Reconstructing Constant Velocity (CV) Joints

[rcecale]

Rick, I must have just missed your post before I left work. Really wish I'd have seen it. I'm pretty sure I have this software on one of our servers at work. Could have (and WOULD have) stayed late just to make these files available to everyone.

If you have the files and want to e-mail them to the above address, I can VPN into work and download the drivers for an HP OfficeJet 600. This should do the trick.

Randy

[RickM]

Randy, As long as you have Jet Suite Pro it should work.
I installed a large all-in-one package from a new HP MFM here at the office and it didn't fly.

I'll try at home and send the file to you now.
I'll also send the package software to Grady (if he wants) for future use.

[rcecale]

Grady, Rick,

I was able to open the .JSD file you sent me. Found a program called eFax Messenger that worked like a champ.

Using eFax, I saved the .JSD as an .EXE which includes a small viewer, incorporated into the file. You can open it on any computer running Windows, just like it is.

If anyone else wants a copy, PM me and I'll send it right out.

Randy

[rcecale]

I now have Grady's document in .PDF format if anyone else is interested.

Just send me a PM.

Randy

[}{arlequin]

ok, just to clarify some things...

I have the 10mm bolts which will need replacing. They are installed w/ the moon plates, but I do not see the schnorr washers there. Everything fits well, but I have no idea what length of bolts to replace them with.

I don't have the facilities where I can just pull one out and measure while the car just sits there, so when I get in there, I'm going to have to get it done and move on.

To prevent a holdup, I'm going w/ the shotgun approach of getting 45mm 50mm and 55mm bolts, M10, 1.5 thread, 8mm hex. McMaster-Carr under the 45mm bolts has a choice of full thread or partial thread on the bolts. The 50mm and 55mm only come w/ partial thread. Is full thread an improvement or does it actually weaken the bolt?

thanks.

edit: can, or SHOULD, these be made from stainless?

edit 2: are the washers serrated on both sides or just one?

[randywebb]

weakens - but I wouldn't worry too much about it

[ianc]

Regarding the inner clamps for the CV boots and the special pliers needed to properly crimp them: I've always discarded those damned things in the past and just used largish zip ties clipped off near the boot. Don't get them too tight, but enough so the boot can move a little. Not much motion there, so they last a long time.

ianc

[rcecale]

Originally posted by randywebb
what's in those '10 pages in a Factory workshop manual' and what years do they relate to?

Randy,

My humblest apologies.

I haven't been back to this thread for a while and am just now seeing this question. I was able to convert the file over to a .PDF you can open with Adobe Acrobat Reader. If you like, I can e-mail you a copy of it so you can see for yourself. The file is on my computer at work, but I can access it from here if you want it. No problems.

Randy

[jpahemi]

Grady:
I've been reading this thread wondering if I should re-pack my CV's. I've got an early 84 with the M8 50mm bolts with the 923 paper gasket on the ends. My CV's don't have the end cap & seperate from the axle flange (no friction weld there). Can this cap be installed as an upgrade and is it placed on both ends of the axle (axle & tranny flange)? Does the end cap replace the paper 923 gasket?
Regards,
J.P.

[Grady Clay]

J.P.

I’m glad this thread got resurrected; there is still much detail to post.

To answer your question in a word – no. The end cap requires a different flange at both the stub axle and transmission flange ends. There are two points of contention. First the clearance dimples in the cap don’t clear the mating shape of the flanges and stub axles – there is interference. Yes, you can carefully Drimmel away clearance in these parts but it is way too much work for any return.
The other issue may come back to bite us. The CV or flange is relieved to accept the gasket. There is a completely flat surface (no relief) when the end cap was used. This changes the clamping pressure given the same torque on the bolts. The end cap also inserts an intermediate piece of steel between the CV and flange. I can’t tell you if the net result is to improve the clamping and reduce the likelihood of a CV bolt loosing its clamping or not. Paging Jim Simms.

It is a simple process to replace the CV boots, clean & re-grease, and assemble with new gaskets, CV bolts and Schnorr washers. The devil is in the details, ask Randy. Most (but not all) has been covered in this thread.

If you have any intention of anything more than minimal track use, I would replace the entire axle assemblies, stub axles and transmission flanges with the later “Turbo” 108 mm version (928 P/N.) That gives you end caps, M10 CV bolts and the much stronger CVs.

BTW, does your ’84 have the OE “moon” plates between the CV covers and the Schnorr washers? How often do you re-torque the bolts? Do they move each time? What torque do you use? Do you know the precision and accuracy of your wrench?

Best,
Grady

[jpahemi]

Grady:
My CV's don't have either the half moons or Schnoor washers. I had them cleaned @ 50K miles and now with 90K I'm contemplating another cleaning. When the tranny was freshened up @ 65K I found the CV bolts loose after 60-100 miles; at first I thought the mech hadn't torqued them properly, but after reading these posts, it looks like it's common to tighten them up after fresh gaskets are used. About a year and half ago the synchro's were replaced and I didn't check the CV bolts after engine instalation. I'm heading over to the car today so I'm going to do a random check.
BTW, during the 90's I used to to DE the car quite regularly and the CV's have held up very well. The LSD was set to @ 80% lock, I wonder if this wears the CV's more; what do you think?
j.p.

[randywebb]

You need to use the half moons and esp. the Schnoor washers!

And yes do check the torque after a few whundred miles

[jpahemi]

Grady:
I got this M8 bolt kit from McMaster-Carr; it includes 25 M8 12.9 Metric Blue allen bolts (176,00 psi) and 100 M8 Schnorr washers. I'm surprised the CV's came from the factory without the moons and washers; I must have been very lucky they never came loose.
j.p.

[Grady Clay]

J.P.

Good for you.

Now, after you torque all the bolts to spec noting if or how much
they turn, remove one bolt. We want to inspect the condition of
the tin boot attachment where the head of the CV bolt sits. That
tin cover is very soft steel and probably the bolt heads have sunk
into it. This deforms the cover and leaves a raised lip around
where the head of the bolt sat – not good.

Measure the length of the bolt from under the head. (Measure a
new bolt and confirm it is 50 mm.)

Next find a suitable flat steel washer that is the same thickness
of the new or good used half moon washer plates that you are
going to use. This one measures 2.36 mm thickness.
IMAGE: CVWasherPlateM8a.jpg

Using the used bolt and a new Schnorr washer and the
temporary flat washer, torque the bolt in place and confirm
the threads come out the other side of the flange. MIL spec
(and DIN) is 1 ½ turns of thread. Less than one turn is too little
and more than two turns in too much but acceptable under some
circumstances.

If you use a too long bolt, you must pay attention to the end of
the bolt clearing the transmission casting on the inboard and the
trailing arm on the outboard. The real problem with too long bolt
is that many threads are exposed to the road environment and
can collect grime and sand. When you go to unscrew the bolt,
that grime and sand is dragged into the threaded flange and can
do damage to the threads.

When finding a suitable washer, pay attention to the OD. Too
large and it will ride up on the tin cover where it transitions from
flat to clear the CV balls.

Through this 1-bolt exercise you have determined how long your
new bolts need to be. It is a fair assumption that all four CVs
are the same but pay attention when you do the final assembly.

Put the used bolt back in for now (with new Schnorr washer) and
torque to spec.

In your picture, the bag of washers doesn’t have the Schnorr
logo. Are they the real thing or simply radial toothed conical
spring washers. Schnorr washers have the teeth set at an
angle to the radius and are sharp.

Here is a prior thread.

Schnorr homepage

Adolph Schnorr GmbH & Co. KG
Stuttgarter Strabe 37
D-71069 Sindelfingen (Maichingen)
Germany

Schnorr Corporation
4355 varsity Drive
Suite A
Ann Arbor, MI, USA 48108
Phone 734-677-2683
Fax 734-975-0408

Here is the link for the Schnorr washer technical data sheets (pdf).

Here is their contact:
sales@schnorr.com


OK … please report back what the tin cover looks like under the
head of the CV bolt. If too damaged, you will want to replace
them with new tin pieces when you clean the CVs and replace
the boots.

When you get some half moon washer plates, you will want to
check for proper clearance fit on the tin covers (as you did with
the single washer above.)

Best,
Grady

Oops To answer your LSD question – yes, it does add
some wear. It is probably about the same percentage as the
increase in rear tire wear from the LSD.

[jpahemi]

Grady:
I may have made a mistake in ordering the bolts. PET states the OEM units are 50 mm; now keep in mind my car came without the Schnorr washers and moon units; they may be to short if 50 mm is flush with the backside of the flanges, I'll need to check.
As for the washers, they're not Schnorr brand, rather Belville dual side conical serated washers (as per McMaster-Carr).
The teeth are pronounced but not sharp as you describe; should I get the real ones?
Looks like this car was a victim of the bean counters.
j.p.

From McMaster site:

Shape Belleville
For Screw Size 5/16"
Belleville Shape Serrated Top and Bottom
System of Measurement Inch
Inside Diameter Range .25" (1/4") to .349" (11/32")
Inside Diameter .25" (1/4") to .349" (11/32") .331"
Outside Diameter Range .4" (13/32") to .599" (19/32")
Outside Diameter .4" (13/32") to .599" (19/32") .512"
Minimum Thickness Range .02" (1/32") to .049" (3/64")
Minimum Thickness .02" (1/32") to .049" (13/64") .028"
Height .055"
Application Locking Washer
Specifications Met Not Rated

[Grady Clay]

J.P. said;

Grady:
I may have made a mistake in ordering the bolts. PET states the OEM units are 50 mm; now keep in mind my car came without the Schnorr washers and moon units; they may be to short if 50 mm is flush with the backside of the flanges, I'll need to check.

No big deal, you may just have some extra bolts. The important thing right now is to inspect the tin covers, find your existing bolt length and get the appropriate washer plates and other pieces.


J.P. said;

As for the washers, they're not Schnorr brand, rather Belville dual side conical serated washers (as per McMaster-Carr).
The teeth are pronounced but not sharp as you describe; should I get the real ones?

I’ll e-mail Schnorr here in the States and ask questions and get the sales pitch. Porsche has been using their product since about ’66 so they should be able to provide some insight.


J.P. said;

Looks like this car was a victim of the bean counters.

That seems to be the common perception. It would be interesting to have been a “fly on the wall” when they decided to only use 928 axles (108 mm CVs) and go back to using “half moon” washer plates and Schnorr safety washers.


I added this link to the pdf product specs in my above post.



Who on this Forum has the ability to measure the hardness of steel parts?
It would be very instructive to know the relative hardness of the surface under the CV bolt head, the Schnorr washer, the “half moon” washer plate, the tin CV cover, and the outer race of the CV.


Another issue that needs to be addressed is the compression of the gaskets (when used) and the compression of the sealant between the CV and the tin cover (when used). If those things must “settle in” to their compressed state before a final torque, we need to know that.

There is also the issue of the increasing layers of the “sandwich” that the bolts compress. On the latest version there is: The bolt, Schnorr washer, washer plate, tin cover, sealant, CV outer race, sealant, tin cover, and finally the threaded flange or stub axle. Some engine management and data acquisition systems use a tooth wheel under the CV bolt heads to sense axle (road wheel) angular speed.

With CVs that use a gasket, there is the issue of gasket edge parts getting between the steel clamping surfaces.


Let me repeat something that has been said many times. The CV bolts do not transmit the axle driving torque in shear or bending, they only provide the clamping force. It is the shear friction that transmits the driving torque and is from the high pressure provided by the CV bolt clamping force. This is the reason why it is so important to maintain the highest clamped pressure for the steel-to-steel surfaces.

Best,
Grady

[jpahemi]

Grady:
Here are some pics of the M8 washers. After looking at the Schnorr site; visually they seem identical. The flash reduces the black oxide finish. I have these in M10 and M12 in zinc finish, the width ratio seems reduced with the larger sixes.
j.p.

[Grady Clay]

J.P.


My recollection is that the Schnorr washers (lower) have a
pronounced and sharp “rake” to the serrations and that the
normal Belleview serrated washers (upper) have symmetrical
serrations. My perception is that a surgeon would want to be
careful handling a Schnorr washer with bare hands.

I’ll ask this question of Schnorr.

Best,
Grady

[jpahemi]

Grady:
I'll try to get the pics you requested of my CV's today. I'm very curious to see the condition under the bolts.
j.p
PS. I used a loupe to look at the serrations; they have clockwise pattern with the trailing edge having the bite. Not as pronounced as the lower image you show (Schnorr).
PSS. 'Just checked the M10 & 12 washers, those are quite dull.

[randywebb]

proposed edit:

"It is the shear friction [and on some versions, the projecting pins] that transmit[] the driving torque and [it is generated by] the high pressure provided by the CV bolt clamping force." [That is why the proper torque is ESSENTIAL.]

BTW - any testing lab - including those in engineering depts. at Ag. Univ.s will have the machines to determine hardness. I know there are some students on this bbs that could prob. wangle their way in...