Axel fell off

[squerly]

I have a 1988 930 and Friday the axel came loose from where it connects to the transmission. It is held on by 6 allen head bolts. So under the car I go to reconnect it. I have been told that I need to torque these bolts to 65 lbs. So I did, or I thought I was anyway but I found out that my torque wrench was lying to me and I have over torqued the bolts. Do I need to loosen them up and then re-torque them to 65 lbs or do you guys think that they will be ok as they are? I don't know what damage can come from exceeding the recamended torque settings.l

[gorfllub]

I dont know your answer, but did it give you any warning or sounds before it fell off? Mine clunks on occasion, but I have currently decided its a CV joint going bad. I am not too interested in having the axle fall off mind you.....

[84toy]

Torque wrench is not lying, that's way too much torque for those bolts. You have most likely stripped the threads and the unit will probably have to be replaced or repaired.

[squerly]

I'm not sure I was clear so let me start over. I know why the axel came off. I had some suspension work done and when they bolted the axels back up, there was some miscommunication and they didnt' get torqued. When it came off I was in my driveway and there was no drama. It just went "clunk" and that was that. I was bairly moving. The bolts were not stripped and I just put the axel back in place, tightened up the bolts and then torqued them. I am sure that I over torqued the bolts though. Not sure by how much. Car runs fine but I just dont want any unexpected problems by the torque being wrong.

[rcwaldo]

More than likely those bolts are now stretched. Best to replace all 6. No problems!

[Craig 930 RS]

S/B around 30 lbs I believe.......

[ausdilecce]

You can go and get those bolts from a store that sells bolts.. Bring one of the old ones with you ( the bolts are stamped with a rating ). You should be able to get new bolts for about USD$3-6 a bolt.

I might have been lied to but I have been told that these bolts are a 'one time use only' bolt.

Good luck

[squerly]

Originally posted by Craig911
S/B around 30 lbs I believe.......

After 67 they used used a larger bolt and is torqued at 60 lbs. I'm sure that I torqued much higher than this although I'm not sure how much higher.

[Tyson Schmidt]

Originally posted by Craig911
S/B around 30 lbs I believe.......

Depends on the bolts. Early 4-bolts were 61#. later SC style 6-bolt were 30#. Later Carrera and I think 930 were 61#.

[Wil Ferch]

I believe Tyson is closest to the truth but not completely either....

The 930's and G50's use a 10 mm x1.5 bolt torqued to 61 ft-lbs. This is correct.

The 915's use a 8 mm x 1.25 bolt torqued to 30-32 ft-lbs...

Tyson...maybe you're thinking of the 100mm vs 108mm axle flange diameters that were a running change around Model Year 1985, for 915 equipped cars ??

Wil

[Craig 930 RS]

** When installing a CV and a NEW gasket, make sure to retorque. **
They become quite loose with new gaskets!

[BeauBlues]

You can go and get those bolts from a store that sells bolts.. Bring one of the old ones with you ( the bolts are stamped with a rating ). You should be able to get new bolts for about USD$3-6 a bolt.

I actually went to a local hardware store and picked up the exact same bolts for like 50 cents each. I found them in the metric section.

[Grady Clay]

First things first: Have your torque wrench properly repaired
and calibrated.

PET6 shows your ’88 911 Turbo Carrera having “Drive Shaft”
axle – CV assembly 930.332.037.04 that uses an end cap at
each end of the axle. This axle uses 12 M10x50 12.9 internal
hex bolts (900.067.123.01) on each side of the car. It also
shows the “moon” plates (911.332.191.00) under the bolt
heads. It does not show the M10 Schnorr lock washers
(999.523.100.01).

Inspect the threaded flanges for damage when the CV came off.

I would recommend replacing all the CV bolts and adding the M10
Schnorr lock washers (available from our host) while keeping
the “moon” plates in place. Care should be taken to insure the
bolts protrude through the transmission flange and stub axle
flange by at least one thread but not more than two (1 ½ is
ideal.) The bolt threads and flange threads must be clean and
free of grease.

When you tighten the bolts go to about half torque spec on all
them. The final tightening should be in one continuous motion
with your newly calibrated torque wrench.

Re-torque after a week or so of driving. Check more often than
annually, particularly if you track your car.

There has been much posted on this subject – use the search function.



Here are the 911 Carrera axle (friction welded stub axle) and the
911 Turbo Carrera axle with the bolt-together at the stub axle.

IMAGE: 930AxleWithEndCap01
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

Porsche says “NOTE: Since the new CV joints have a sheet metal
housing, washers [moon plates] 911.332.191.00 must be used
when installing.” It says nothing about bolt length or Schnorr
lock washers.


Here are the transmission axle flanges.

IMAGE: 930AxleFlangeWithEndCap03
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

You cannot use the 930 axle with the end cap with the earlier
transmission axle flange or stub axle flange because there isn’t
enough surface to tighten against. As I recall, the end cap also
doesn’t fit in the earlier flange recess.

Here is the exploded view of these parts:

IMAGE: 930AxleFlangeWithEndCap02

"
"
(C) Dr. Ing. h.c. F. Porsche A.G.



Here it is with the M10 Schnorr lock washer.

IMAGE: 911AxleWithoutEndCap01
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

Best,
Grady

[squerly]

Good lord Grady, I don't know what to say. Thanks for sharing your wisdom. Should I expect a bill to show up in the mail????

[Grady Clay]

No bill.

My intent is to simulate critical review of what Porsche has built and written. These excerpts are to foster that.

So many enthusiasts are swapping parts around, it is very important to have correct information available. Some of the Factory information is incorrect or has been up-dated. The ability of the Forums to review the information is possibly life-saving.

Had you been under full power and in a right turn on a non-divided highway, the outcome could have been far worse than a few expendable bolts. Neither the 930 nor your bod take kindly to a high speed head-on with a semi-trailer.


Something I didn’t include is the torque specs for the M10 grade 12.9 CV bolts. According to the Factory Workshop Manual for the Turbo Carrera (WKD 481 321) the “Rear Axle Torque Specifications” are 83 Nm (60 ft-lbs.) Is this correct? This page 42-03 is dated 3/81. Thank you Chris Bennet for the manual.

Best,
Grady

[Grady Clay]

STOP –
STOP

- WRONG TORQUE SPEC IN BENTLEY.
WRONG TORQUE SPEC IN BENTLEY

I just looked at a Bentley spec book that listed the M10 CV bolt
torque at 33 ft–lbs WRONG. It should be 60 ft-lbs. Everywhere
I look confirms 60 ft-lbs.

If you torqued your M10 12.9 CV bolts to 33 ft-lbs re-torque
to 60 ft-lbs before you drive again.


This is true for every 911 with M10 12.9 CV bolts.

I haven’t checked but I’ll speculate the M8 bolts are
torqued to 33 ft-lbs. Perhaps this is why there is a rash of loose
CV bolts – there is an error in Bentley.

Best,
Grady

[Jim Sims]

36 ft-lbs for the class 12.9 M8
60 ft-lbs for the class 12.9 M10

A 12.9 M8 screw will fail (combined torsional and tensile stress) somewhere around 50 to 55 ft-lbs depending upon thread friction - lubricant, plating on screw, etc.

There is lot's of confusion in the repair books (including 101 projects) compounded by the way Porsche changed the sizes of the CV joint screws over the years.

Defective CV bolt or is it me?

[Sumotang]

Does this mean if I have a 915 gearbox and the 6mm hex nut I should torque to 36 ft.lbs?

[Craig 930 RS]

A G50/50:

What torque?

[Jim Sims]

Screw (bolt sizes) are according to the outer most thread diameter of the male thread. The wrenching feature size (inside hex, outside hex, triple square or whatever) is not the screw size. An 8mm socket head cap screw (one of the size/types used on 911 CV joints) will be 8mm in diameter across the threads and will usually have a 6 mm inside hex wrenching feature in the head (although there are some inside triple square screw heads in CV joints but they are more rare). These 8 mm, strength class 12.9 screws should be tightened to 36 ft-lbs in this CV joint application. Jim