Reconstructing Constant Velocity (CV) Joints

[ClickClickBoom]

Bump!

[seafeye]

Originally Posted by rcecale

Randy,

If there's a way to repair my CVs, I'm all eyes!

I've got the newer axles, with the outboard CV incorporated into the stub axle. I don't believe these are repairable.

My axle:


I know I can replace the inboards, but the outboards, from what I read, if they are worn, require the replacement of the whole axle.

If you know of a way, do tell. It's gotta be cheaper than new axles.

Randy

DC power!
This is the tool you want. 700 ft lbs of torque.
Will easily take off stubborn axel bolts. I’ve thrown away all my air tools and gone cordless. Only thing I miss about not having an air compressor is being able to blow air to clean my car.

[ClickClickBoom]

From AC 43.13-1B for questions about safety wiring CV bolts:
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.13-1B_w-chg1.pdf
This is the bible for aircraft mechanics when a manufacturers maintenance manual is not available.
9/8/98 AC 43.13-1B
SECTION 7.
SAFETYING7-122.
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.

[RWebb]

pal nuts??

good sleuthing on the Aircraft manual

[ClickClickBoom]

Originally Posted by RWebb

pal nuts??

good sleuthing on the Aircraft manual

I carried a paper copy in my toolbox for 25 years. Feds on the ramp or building see a paper copy on the tool box, just move on to easier prey. PDF is nice on the iPad.

[2jmotorsports]

So what length M8 bolts are people running on 100mm CVs with the lock plates and Schnorr washers (inners and outers)?

[Quasimoto]

Originally Posted by 2jmotorsports

So what length M8 bolts are people running on 100mm CVs with the lock plates and Schnorr washers (inners and outers)?

Something I learned while doing mine is to measure your stack rather than relying on an answer to that question. There can be differences in joint and boot flanges that make the stack slightly different. YMMV

[2jmotorsports]

Fair enough. Thanks for the feedback!

[hienz]

Needed one new cv boot for my 75 911s, which brand should I buy? I like the original CV boots in my car right now.

[mxtx]

read this entire thread and ended up with (12) M10x55 + 3 stacked Belleville Washers over Moon Plates.

Based on bolt length comparison I’m anticipating 1-2 threads poke. However, I have not completed assembly due to stripping the flange upon reassembly.

1985, 915/73 tranny, w/LSD, 108mm axles, 6 bolts inner, welded stub axle outer.

going to try and tap it first, assess, reassemble... if it feels positive, i will monitor closely.

if it doesn't feel positive, is replacing the flange my next choice? has anyone experienced this?

any advice on how to better line up the axle to the flange on reassemble would be appreciate as well since that's how i stripped it in the first place…

the car is on stands and pulling the motor/tranny is beyond me at the moment fyi.

thank you all.

[Rawknees'Turbo]

Originally Posted by mxtx

read this entire thread and ended up with (12) M10x55 + 3 stacked Belleville Washers over Moon Plates.

Based on bolt length comparison I’m anticipating 1-2 threads poke. However, I have not completed assembly due to stripping the flange upon reassembly.

1985, 915/73 tranny, w/LSD, 108mm axles, 6 bolts inner, welded stub axle outer.

going to try and tap it first, assess, reassemble... if it feels positive, i will monitor closely.

if it doesn't feel positive, is replacing the flange my next choice? has anyone experienced this?

any advice on how to better line up the axle to the flange on reassemble would be appreciate as well since that's how i stripped it in the first place…

the car is on stands and pulling the motor/tranny is beyond me at the moment fyi.

thank you all.

If you use an actual tap on the hole with the damaged threads you will remove too much metal and the original sized bolt will not have much to clamp with/against.

Are the threads just damaged some or are they gone altogether? If damaged, even fairly significantly, you are better off running a thread chaser through it. You can even make one using a bolt with the same dimensions and thread pitch as the CV bolts. You do this by cutting a couple of shallow valleys the length of the threaded portion of the bolt, perpendicular to it. A thin cutting wheel on a die grinder or Dremel works great for this, or a file can be used (works, but much slower process). If you google, "homemade thread chaser" you'll find many pics of what I'm talking about. I've saved some pretty chewed up threads this way.

[mxtx]

thanks rawknees.

luckily the stripped part was just the very beginning, almost more of a burr than a full strip. was able to get past it smoothly with a regular tap and didn't have to go too far.

new axles are in now – will check-in after 100 miles for re-torque and will monitor to see how the everything performed.

4 washers was closer to flush with original 50mm bolt but decided to go with 3 thinking a few threads past is better than a few threads short. 60 ft-lbs each bolt. M10 bolts and washers from mcmaster carr. moon plates and 108mm axles genuine porsche.

[2jmotorsports]

Hi Contributors,

I plowed through this CV joint rebuilding thread as I am installing rebuilt CVs on my 83 SC. They have 100mm joints, with new M8 bolts, VW lock plates, and Schnorr washers. My only question is if anyone knows where the 33 ft-lb torque spec came from?

https://forums.pelicanparts.com/porsche-911-technical-forum/222537-reconstructing-constant-velocity-cv-joints.html#post1922501

My copy of the Bentley has conflicting values. Also cross-referencing generic torque spec tables such as this one from Fastenal list 12.9 M8 bolts installed dry at a max torque of 31.4 ft-lbs.

https://www.fastenal.com/content/feds/pdf/Torque-Tension%20Chart%20for%20Metric%20Fasteners.pdf

I am by no means saying 33 is wrong, its just very difficult to find objective data listed anywhere and some of the online sources such as Fastenal may simply be trying to stay conservative. I checked my Machinery's Handbook and only found dimensions and strengths but no torque chart for different grades.

Thanks again for the advice. I wonder if the original post can still be edited to contain summary info with references, like the CIS for Dummies thread.

[Walt Fricke]

Jose
The "little white spec book" Porsche published for the 3.0s gives 42 newton meters for these 8mm grade 12.9 bolts. That's 31 pounds/feet.
Me, for some reason I got 32 lbs/ft in my head, so that's what I do.

Don't overthink this. This isn't a disk drive (pre-solid state). You'll see various numbers. How accurate is your click stop torque wrench?

This is sort of like lug nut values - I torque to 92 lbs/ft with my old torque wrench. Nothing is going to break at 95, or fall off at 90.

[2jmotorsports]

Originally Posted by Walt Fricke

Don't overthink this. This isn't a disk drive (pre-solid state). You'll see various numbers. How accurate is your click stop torque wrench?

Good point. Its my job to overthink everything, precisely so that things dont fall off. Its difficult to flip that switch in my head to the OFF position sometimes.

[Kraftwerk]

Just to keep this thread alive with more information: I think the Schnorr site specifically says NOT to stack the washers, better to trim the bolts, use flat washers etc.

[ClickClickBoom]

31 lbft is danger close to the yield point for 8mm 12.9 bolts, as per industry documentation and the Nordlock engineer. This is evidence of how critically designed this bolting solution is, and the necessity of proper procedures for assembly. 31 lbft is the number, not 32 or 33.

Originally Posted by Walt Fricke

Jose
The "little white spec book" Porsche published for the 3.0s gives 42 newton meters for these 8mm grade 12.9 bolts. That's 31 pounds/feet.
Me, for some reason I got 32 lbs/ft in my head, so that's what I do.

Don't overthink this. This isn't a disk drive (pre-solid state). You'll see various numbers. How accurate is your click stop torque wrench?

This is sort of like lug nut values - I torque to 92 lbs/ft with my old torque wrench. Nothing is going to break at 95, or fall off at 90.

[ClickClickBoom]

Spring is coming, bump for everybody with project plans!

[Sajan]

Based on my readings (here and sourcing the service manual):

Axle Shaft (1985+ -- 108mm), + moon plate
M10 x 50mm - 12.9 - 83 Nm (60 ftlb)
M8 - 12.9 - 42 Nm (30 ftlb)

Is this accurate?

I wonder where I can find some Schnorr washers locally.

[ClickClickBoom]

Originally Posted by Sajan

Based on my readings (here and sourcing the service manual):

Axle Shaft (1985+ -- 108mm), + moon plate
M10 x 50mm - 12.9 - 83 Nm (60 ftlb)
M8 - 12.9 - 42 Nm (30 ftlb)

Is this accurate?

I wonder where I can find some Schnorr washers locally.

The moon plate was not stock, so you have to do a stack up and measure. Measure the flange, then the CV/dustboot, moonplate stack up, add up the totals and there ya go. I get my bolts from Belmetric and I use Nordlock NLX washer system.
Use an accurate torque wrench on the 8mm bolts, 30 lbft is danger close to the engineering design limit.