CV Boot bolts backed off Loose ! 78 SC

[scotricker]

Well, oops.

I was under there for a completely different task, and noticed the CV Boot bolts were loose. One backed off a bunch. The others not so tight either. All 4 boots.
Hint, grease splattered around , thought I would check. I replaced the boots a while ago, but not too many miles since.

Now all happily tightned up again, but did I miss something? Was I to use new bolts? Or lock washers? Or lock tite on the ends. Or clean the grease off. Or blame the last guy? (me) Or all of the above?

No disaster, but it surely it could have been.

[Trackrash]

Yea, seems to be a problem with SCs.

I wonder if anyone uses Loc-tite?

[Superman]

I am no expert on the various types of CV fasteners but I know they function reliably if installed to spec. Your bolts are likely 8mm. They may or may not require the 'crescent moon' spacer thingies. They likely do require brand new Schorr washers, and this is what gets some folks into trouble. Also, as with any rotating part with fasteners on their periphery (such as lug nuts, brake rotor bolts, etc.), it is very important the fasteners are torqued very evenly. All torqued exactly the same.

[Trackrash]

Adding to what superman said, it has been suggested to check or re-torque after a few miles.

[Larmo63]

Drilled head bolts are available to use with safety wires.

[scotricker]

Schorr washers ? sounds like a good idea, what are they ? got a part number ?

[Ian Comerford]

Try this for info https://www.schnorr-group.com/en/products/safety-washers/

[Ian Comerford]

Originally Posted by Superman

I am no expert on the various types of CV fasteners but I know they function reliably if installed to spec. Your bolts are likely 8mm. They may or may not require the 'crescent moon' spacer thingies. They likely do require brand new Schorr washers, and this is what gets some folks into trouble. Also, as with any rotating part with fasteners on their periphery (such as lug nuts, brake rotor bolts, etc.), it is very important the fasteners are torqued very evenly. All torqued exactly the same.

Agree with all of this. I think you will find you need the crescent moon spacer thingies if the metal part of your boots are the thin steel type. The crescent helps apply a pressure over an area without distorting the steel. The older/original type had thick steel which only needs the Schnorrs.

[timmy2]

My 78 had/has no special washers originally and still do not. They haven’t moved in 10,000 miles.
Install the bolts clean and dry and torque properly with a calibrated torque wrench.

[RWebb]

safety wires are not effective in this application - the engine torque will quickly shear CV bolts if a few of them loosen

I'd also bet on re-use of the Schnorr washers as the culprit - the female & male threads also need to be bare of all grease & oil - use Q-tips & brake cleaner

[ClickClickBoom]

This comes up with alarming regularity, look up CV reconstruction. A lot above is inaccurate.

[Larmo63]

[HarryD]

Recently happened to me as well. My Story: CV Bolts!

All seems ok. Will retorque after my DE Day and AX later this week.

[DanielDudley]

Originally Posted by timmy2

My 78 had/has no special washers originally and still do not. They haven’t moved in 10,000 miles.
Install the bolts clean and dry and torque properly with a calibrated torque wrench.

This ^^^^
People are squeamish about putting the torque to them, or use a tool that can't get there and guess. These bolts are so stiff that they need that torque to keep tight. They just have to loosen a little bit and they are loose, because there is no stretch to speak of.

[T77911S]

one thing that I think happens is bolts can get replaced over the years and are too short.

make sure 2-3 threads stick out past the flange.
you can order the bolts in 5mm lengths.

I got mine along with new schnor washers from Fastenal in bags of 50 but someone posted this site which looks to have good prices on the bolts also.

as best you can, clean and dry....its not easy.

https://www.belmetric.com/

[piscator]

+1 Belmetric. Matt and his crew offer great service.

How 'bout Nordlock washers?

https://www.belmetric.com/nordlock-washers-c-4_1547/

Just thinking out load, but has anyone tried using bolts long enough to put a Nylock nut on the other side of the coupling? Would there be enough room? I'll have to look

[lespaul]

I use Stage 8 on my CV joints for my '78SC. They have never failed or budged.

https://www.stage8.com/cv-joint-locking-bolt-kits/

[theiceman]

there is a lot going on in this thread.. my 78 had no crescent moon washers .. nor schnorr washers .. they were just put on correctly from the factory .. adding these things are never bad. but keep in mind you are effectively shortening the bolt if you add these. you must compensate for this with your replacement bolt.

The vast majority of these back out after engine removal work or after CV work. this is because grease gets on the threads. Like most things a solid standard work will resolve these issues.

firstly always replace with new bolts. but do not put them on right away. put your CVs on and in place with your old bolts and schnorr washers and crescent moons and whatever you like..
then ONE AT A TIME .. remove a bolt.. clean the threads with brake clean and a test tube cleaner.. replaceable the bolt with a brand new one and tighten .. move to the next bolt and repeat.

after you have accomplished all bolts, torque to final spec in correct pattern.

recheck in 500 miles
recheck in 1000 mile


done.. you do not need loctite

like most things done correctly , you have to be methodical and patient.

[mikedsilva]

I see that the greasy threads can cause an issue and notice that on my 964, the CVs were covered with a metal plate before mounting to the box output flange.

Can these metal covers be used on the older 911 too?

[pmax]

If you didn't use this or equivalent during the install, that's the problem



More info in the 100 page CV thread.