Recently got my car back on the road and have just over 300 miles on it. Mild SBC with 901 and Renegade CV shafts. Doing a hard pull in 2nd gear Friday and sounded like something exploded under the car - instantly lost all gears. Thought for sure I grenade the differential but it was actually where the outer CV joint bolts up to the drive flange. Destroyed both roll pins, and sheared 2 bolts. See pictures below.

What caused this and how to prevent it? Trying to take road trip with the wife in a week so want to get parts ordered asap. Too much torque? Maybe the bolts came loose? Other? If all my threads are good I plan to replace the roll pins and bolts and call it good. Maybe I'll add some thread sealant for insurance. Please advise.

Thanks,
Josh


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Likely the bolts backed off. Replace, locktite, and wired bolts should work out for you.

Thanks for the quick reply Andrew. Not sure if the bolts are recessed in the adapter or not. If I can get wired bolts in there I'll try to find some, and if not will locktite at a minimum.

914 Rubber has the drilled bolts and SS wire.

They are recessed into the adapter. Use red locktite on the adapter and blue on the bolts through the CV. That's what I've done. Also I use no gasket. I find the gasket could potentially cause the bolts to back out.


From your post it sounded like the bolts from the CV to the adapter backed out, caused the pins to sheer and the CV to come out.

If you keep having issues you could weld the adapter to the flange. Memory serves me that they are steel adapters.

agree with all of the above.
I will add that on the road trip, drive nicely.

Solid shear pins.
Bring extra bolts.

Thanks all. Cleaned the threads up so looks like no major damage. Was really sweating this one. Time to start ordering parts.

911 bolts are bigger than 914's

FWIW, I safety wire my inside CV bolts along with known good schnoor washers. I guess it could be done with the outboard ones by pulling the hub, lots of work....
On the other hand for a "permanent" fix you could install a 1.7

That output flange looks pretty bad. It must be replaced or at a minimum faced true. I have found that this is the biggest problem with the CV bolts coming loose. Once they have backed off, the area around the threaded holes gets pulled out a little. This creates 4 high spots where the CV mounts instead of the full face of the output flange. This prevents the CV from truly being tight against the output flange. This results in some movement causing the bolts to "walk" out.

In my Renegade CV shafts I replaced all of the stock roll pins with harden 10 mm stock.

The one time this happened to me 3 of the bolt backed out and there were no roll pins. New bolts and solid roll pins later no new problems. From then on I check axles before I use them as the PO obviously did it wrong.

In an effort to get this back on the road as soon as possible I decided to go with new bolts, schnoor/belville washers, stock roll pins, and locktite. I tried to find some 10 mm pins but gave up (probably a little early) when I didn’t find something easily.
I will also remove the passenger side for good measure and give it the same treatment. Thanks for the tip about confirming flatness, I’ll check for that also.

McMaster Carr has the stock in 10 mm. A bit of polishing to get sized and a few hours in freezer taps in easily. Lock tight one end.

get the 100mm cvs from the early 911 6 bolts no dowels and get sway away to make the axles. Was it your passenger side you blew out? I blew mine out with a 3.5 liter v6 engine upgraded to 100mm set up and have not had a problem. You do have to get the inner cv transmission side off a 911 they are getting harder to find.

Agree with above. Lose bolts, fix that and should be fine. I would not be opposed to welding the adapters on, either. That would be pretty quick and easy, actually. If you need another set of flanges, let me know as I have a bin of them.

I got everything put back together a couple nights ago. I removed the passenger side for good measure, and glad I did - inner bolts were already loose and flange was starting to back off I cleaned everything, used Schnoor washers all around and red/blue locktite so hoping that does the trick. I'll do the safety-wire upgrade as a future project.

Drove it to work ~35 miles today and all is well so far. We'll see if I make it home without the assistance of a flatbed this time