Siliconing a CV Joint??? Newbie Question
I'm reassembling my CV jiont and axles for the ZInk Z-10 project and noticed that it was siliconed on disassembly.
I used standard auto parts store CV joint grease and was wondering if I need to or should reseal with joint to the brake rotor and boot ot just let it go.
I hate leaks of any kind on a race car, but it is overkill?
Thoughts?
Thanks
Keith Lawrence
Pittsburgh PA
1978 Zink Z-10c
1964 AD FV Mk I
Seal it! And seal the back side of the rotor against the trans flange as well. CVs with inboard brakes run hot, many times liquifying the CV grease. The last thing you want is for the grease to lube the brakes.
Just the advice I was looking for.
Thanks
Keith
Last edited by Keith Lawrence; 03.03.09 at 1:58 PM.
I can't believe I'm disagreeing with Richard...
My experience is that putting silicone seal on the mating surfaces of the CV joints to the hubs results in loose fasteners, the sealant lubricates the surface so that the joint slips and the fasteners stretch and loosen. The torque is supposed to be transferred by the friction between the two dry steel surfaces clamped by the bolts, not by shear on the bolts themselves. Since I started cleaning the surfaces with brake clean prior to assembly, I solved the bolt loosening problem and haven't really had a goop escaping problem either.
My $.02 anyway.
Brian
I think it is possible to "seal" the joint without contaminating the mating surfaces. As far as the mating surfaces, I agree with Brian (there was a diatribe by SJ several years ago on the S2 board regarding this very situation). After the units are bolted together a small bead of silicone can be smeared around the parting line of the CV/flange. Not sure how this would be done between disc and flange.
Charlie Warner
fatto gatto racing
'Cause there's bugger-all down here on earth!
Brian:
The "secret" is in where you put the silicone. Every CV has a chamfer on the OD edges - this is where the silicone goes. For the rotor to flange seal, just a tiny bead at the OD edge of the flange is usually sufficient. In 30+ years of doing this, I've never seen a CV loosen up when the silicone is applied correctly.
If you have a lathe handy, one thing you can do is machine a shallow groove in the CV mating faces, and put the silicone there.
Silcone applied to the two surfaces acts like a lubricant to a small degree. I agree with the idea of putting some silicone on the joint after assembly, around the exterior.
Jim Gustafson
Then we're both right. We both don't put silicone on the mating surfaces, which to me is the key. Putting some around the outside edge may well help keep goop inside, and I do like the idea of putting a groove in, though if I did it I would probably make it an O-ring groove or something like that.
I've seen people do it, I've done it myself, but I confess I never actually thought that putting silicone seal on the outside of a joint made any difference. For me, it has to be sandwiched and seal between two surfaces to actually do anything. If you guys really think that putting it around the outside of the joint makes a difference, maybe I'll try it.
Brian
Brian,
I would think if the CV joints are installed properly (I.e. with proper washers, which is where the vast majority of people go wrong - causing loosening CV joints and leakage of heated grease) the sealing should be such that no leakage (or loosening) will occur.
Charlie Warner
fatto gatto racing
'Cause there's bugger-all down here on earth!
For a lightened CV, would you then also suggest applying silicone around the mounting bolt holes as they are inside the OD seal and the grease could bypass the seal? Or does this not happen in practice?
Just wondering as this wouldn't be an issue for the non-lightened version which may be what is being used considering this is a vintage/historic thread.
Thanks for the idea.
Jonathan
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CV joint washers?
I don't use washers on CV joints, I use those hardened load-spreaders that look like stock VW pieces that have two holes in them. Are those the right things to use?
Brian
It absolutely happens. I missed a small area around a hole in a lightened tripod, and spun out a sizable amount of the grease.Originally Posted by Jonathan Hirst
Red Permatex
I have also solved this by trial and error. I once used silicone on the surfaces to stop CV grease migration on in-board rear brakes.
I now use the red high heat silicone on the outside at the seam between the flange-cv and rotor-cv - small bead that I smooth out gently with my finger. Works great - no signs of grease.
Brian,
I imagine those thingies are fine, unless non-hardened washers are used under the bolt head. The magical word here is "hardened." And I don't mean AN washers. They are not hard. Hardened washers are required. Otherwise the washers eventually give under torque and the CVs loosen. This is one reason to put the bolts in from the outer to the inner. I know it's a pain to put the washers and nuts on that way. An alternative is to make sure hardened washers are installed under the bolt head before the flange is installed in the side plate. Hardened washers are not unavailable or expensive. Also, use the proper boot. There are several bolt circle sizes out there. One size is "ever so close" to the proper size and a bit of filing makes it "clearance to locality."
Charlie Warner
fatto gatto racing
'Cause there's bugger-all down here on earth!
Humm, this is interesting. I've never sealed the CV's on my RF78, and haven't had any problems using Red Line CV2 grease. I see a few "trails" from the joint, but not enough to cause any brake problems.
Steve
One thing to help retain the integrity of the grease is to use Red Line.
Greater hi temp stability and the only thing I use for CV joints.
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