Sanity check on rear half shaft bolt torque
10-03-2018, 10:57 PM
#1
Three Wheelin'
Thread Starter
Sanity check on rear half shaft bolt torque
ive just replaced the automatic transmission mounts and have reconnected the two rear half shafts.
Thd WSM as I read it gives 61 ft-lbs for the hex bolts that secure the half shafts to the transmission. Am I reading that torque correctly? Seems pretty high.
thanks
Thd WSM as I read it gives 61 ft-lbs for the hex bolts that secure the half shafts to the transmission. Am I reading that torque correctly? Seems pretty high.
thanks
10-03-2018, 11:12 PM
#2
Archive Gatekeeper
Rennlist Member
Rennlist Member
I prefer 66.
10-04-2018, 09:06 AM
#3
Rennlist Member
What's the thought on using 66?
10-04-2018, 09:57 AM
#4
Rennlist Member
Most fasteners are designed to be stressed to about 70% of yield to give a reasonable factor of safety so over torquing a bolt by 10% generally speaking is neither here nor there. On the other hand does anyone really think that Porsche did not know what they were doing when they specified a torque for a specific bolt or did not amend the WSM specs if they found they were too little?
When I challenged Porsche over the problem with the flexplate clamp slipping issue 20 years ago they told there was no problem with the system- when we demonstrated that there was a problem within half an hour they came back to the local agents whio I had been prodding with the now famous [infamous?] "fix" to use a new bolt and over torque by 10%- and that did eff all! I was then trying to develop a solution with some of my professional colleagues when I found this list upon introduction of the internet to Oman in the public domain and lo and behold Earl Gillstrom suggested the Loctite solution- I think my S4 was the second vehicle in the world to have this applied a couple of days later and problem solved and still being applied on my current 928. With hindsight maybe we could have tightened it even more by taking that bolt to 90% of yield [which it would have sustained] and maybe that might have worked but the stock item did not on my car at least [and many others that have had their engines wrecked].
Bottom line if the system works and applies the necessary clamping force why would one feel a need to add more? A technocrat [fool?] can tell you if you add twice as much concrete to the house foundation it will take twice the load- an engineer will tell you how much is needed and no more!
When I challenged Porsche over the problem with the flexplate clamp slipping issue 20 years ago they told there was no problem with the system- when we demonstrated that there was a problem within half an hour they came back to the local agents whio I had been prodding with the now famous [infamous?] "fix" to use a new bolt and over torque by 10%- and that did eff all! I was then trying to develop a solution with some of my professional colleagues when I found this list upon introduction of the internet to Oman in the public domain and lo and behold Earl Gillstrom suggested the Loctite solution- I think my S4 was the second vehicle in the world to have this applied a couple of days later and problem solved and still being applied on my current 928. With hindsight maybe we could have tightened it even more by taking that bolt to 90% of yield [which it would have sustained] and maybe that might have worked but the stock item did not on my car at least [and many others that have had their engines wrecked].
Bottom line if the system works and applies the necessary clamping force why would one feel a need to add more? A technocrat [fool?] can tell you if you add twice as much concrete to the house foundation it will take twice the load- an engineer will tell you how much is needed and no more!
10-04-2018, 11:00 AM
#5
Rennlist Member
Make sure the threads are clean of all grease(not just the bolts) a dab of Blue Loctite won't hurt, torque to 66ft lbs like Rob E. said, then check em after 100 miles or so.
Never had one come loose, even with 928's putting down 500+ RWHP
Also the same w/ the TT clamp bolts, 66ft lbs.
Dave K
Never had one come loose, even with 928's putting down 500+ RWHP
Also the same w/ the TT clamp bolts, 66ft lbs.
Dave K