32 ft-lbs. In this application I would certainly pick the higher number as you want as much clamping force as possible. In fact, 33 ft-lbs is perfectly safe to use and provides a bit more clamping force. 25 ft-lbs is 24% less than 33 ft-lbs.

Why I am harping on about clamping force? If you don't have enough clamping force, the joint will move and this movement causes the bolt to slowly loosen. The more the bolts loosen, the more movement there will be in the joint and the more the bolts will loosen. 8mm bolts properly torqued are really quite borderline on keeping the Porsche CV joint from moving which is why you have a market for third-party kits that claim to solve the problem. Safety wire or even your Stage8 kit won't prevent bolts from backing out slightly. They will prevent them from backing out completely. But then you are starting to rely on the shear strength of the bolts and that is a losing proposition. The M8 bolts are not strong enough in shear to prevent a failure.

Massively increased clamping force is why you see far less problems with the 10mm bolt CV joint setups. The clamping force is so high that you rarely get joint movement. I have never had a 10mm CV joint bolt loosen on my race car which is a far more severe application than a street car.

[winders]

This is what you have to look forward to if the bolts shear off:

CV Joint Failure Carnage

[ClickClickBoom]

Originally Posted by bkreigsr

Okay, so I used 25 ft lbs instead of 30 ft lb (imperceptible).

On the plus side, all my dental records are up to date, so they won't have any trouble identifying my remains after the pull my corpse from the twisted wreck.

Nordlocks NLX would have raised the bolt head at least 2 mm. A 8x50mm bolt comes just flush to the rear of the flange. With the Nordlock NLX I would end up having to stack washers under a 55mm bolt to get the proper penetration into the flange. What happens to the griping ability of the Nordlock NLX washers when you stack with more Nordlock NLX washers, or plain, or split-ring lock washers?

As far as I know the only way to get bolt between 50 and 55mm is to have it custom made.

But, I still need one of the experts to explain to me how a Stage 8 fastener (bolt+washer+snap ring) can come loose. (Preferably, an expert that actually has experience with them.)

If you are dead that's the only concern. Most likely the flailing driveshaft will trash a bunch of expensive parts, up to and possibly including the transmission case and exhaust.
What needs to be asked is why Porsche spec'd 30 lb ft. for the torque when, that is when engineering specifications put that close to design limitations for a 12.9 bolt.
The difference between 50 and 55mm bolts is minimal, 5 mm to be exact. On my car I could have used a significantly longer bolt without issue, I use 55mm bolts with Nordlock NLX washers. I have spent a long time under the car replacing boots and CVs.
Stage 8 fasteners are a great product, for the right application. This is not one of them, neither is safety wire. Correct torque, causing proper bolt stretch and therefore tension is what is critical. If you can stretch con rod bolts and not have any locking devices or thread lockers. Proof that proper torque and bolt stretch is enough. I noted in previous posts, that I stage torque, 25 lb ft then 31 lb ft for the finish. Then recheck after 3600 seconds for settlement. The rotational torque from 25 to 31 lb ft is almost imperceptible ie a degree or two, but make no mistake, there is a difference. I am not a strict "originalist", I am a strict engineerist, and the torques are very close to engineering max specs for 12.9 bolts.
If your car is a garage queen or you don't really drive much then 25 lb ft might be OK. Push the car a little and it MIGHT, work or it might not.
Not trying to be trivial, but I was bitten by the casual assembly monster, and lost a CV with minimal destruction, my SSIs took some abuse as well as the surrounding parts. Ignore/minimalize at your own peril.
Fastener technology, while not nearly as fun as MFI or turbo flares is even more critical than many imagine. The majority of bolted joints are well below the design limitations the ones that are close(this one) rely on proper assembly techniques.
BTW, I have been an Aircraft mechanic holding an A&P certificate and worked in the field since 1992. My info comes from FAA Advisory Circular AC43.13-1B Chapter 7 page 7-5 for bolts, and 7-122 for safery wiring:

7-122.

"GENERAL. The word safetying is a term universally used in the aircraft industry. Briefly, safetying is defined as: “Securing by various means any nut, bolt, turnbuckle etc., on the aircraft so that vibration will not cause it to loosen during operation.”
These practices are not a means of obtaining or maintaining torque, rather a safety device to prevent the disengagement of screws, nuts, bolts, snap rings, oil caps, drain cocks, valves, and parts.
Three basic methods are used in safetying; safety-wire, cotter pins, and self-locking nuts. Retainer washers and pal nuts are also some- times used."

Stage 8 system falls into this category.

[bkreigsr]

.....which brings up another question for the experts.

What are the graduations on you 3/8 " torque wrench?
How often do you get them calibrated and certified ?
What is an acceptable range of variation ?

Are the HB wrenches the same quality as the Snaps and CDI's ?

.....just wondering.....

[eastbay]

Let us know how it works out. I almost lost a CV joint on an off topic car years ago, but the noise from the loose joint alerted me to the issue before it was a problem. I am wondering how someone can ignore the clunking and banging of a loose joint before it lets go.

[ClickClickBoom]

Originally Posted by eastbay

Let us know how it works out. I almost lost a CV joint on an off topic car years ago, but the noise from the loose joint alerted me to the issue before it was a problem. I am wondering how someone can ignore the clunking and banging of a loose joint before it lets go.

Mine went from accelerating out of a corner with no noise to redline in a second. Failure modes can be almost limitless. Haven't had a problem since, and I drive alot.