IanM

I recently had my LSD rebuilt with Guard internals. Upon reassembly, I discovered that several of the 12 (6 each side) axle shaft to tranmission stub flange bolts did not seem willing / able to reach the specified 60 lb-ft of torque as per the service manual. Beyond about 45-50 lb-ft the bolts were turning too much for my comfort, so I gave up trying to reach 60. I figured that the bolts had yielded and were just stretching.

I've got a nice Proto torque wrench, and had it recalibrated not too long ago, so I'm fairly comfortable that it's working correctly. So I went ahead and bought 12 new bolts from Porsche. I tried installing the first one tonight, and the same thing happened, it seems to me that these bolts are starting to yield before my torque wrench reaches the specified 60 lb-ft. Am I missing something here? Have a got the torque spec wrong?

AudiOn19s

I did the same thing...actually rounded a copule of the bolts before I just backed down on the torque value. The OEM bolts are hex bit..the newer 997 bolts are star, neither seems to want to take the full 60 lbs without a fuss.

I think I ended up near 45-50ft lbs....thought maybe my torque wrench was off actually. I check them before ever event and haven't found one loose yet.

Andy

FFaust

I was at the shop a few days ago socializing, and a guy was installing the half-shafts on a cup. I heard him say the torque was 60 ft-lbs, so I know that that is the correct number.

Not sure why you are feeling what you are however.

JohnAnthony

this wouldn't be the first time a manufacturer listed too high a torque value for something

does anyone have
the grade
&
the sizes
for the bolts?

powdrhound

60 ftlb is WAY TOO MUCH!!

The maintenance manual states that the rear half shaft flange fastening M8 screws torque is 44 Nm (32,5 ftlb.) This is on a 996 GT2.

FFaust

Had to look it up: (haven't figured how to do a "print screen" on a Mac, sorry)

"Drive shaft to transmission, M10, 81Nm (60ftlb)"

GentlemanRacer

Right click anywhere above the location bar and you will see "customize toolbar" appear. Click on that and you will see a bunch of icons. There is printer icon. Drag it to any free space around your location/address space (I place mine to the right of the google search bar.

Voila! Now anytime you want to print page, just hit the print icon and the printer screen for your printer will come up.

Hope that helps

IanM

I just checked the bolts, they're M10 (10mm shaft diameter), and rechecking the service manual it definitely appears to spec these at 60 lb-ft.

JohnAnthony

need the grade now

8.8, 10.9, or 12.9

http://www.spirol.com/library/sub_ca...cations_us.pdf

http://www.cncexpo.com/MetricBoltTorque.aspx

http://www.imperialsupplies.com/pdf/...rqueCharts.pdf

GTgears

Are you using 900.067.123.02 or 900.067.229.01?
I ask because one is 48mm long and the other is 50mm long. This is a total shot in the dark but I wonder if you are using the 48mm one and it is just not quite long enough to get enough threads to get full strength.

IanM

The little baggies say 900 067 123 09, length is 50mm. Grade is 12.9. As per the www.cncexpo.com table provided by John, my bolts should use a torque spec of 47 lb-ft lubed and 62 lb-ft dry. I put blue locktite on the threads, so I wonder if they are acting as "lubed" and I should be using somewhere around the 47 lb-ft value? Thanks for those tables John - very interesting.

JohnAnthony

i would put them on dry if the torque spec is 60ftlbs
putting anything on the threads is lubricating them

GTgears

What John said. I have never put Loctite on a cv joint bolt. Stub axle flange and ring gear bolts, yes. Cvs, nope.

IanM

Thank you gentlemen.

Serge944

As mentioned above, torque to tension ratio is the most critical component of bolting. If the spec is for un-lubricated torque, you have to install without any lube. Otherwise, the friction doesn't account for as much of the specified torque, you end up putting too much tension into the fastener, and yielding it.

There is no fudge factor that you can apply...you'd have to run your own lubricated tests with one of these: