sheared cv axle bolts help!

[harold12750]

LAST NIGHT HIGH REV SHIFT FROM FIRST TO SECOND GEAR AFTER WHICH I COULD PUT CAR IN ANY GEAR INCLUDING REVERSE AND IT ACTED LIKE IT WAS IN NEUTRAL . PUT CAR IN GEAR STEP ON GAS AND SPEEDO REGISTERS TOWED CAR HOME DRIVERS SIDE OUTBOARD BOLTS ALL SHEARED OFF ,INBOARD APPEARS INTACT I NEED TO PULL INBOARD JOINT TO SEE IF ANY DAMAGE THERE. MY QUESTION IS COULD THE SHEARED BOLTS OUTBOARD BE MY ONLY PROBLEM OR MUST THERE BE DAMAGE TO THE INBOARD JOINT OR DIFFERENTIAL ? CLUTCH SEEMS TO BE ACTING NORMALLY VERY MUCH APPRECIATE ANY IMPUT THANK YOU

[GothingNC]

Is your CAPS key stuck.

Your CV bolts may have loosened up a bit and backed out.

Same thing happened to me a few months ago.

I only had to pick up new bolts and used blue loctite, clean the boltholes oot with brake cleaner and used red paint to make index lines on the bolts to see if they have loosened.

I would pull the entire axle and replace all 12 bolts. It's was easier for me to bolt up the outer joint first.

I was lucky since it happened at low speeds.

[jdowty3]

I had the same thing happen but on the passenger side. With luck, you can use the sharp point of an awl to recessed ends of the bolts to turn out far enough to get a grip on them with needle-nose pliers. Then just clean the holes and replace the bolts with some new 12.0 grade cap head bolts.

[harold12750]

Thank you GothingNC , I fixed my cap locks .At first I thought you meant
something about the problem. I was going to ask what a cap lock was.Phew! So if I understand you correctly you had a similar experience where the outboard cv bolts sheared off, you replaced bolts and that fixed the problem ? Did you have the same symptoms ? put the car in any gear ( still rolling engine on feels like neutral no big noise like axle shaft banging around ,still seems to be intact on transmission end.

[Dirty Marty]

Harold,

Ditto on GothingNCs comments. The CV bolts are of an alloy designed to "stretch" a bid ove their life. It sounds like they were at the tale end of theirs or were reused when they should have been replaced. I made the mistake once with disasorous results at speed. Buy new ones, and loctite em as GothingNC suggests.

Dirty Marty
Fallbook,Ca.

[harold12750]

Thank you jdowty3 I will try that awl trick .I saw a show just the other day on hell mi. very small town must be nice!

[GothingNC]

I quickly shut down the car and placed it in nuetral when I heard a loud bang and rattle when I was shifting into 2nd.

I then coasted into a parking lot to park and stopped under a nice shady spot.

I now recheck mine every other weekend while I am cleaning the road dirt slime off the powder coated suspension.

I did not use the paper CV gaskets.Two local shops by me said they were not needed and sometimes they compress causing the bolts to loosen.
I have not seen a speck of grease come out so far.

Good luck !

[Grady Clay]

Here is the thread you should read. Yes it is long but very worthwhile.

Pelican rcecale, Randy’s classic thread.
”Reconstructing Constant Velocity (CV) Joints”

I would remove the stub axle from the suspension arm so you can inspect it carefully. You should lap the stub axle CV joint contact face with some fine wet ‘n dry paper laid on some plate glass. That surface must be flat. If not, check the CV joint’s surface also.

Reading the thread you will note the importance of new Schnorr washers, proper length bolts, plate washers and grease-free contact surfaces among other.

Best,
Grady

[Hugh R]

Ditto what Grady said about the other thread. Especially the right bolts, grease-free threads, use aerosol brake cleaner and q-tips to get the grease out, new bolts, new allen head socket, schnoor washers, and RETORQUE after 250, 500 miles and annually after that.

[harold12750]

Thank you grady and hugh I really appreciate your responses . I will read the thread indicated and will make sure everything is as it should be . When I took the sheared bolts out there where no washers of any
kind halfmoon or round . 83sc euro cab ,are there any called for or should I put them on anyway ? the other side had no washers either,
should I put some there to ? my next move is to order 12 new bolts
and a cv axle complete from our host and some loctite I guess. maybe more money but cleaner and much more straightforward.

[davidppp]

Hello there.

Typically fastener failure is attributable to undertorque at installation time.

In the case of these specific bolts, this can also be caused by the gasket slipping and preventing the metal to metal contact of flange and CVJ.

I know of no example of a fastener which is designed to stretch during service!

All screws work and hold their pressure principally through being adequately stretched during installation.

Any reduction of tension in the bolt during service, or inadeqaute tension at install.,will cause failure for sure..

A 10mm cap 12.2 head bolt needs plenty of torque!

Kind regards
david

[Gunter]

Do both sides, not just one.
Take the other axle off, clean, check CV's, regrease with Moly, new bolts with Schnorr washers.
I don't use gaskets, or the moon-schapped plates. Make sure that the new Allen bolts don't stick out too far; sometimes they need to be shortened by about 2 threads without the moon plate.
I pre-torque and final-torque criss-cross to 30 ft-lb on the 8mm Allen bolts. (6 mm Allen key)

[Groesbeck Hurricane]

One final question: are your moteur and transmission stock to your car or did you upgrade the engine and leave in an older transmission?

[randywebb]

- sounds like this was caused by the PO or his mechanic

Checking the CV joints ought to be added to the "Mandatory Things To Do When You Buy a Used 911" thread....

[Grady Clay]

Harold.

This constant velocity joint attachment failure is way too common. The root of the problem seems to be the bolts not being properly torqued (and re-torqued regularly), grease on the contact surfaces & bolt threads and the omission of Schnorr Safety Lock Washers and plate washers. The latter two were omitted by Porsche for a few years.

This is compounded by Porsche reducing the size of the CV joint from 108 mm to 100 mm in about ’76. By the time there were 3.0 and 3.2 engines the little 923 (912E) CV joint and M8 bolts weren’t up to the task with enough margin. Porsche rectified the issue by using the larger 108 mm (six M10 bolts) CV joint in ’86.

An issue you will need to contend with is bolt length. Adding the Schnorr Safety Lock Washers and the plate washers require longer bolts. There are CV boot retainers that are thin tin and thick aluminum; that complicate the issue. As you will see in the above linked thread, you must end up with the correct bolt length.

Why is it necessary to replace your axle assembly? Was it damaged when it came loose?

I recommend you do the same things to both sides. At least you should replace all the bolts. The general consensus is you should install Schnorr washers and plate washers if they weren’t originally fitted. See the thread for the reason for the plate washers. The Schnorr washers are “use-once” parts. It is advisable to keep a stash of these inexpensive parts.

As Hugh noted, re-torque all the bolts at 100-250 mi, 500 mi and annually thereafter. Spec for the M8 bolts is 33 ft-lbs (62 ft-lbs for the M10 bolts on the 108 mm CV joints.)

I realize that thread is long but it contains some really important information. The hour or two you spend studying it may save your 911 (and even possibly your life).

Just to clarify things; you have a 1983 911SC, European (RoW) specifications. It has 100 mm OD CV joints with six M8 bolts. (A M8 bolt takes a 6 mm hex Allen wrench.) This is an original '83 911SC and not a Turbo or M491 option.

Best,
Grady

[harold12750]

Grady, thanks again for your response,I think its great that people on this sight take a genuine interest in other peoples issues. In my earlier
years I was a mechanic and I seem to remember rebuiding some cv joints , I remember it being messy and somewhat time consuming,plus after the problem that I had,I thought in my case at least it would be easier to just replace the whole unit. I ordered the axle from our host and when I talked to the sales rep we concurred no listing for washers of any type were called for, I ordered 12 m8s . Are you saying I should put washers on even if not called for and if I do would the m8s that I ordered not be long enough ? Maybe I am reading more into this than is there. Please let me know. This was the result of a hard redline shift from first to second ,dont know what I was thinking anyway.Thanks again .Yes the car is a 1983sc euro cab .Also ,judging by the way the bolt remains were located, I dont believe they where loose just the weak link in the system to maybe protect other even more critical items,
differntial etc. I bought the car 3 years ago, It had 72k then and 95k now
I dont think it has the 491 option although it has the flared fenders and
turbo tail. sport model ?

i

[davidppp]

Hello, Harold.

The bolts must surely have been loose IMHO.

If correctly stretched, the bolt is loaded ONLY in tension...contarry to common belief I find..

Breakage could then occur with fatigue in tension...but there is negligible cyclical tensile stress in this application.

The role of the bolts is , or should be, solely to produce enough clampling pressure and thus friction between the cvj and flange..not to transmit any torque.

Kind regards
David

[jdowty3]

When I replaced mine, I can't say that I cleaned the holes as diligently as I could have per Gradys recommendation but mine have yet to loosen even a little since re-torqueing them after about 200 miles. The Schnoor washer and the 2nd re-torqueing really makes a difference in their longevity.

[harold12750]

I know you guys like to here end results, So here we go , the good ,the bad, and the ugly. As you recall the drivers side outboard cv axle sheared all 6 8/50mm bolts, I guess the retaining clip broke or whatever but the ball bearings where rolling everywhere, similar deal inboard , but all the bolts where still intact and tight but the joint just came apart when removed from the transmission . I removed 5 out of six bolt remains sucessfully but could not get the last one out . I tried to drill it but the bolt was to hard and the bit to soft. I was able to drill about half of the bolt ,but couldnt get it out . Soon I know I will have to remove the axle nut, tap out the stub axle, have the hole welded and have it rethreaded, I assume this can be done . If not, I will have to replace it. But in the mean time I wanted to make sure I didnt have any other problems so I ordered a complete axle asembly and 12 8/50mm bolts. In 1983 porsche I guess deleted any plates or washers, and the pelican rep concurred. When I went to install the new axle shaft the outboard bolts were bottoming out preventing the wheel from turning!I called pelican back and they listed no plates for 8mm bolts and the snorr washers were back ordered from porsche. I know you guys especially the purists will think I am crazy, but I really want to be driving my car .
The broken bolts all sheared off at approximately the right length for the new axle. I guess the replacement axle has a thinner flange or something to make the 50mm bolts too long without washers and plates .So I completed assembly with 5 out of six sheared bolts and took her out for a very tentative test ride. To my amazement the car purred along with no issues! As a matter of fact there is a noticeable improvement in shifting since the repair. I am guessing that the bolts were working loose over a long period of time,not checked for 20+k miles , possibly affecting shifting. I know I have to repair it correctly with washers and plates and hole repair , but at least I can still drive it.I guess I missed the thread on tightening and frequent checking of cv axle bolts .Please all you 911 guys check your cv bolts for safety and who knows , maybe your car will shift better to ! I welcome all responses

[jdowty3]

I think the newer axles that come with the CV have a thinner CV flange and several people have had the same issue. Originally the CV bolts were 48mm so I'm not suprised that the 50mm would bottom out with the thin flange. If 40 or 45mm will work then check with McMasterCarr or MultiMetric and get new 12.9 grade bolts. The old bolts have already been stretched and stressed and really should be replaced.