CV joints, Why they come off Options

[Bartlett 914]

I have experienced CV foints coming off my earlier car. This is an issue that many cars go through. I see threads on this topic from time to time. Most replies involve using new Schorr washers or wiring the bolt head. Some have used longer screws with jam nuts on the back side of the output flange. I do not see the actual cause being discussed and I would like to offer an explanation here.

What I have found is when the CV joint works loose. the stress on the bolts pulling on the output flange of the transmission distorts the flange. This results on a smaller contact surface between the CV and the flange. I corrected this using my lathe years ago an I have never had the work loose again. They worked loose in the past within a year.

Yesterday a local 914 member came over and we addressed his CV joint. One had come off. It did damage the the shift rod and caused considerable him grief. We replaced the shift console bushing and the shift rod. We then installed a replacement CV joint. I removed the output flange and put it in the lathe. Here are 3 shots. The first shows the condition before doing anything. You will see the flange surface is not clean. If it had been in full contact it would have looked better. The second shot shows a very slight clean up cut. Here you can see there is a 10 mm wide section where the flange cleaned up. Around all the bolt holes you can see a slight cleaning. What this means is no matter how tight you make the bolts that this is the only surface that will make contact! This results in allowing the CV to wiggle slightly under load. This leads to the screws backing out. So only a very small percentage of surface is making contact. For the correct results you need 100 percent contact between the two surfaces. The third shot is the final cleanup. I removed about .005" to get there. This metal is not real hard and cleans up easily..

If you do not have a lathe, then a flat surface and abrasive paper may work. Cutting a small countersink at each hole may also be helpful. You want to make certain that the threaded holes are hot high spots on the flange. New washers are advised.

[Porschef]

This is very interesting; years ago when I swapped out engines I put CV gaskets on where there hadn’t been ones. I too, had one loosen and detach from the flange (drivers side); fortunately I was going only about 25mph and started feeling the wobble. Minutes prior I had been going over 75...

My question is about removing the flanges from the tranny, I can’t remember how it’s done. If it’s simple enough I’d like to do this when I have the trailing arms out.

Also, are the gaskets mandatory? Been fine for years without them.

I do have a lathe.

Thanks in advance (IMG:style_emoticons/default/beerchug.gif)

[Bartlett 914]

This is very interesting; years ago when I swapped out engines I put CV gaskets on where there hadn’t been ones. I too, had one loosen and detach from the flange (drivers side); fortunately I was going only about 25mph and started feeling the wobble. Minutes prior I had been going over 75...

My question is about removing the flanges from the tranny, I can’t remember how it’s done. If it’s simple enough I’d like to do this when I have the trailing arms out.

Also, are the gaskets mandatory? Been fine for years without them.

I do have a lathe.

Thanks in advance (IMG:style_emoticons/default/beerchug.gif)

I should have mentioned about removing the output flange. There is a 19mm hex head screw that needs to be removed (drive flange expansion bolt). This is straight forward. Remove the bolt and pull out the flange. The oil should be drained first BTW. Installation is the reverse. Insert the flange fully but there is one caution that needs to be observed. When inserting the bolt, insert it slowly and do not push hard. Put it in slowly until it touches and slowly engage the threads. Tighten by hand until it seats without pushing it. The piece it threads into can be pressed out of position and this may cause you some grief. Torque 25 to 29 ft lbs.