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CV Constant Velocity Joint & Fastener Compilation - Schnorr Belleville

I thought I'd do a little CV joint compilation. I stripped out the names of most posters - I left in Warren & Jim Sims because of their backgrounds and experience. I added some ?? when I didn't understand a comment. Feel free to post additionally on top of this. I hope this is helpful. I've had these things out 3x in 2 years for one reason or another ans still don't remember all the little tricks w/o notes. - Randy
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There should be 4 high strength (12.9) 10 mm socket head cap screws and two roll pins ("Spirol" type) securing each CV joint flange to the corresponding flange on the transmission final drive or the wheel hub assembly. There are lower strength metric socket head screws available; do not use these. If you replace the screws get 12.9 grade.
There should be a single treated cardboard type gasket between each flange set to keep road debris out of the CV joints.

The screws should be installed with the threads unlubricated and tightened using a torque wrench to 60 ft-lbs. Clean out the female threads as required in the mating flange on the tranmission final drive or the wheel hub assembly (can spray brake cleaner). The hex inside the screw head should be 8 mm but some screws require a 12 point triple-square drive bit.

There should also be a curved, arc shaped washer plate under and spanning between each pair of screws and a "Schnorr" type lock washer under the head of each screw. Schnorr lock washers have a dished shape with serrations on both sides; ---> the concave side of the dish goes towards the washer plate. <----

Schnorr washers should be replaced -- not reused. Clean out and inspect the screw heads throughly before attempting to tighten; if the the hex sockets in the heads show signs of rounding replace the screws (Pelican sells them). You can reuse the crescent shaped locking plates.

If the car has been outside in the weather I'd check the inside of the loose flange for dirt and water. If there is only minor dust I'd wipe it and reinstall. If it's wet and dirty I'd clean and repack the CV joint and consider replacing the boot. If the maintenance history of the car is unknown you might consider just replacing all four boots and clean and repack all the CV joints or at least consider doing it in the near future. There are past threads complete with images on how to take apart and reassemble the CV joints and half shafts, including a post of repair manual pages (from Warren, EarlyS_Man? that are now unavailable). Also see the book "101 Projects". I think Pelican sells everything you might need in the way of parts, tools and lubricants (?? what lubricants - installed dry).
-- Cheers, Jim Sims

You can drill the bolt head for safety wire or you can get 12.9 socket head screws with holes already made in them from aircraft parts places (A/N grade screws). Some say the holes are drilled, but it is not clear when that is done in the manufacturing process, so they might be stronger than ones you drill at home, and are surely easier than drilling a small 12.9 bolt head.

Note that using Loctite will alter the frcition/torque/bolt tension relations, so you will not get the correct torque. A favorite trick (torquing and then adding the green, wick-in Loctite) won't work as there is not space to do that here.

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If you have the updated Lobro axle you can not use the old bolt on both ends. The updated axle is not as thick as the original It has sheet metal covers that require the two bolt plates that displace the pressure from the bolt heads against the sheet metal. you can use the 50mm bolts on the trans end of the axles but you have to use 45mm bolts on the wheel end to prevent the bolts from protruding too far through the flange. Make sure the threads are clean and dry before you torque everything down to 31-ft lbs and it would not hurt to use Locktite.{see note above}

You do not need Schnorr washers and there are no extra gaskets.

Jim Sims: Mussberger is right; Technical Bulletin 5 in the Parts and Technical Reference catalog 1974-1989 covers this. You need washer plates PN 911.332.191.00


Schnoor Washers:
always replace these. Pelican carries them individually, e.g. K-523-103-01 or J-027-015-02.
Schnorr is actually the manufacturer, not necessarily the type of lock washer. They're also sometimes called Belleville washers.

Best description of them is at Metric and Multistandard Components Co.
Disc Springs
Ribbed/Serrated Springs

You can view the whole catalog by going to
http://www.metricmcc.com/index.htm

and then clicking on the little red book icon on the left sidebar.

McMaster-Carr carries the Belleville washers, but the metric selection
isn't as good.

www.mcmaster.com

and type in "belleville washer" in the command line @ the top left of the page.


from PET, for a 1973 use either
M10x48 900-067-128-01
or
M10x55 900-067-087-01
{check the difference by measuring the shaft length exclusive of the screw head}

Schnorr lock washers
999-523-103-01

locking plate- the crescent shaped thing
911-332-191-00

Last edited by Randy Webb; 08-18-2004 at 08:54 PM..
Old 08-17-2004, 08:14 PM
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Awesome post, Randy! Thanks for the research!

I do humbly request some clarification, however. My car is an '86, and as I understand the axles from 84-89 were identical:
1: If my axles say "lobro" on them, I shouldn't have the magic lock washers?
2: "treated cardboard gasket?" Is that a gasket between the thin dust cover over the axle and the differential output flange?
3: 60ft-lbs applies to the 6 hex bolts that hold the CV joint onto the diff flange, right? I assume it is common practice to use an allen socket and torque wrench for this job?

Thanks in advance; again, excellent post.

Dan
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Old 08-17-2004, 09:25 PM
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yes on #3. I hope Jim will post re #2 Check that tech article for #1 (or the PET - it is usually correct).
Old 08-17-2004, 09:59 PM
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#3 was the gimme, Randy!

I don't happen to have a PET. (smartypants) I mean, my room-mate has a dog, but she doesn't know anything about Porsches. I hope someone with a PET who knows something about Porsches responds. (/smartypants)

Thanks,

Dan
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Old 08-18-2004, 05:28 AM
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Hey, if you have SIX bolts, aren't they 8mm? Which would be a lower torque spec than 60 ft/lb, right?

I would add that you want the Belleville washers curved side inward when you install them.
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Old 08-18-2004, 05:38 AM
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Axles are not the same for 84-89.

Late 84/mid year 85 changeover to different bolt cirlcle diameter ( 108 vs 100 mm, I believe). Early 85 was last of demountable end at wheel. Later year had friction-welded ends on wheel side.

See Driver8 comments here...
Rear Driver side axle nut coming loose

60 ft-lbs is only correct for these years for the larger Turbo or Turbo look bolts. Smaller normally-aspirated cars use something like 38 ft-lbs

---Wil
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Last edited by Wil Ferch; 08-18-2004 at 06:36 AM..
Old 08-18-2004, 05:52 AM
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Quote:
Originally posted by djmcmath
Awesome post, Randy! Thanks for the research!

I do humbly request some clarification, however. My car is an '86, and as I understand the axles from 84-89 were identical:
1: If my axles say "lobro" on them, I shouldn't have the magic lock washers?
2: "treated cardboard gasket?" Is that a gasket between the thin dust cover over the axle and the differential output flange?
3: 60ft-lbs applies to the 6 hex bolts that hold the CV joint onto the diff flange, right? I assume it is common practice to use an allen socket and torque wrench for this job?

Thanks in advance; again, excellent post.

Dan
Like Wil said, your '86 doesn't have the Schnorr washers. Only a small plate between the screw head and the CV joint. #14a below.



No paper gasket either on the '86 axle. I know the above diagram shows #13 as a paper gasket. But the side comments call out the gasket being used for 915/67 and 915/68 trans. models. These are said to be the trans. used in 84 & 85, with the pre-85.5 axle assemblies.

The 30 vs. 60 lb-ft torque spec has been argued before. I'm pretty sure the 30 spec. is for the M8 screws and the 60 is for all of the M10 screws (NA and Turbo cars). I think the tiny Porsche 84-87 spec book is incorrect here. When this issue came up before, I checked against my microfiche repair manual for 84-89 cars and i'm quite sure it stated 60 for the spec.
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Last edited by KTL; 08-18-2004 at 06:58 AM..
Old 08-18-2004, 06:55 AM
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The 30'-ish spec is correct for the 8mm...the 60 ft-lbs is correct for the 10mm.

If you wish to "triangulate" to the correct answer...these torque values not only match well with most ( not all!) Porsche text...but these values follow general fastener recommendations when viewed simply on the basis of size....

--- Wil
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Old 08-18-2004, 07:01 AM
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The gasket use is confusing. I installed the gaskets on the very ends of my 86 turbo axles, and every bolt came loose within 200 miles. I had reused the old bolts. Deman Motorsports snickered at my use of the gaskets when I got towed to his shop, but I was going by the Porsche shop manual picture which shows them so how was I to know... he removed the axles to remove the gaskets, and then put 60 ft lbs on new bolts.
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Old 08-18-2004, 07:54 AM
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(mildly confused, but clearing up) So in 85-89 cars (roughly), it's no Schnorr washers and no paper gasket. It's also a bigger diameter axle (108mm?) with no castellated nut/cotter pin. Torque spec on that axle end-nut is still 339ft-lbs, and should still be re-specked after a day of hard driving.

The number and size of CV-DOF (Diff Output Flange) bolts seem to vary from car to car, based on what the PO has done with it, yes? It looks almost like the consensus is 30ft-lbs for the smaller (6 in number) bolts, and 60ft-lbs for the larger (4 in number) bolts. Are those reusable?

Thanks again, all. Excellent thread!

Dan
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Old 08-18-2004, 09:23 AM
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Turbo ones..the big ones using 60 ft-lbs....use ( I believe) 6 , not 4....just to add to the fray !!

---Wil
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Bolts are reusable if in good shape - see the quoted JS post at top.

But if they are 30 years old it is no biggie to just replace them.
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Roger all that, thanks a heap. If only I could read, I'd spot these things.

Dan
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Old 08-18-2004, 02:13 PM
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Schnorr lock washers are a type of Belleville washer but Belleville washers are not Schnorr washers. The ribbed or serrated washers sold by Metric and Multistandard Components are Schnorr lock washers. I do not know of anyone else who manufactures them other than Schnorr. Schnorr washers are one of the few really effective, easy to install, lock washers (with testing to prove it) but they cannot be used with a regular bearing washer; they must be used with a washer or washer plate that cannot rotate (such as the c-shaped washer plate used in the CV-joints) or directly between the head of the fastener and the non-rotating item to be secured.

The gaskets used to seal the interface between the CV joint flanges are there to seal out water and debris from the internals of the CV joints. They are a potential source of loss of screw pre-load if they compress, so it is wise to recheck the CV screw torque 100 miles or so after intitial installation. My personal experience has not shown any problem using the gasket where Porsche used them in the OEM configuration. I suspect the loose CV joint screws are more likely a problem of improper torquing as the repair literature errors and the many CV-joint configurations appeared to have sown much confusion.

I do not believe the fastener heads are weakened in any practical sense by drilling in the wrenching section for lockwire use.

Cheers, Jim
Old 08-18-2004, 05:26 PM
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Thanks Jim.

What was the carboard reference in your earlier post (just a way to explain the corrugated nature of the Schnoor washers?)

Do you think that folks replacing the bolts should spray out the female thread area with brake cleaner?
Old 08-18-2004, 05:39 PM
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The 'paper/cardboard' gaskets aren't actually paper, or cardboard ... unless a cheap counterfeit! The OEM factory gaskets I have seen and used for decades probably contained asbestos at one time ... because I have seen them referred to as 'graphited-asbestos.' There are asbestos-free alternatives, now, containing Kynol, Kevlar, Teflon, and other exotic materials, bonded together by vulcanizing or other processes ... just as for intake manifold-to-head gaskets, but simple cardboard gasket material is not likely to be a satisfactory substitute for the OEM gasket material!

I suspect that the 'loosening' phenomenon is not likely with OEM gaskets, because they don't have any significant compressibility!
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Old 08-18-2004, 06:15 PM
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Although the gasket between CV-joint flanges may look like cardboard it is a special, water proof, high density composition. The serrations in Schnorr washer are upset; the washers are not really corrugated (as in folded). Clean thread holes are a good idea; just keep the brake cleaner out of the wheel bearings. Jim
Old 08-18-2004, 06:26 PM
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According to the factory workshop manual the torque spec for M10 bolts in the turbo is 60 ft. lbs.
Quote:
Torque spec on that axle end-nut is still 339ft-lbs
Manual lists this as 217-231 ft. lbs.-again for the turbo. Also this nut is only 30mm on the turbo, not the 32mm commonly found on NA cars.
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Old 08-18-2004, 08:49 PM
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OK, I made a few edits to the initial post in this thread -- mainly to help folks who find it later on. Post #1 is not intended to be a complete DIY guide tho.....

Last edited by Randy Webb; 08-18-2004 at 09:18 PM..
Old 08-18-2004, 09:10 PM
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Beautiful work, Randy. Thanks for the compilation!
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Old 08-18-2004, 09:36 PM
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