CV Shafts

[landyman96]

Hello Pelican,

I have a 66/67 Porsche 912. I am trying to diagnose a rumble noise at 50+ MPH. I believe it might be coming from a bad CV shaft. The CV shaft I removed is definitley bad, it has a hard spot. Not 100% thats my noise though. Regardless, I need to replace it. Will a newer CV joint/CV joint rebuild kit fit my car? I am looking at them and they look the same. I cant find a rebuild kit for an SWB car.

[Trackrash]

Post a picture of what you have. Good chance it has been upgraded at some point.

[landyman96]

Both sides seem to be 6 bolts.

Will this CV rebuilt kit work on this?

93033203400

[cmcfaul]

I would replace the whole thing (shaft with cv's). It's a messy job replacing the CV's and boots. If one is bad the others are close behind. Those look like they have lived a good life.

Chris

[Trackrash]

Here is what I know. Are you replacing just the boots or the CV joints?

[Walt Fricke]

1) - disassemble your existing CV/axle system.
2) - disassemble and clean both CVs
3) - inspect each CV. You are looking for pits or distortions of the balls (not likely), grooves you can feel with your finger in the inner or outer ball grooves (shiny spots are normal, grooves mean the heat treat is starting to go or otherwise there is enough wear to cause noise), or broken ball cages. If the wear grooves aren't too deep and are off center axially, you can reverse the CV so the wear is on another part of the groove.
4) - If a CV is bad, replace it. You say you can feel a "hard" spot on one CV - I'd start the inspection process with that one. You could just disassemble that one, but since you have them all off, cleaning, checking, and regreasing all four seems like it would give peace of mind.
5) - Some of your boots look good in the photos - if they aren't torn or cracked, I'd reuse. One looks like it is torn off the CV?. You can purchase boots, but be careful - some boots have a thin flange, some a thick flange. Both work, but thick flange boot holders require longer bolts, so be sure your bolts stick their threaded ends out as far as before, but no farther if you end up with a different style boot flange.
6) - if it were me, I'd reuse the bolts and washers. Just be sure you get things properly torqued on reassembly in the car, and retorque after some highway miles/hours just to be sure. However, you will find lots of advice saying you need new bolts and Schnorr washers. Nothing wrong with that other than extra cost.
7) - you might take a wire wheel or other abrasive to the outside surface of those CVs so they don't look so groody on reassembly, though that won't improve their performance.

8) - The helpful picture of these various parts doesn't show the diameter for the 65-68 CVs. If it is 100mm, you can use the other 100 mm 6 bolt CV, which is readily available. If the early one is thicker or thinner, perhaps all that is needed there is different length bolts? Too short is an obvious issue, but if too long the ends of the bolts hit things. Easy enough to avoid.

9) - Even with the one presumptively "bad" CV, my experience is that this is more apt to show up as noise at slow rather than high (as in 50 mph) speeds. Another wear and noise creating item is the rear wheel bearing. If yours are original to the car, they are a likely suspect. If just one side is going bad, you can sometimes diagnose that by weaving the car sharply on the road. The more loaded side will produce more noise than the other if the bearing is starting to go.

10) - For clarity, don't confuse the axle with the CV. Both are components, but the axles themselves are, luckily, nearly immortal.