Christopher Zach

Interesting one. While driving down Rt. 1 I heard a loud noise from the rear of the car, figured it was a flat so pulled over on side road.

Nope, turns out the driver's inner CV joint bolts had all come loose and cv shaft dropped. Glad I was not going 100, but is this normal?

More interesting, I noticed a few months ago that several bolts were loose so I tightened them all up. Do they need insane torque or lock tite on them?

Hopefully the outer CV joint wasn't trashed. Waiting now for Mr. Tow Truck.

C

polecat702

There's a torque spec, in the WSM. That's what I went by when I swapped out transmissions in my 89. I may have used some blue Loctite, too. I've had no problems since.

Speedtoys

proper torque need no loctite.

Unless you like drilling out stripped bolt heads next time in.

dr bob

Chris --

Certainly not "normal" but it happens. There's probably little comfort in knowing that you aren't the first 928 owner to experience this. I remember one owner explaining how the just-acquired car had gone through a slew of post-delivery maintenance including new CV boots and service at a normally-reliable Porsche shop. Then the grinding and banging noise when the bolts fell out a very short time later.

Torque on those is an impressive 60 lbs/ft tight per Rob Edwards' bolt torque table. This assumes clean bolts and threads in the drive flanges on the differential.

The easiest way to get a torque wrench on them is at the end of enough extensions to reach out into the wheelwell area. Use a good impact-rated hex driver, and make sure the driver is fully engaged in the bolt head. There are washer plates that sit under pairs of the bolts; be sure to get some to replace those lost from yours when you order the replacement bolts.

GlenL

This is not uncommon.

It is avoided by having clean threads and not getting grease on them when installing it. I use Blue loctite as it resists vibrations and backing out while being easily removable.

Christopher Zach

Sounds good, I didn't want to over-torque the bolts and risk a strip, but I'll pull them all, clean, torque, and just check on a monthly basis as a part of the "walk around". Worse things happen :-)

Car is back at the house safe and sound, glad I had the towing hook and roadside assistance....

Rob Edwards

This is one way to get to them for removal. Not sure how comfortable I'd be using 32 inches of extensions for the final torquing.

gazfish

Is there some magic trick to getting the bolts through the CV joint without picking up grease. I've repacked one side and installed a new shaft on the other and can't see how you can push the bolts through and have access to the threads on the other side to clean them?

Imo000

I tighten them to "good'n tight". Probably more than the spec but never had a problem with them.

AO

ORLY!?

Why would that be?

GlenL

This is the source of the problem. The grease gets everywhere and the greased bolts go into greased holes with grease under the heads. The vibrations loosen them, easily.

The "trick" is to have everything clean and the grease controlled. Clean that faces and holes on the CV joint. Clean the stub shafts. Clean out the threaded holes. For those, I'll blow them out, clean them with brake cleaner, blow that out, run a thread cleaner into each hole, and then finish with more brake cleaner and air.

The "Thread cleaner" is a bolt that has grooves sliced into it with a file. That goes into the hole after a dip in laquer thinner and gets cleaned after each use.

Multiply by 6 by 4 and that's a lot of work to get clean bolts into clean holes. So... People don't do it and, later, they come loose.

Rob Edwards

If you're asking whether there's any difference in the torque achieved with 3 feet of extensions vs. no extensions, no, there isn't. I wrote that in a moment of temporary physics insanity, please disregard.

hacker-pschorr

https://rennlist.com/forums/924-931-...-cv-bolts.html

dr bob

That's Rob's former GT at a clinic at our former Glendale bungalow. Rob has the camera and the big end of the stacked extensions, That's yours truly on my back steering the hex bit from bolt to bolt at the drive flange end. Substitute the torque wrench for the ratchet on installation.

The later inner joints have a steel cover on the end to keep the grease inside, and protect the otherwise-exposed end of the half-shaft where it pokes through the inner CV joint. There's a gasket fitted inside that cover. I use assembly wire or a few small plastic cable ties through half of the holes to keep the grease inside during bolt-up. By the time I'm ready to put the axle assembly in, it's pretty much white-gloves clean. As others mention, the threads in the drive flanges are cleaned as are the bolts and washer plates half the bolts go in snug but not tight. Then the ties get cut and pulled ot to make room for the last bolts. All are drawn up evenly snug, then tightened in a patter similar to what you'd use for wheel nuts. That way everything stays clean.

I haven't personally felt the need to add any threadlocker to the bolts. With the tension put on them with the required torque, clean threads, they aren't going to wander out on their own. Do it if you feel the need, but remember that you'll need one of GlenL's thread chaser/cleaners every time you move a bolt. To get the old threadlocker out before reassembling.


My two cents.

GregBBRD

Lazy mechanics are the ONLY reason for these bolts coming loose, on a street car.
The amount of grease on the bolt makes zero difference, unless you are using Krytox grease (and there's a zero chance that anyone with a 928 street car is using Krytox.)
If they are torqued to 62 ft.lbs, with an accurate torque wrench, they will never come loose.