| So about that LH drive shaft.. [message #359883] |
Fri, 30 October 2020 12:15  |
Silvernort
Messages: 95
Registered: June 2019
Location: Rock Springs, WI
Karma: 0
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Last week my LH drive shaft came undone from the inner drive hub. Turned out to be easier to fix than I worried it would be. I had to remove the drive hub to chase the threads as I couldn't get a clean start on some of the holes. A look at the repair manual said "remove L.H. drive axle." Yikes! But no, it swings up high enough to pull the hub (drive shaft) out after undoing the 9/16" bolt. Whew! That's a big difference. Maybe they meant just to unbolt the inner CV from the hub, of course the GMC did that for me. Thanks alot.
After cleaning well and chasing the holes from the back side, I applied my favorite spline lube and put it all back together: 45 ft/lbs on the 9/16" shaft bolt and 65 ft/lbs and Locktite blue on the hub bolts. Didn't see any other damage other than a small dent in the tranny dip stick tube, so should be good to go.
Cheers
Shane Harvey
1973 26' "Packer Backer", 1976 Palm Beach, 1965 Dart
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| Re: So about that LH drive shaft.. [message #359887 is a reply to message #359883] |
Fri, 30 October 2020 14:10  |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Sir, the outer CV end nut is 140-280 ft lb.
Silvernort wrote on Fri, 30 October 2020 13:15Last week my LH drive shaft came undone from the inner drive hub. Turned out to be easier to fix than I worried it would be. I had to remove the drive hub to chase the threads as I couldn't get a clean start on some of the holes. A look at the repair manual said "remove L.H. drive axle." Yikes! But no, it swings up high enough to pull the hub (drive shaft) out after undoing the 9/16" bolt. Whew! That's a big difference. Maybe they meant just to unbolt the inner CV from the hub, of course the GMC did that for me. Thanks alot.
After cleaning well and chasing the holes from the back side, I applied my favorite spline lube and put it all back together: 45 ft/lbs on the 9/16" shaft bolt and 65 ft/lbs and Locktite blue on the hub bolts. Didn't see any other damage other than a small dent in the tranny dip stick tube, so should be good to go.
Cheers
C. Boyd
76 Crestmont
East Tennessee
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| Re: So about that LH drive shaft.. [message #359889 is a reply to message #359883] |
Fri, 30 October 2020 16:27 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Shane,
I'm pretty sure it was Matt that wrote that the output shaft/drive shaft interface relies on friction from the bolt clamping pressure (bolts in pure tension) and not on the shear strength of the bolts.
The output shaft bolts are one-time-use torque-to-yield bolts and they're supposed to be torqued to 75 ft/lbs to achieve that clamping pressure.
I'm wondering if that 65 ft/lbs will be problematic.
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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| Re: So about that LH drive shaft.. [message #359892 is a reply to message #359887] |
Fri, 30 October 2020 21:04 |
Silvernort
Messages: 95
Registered: June 2019
Location: Rock Springs, WI
Karma: 0
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[quote title=C Boyd wrote on Fri, 30 October 2020 14:10]Sir, the outer CV end nut is 140-280 ft lb.
Um, OK. I didn't do anything with the outer CV end nut.
Shane Harvey
1973 26' "Packer Backer", 1976 Palm Beach, 1965 Dart
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| Re: So about that LH drive shaft.. [message #359893 is a reply to message #359889] |
Fri, 30 October 2020 21:17 |
Silvernort
Messages: 95
Registered: June 2019
Location: Rock Springs, WI
Karma: 0
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Richard RV wrote on Fri, 30 October 2020 16:27Shane,
I'm pretty sure it was Matt that wrote that the output shaft/drive shaft interface relies on friction from the bolt clamping pressure (bolts in pure tension) and not on the shear strength of the bolts.
The output shaft bolts are one-time-use torque-to-yield bolts and they're supposed to be torqued to 75 ft/lbs to achieve that clamping pressure.
I'm wondering if that 65 ft/lbs will be problematic.
Richard
I hope not, I know the manual says 75 but I was concerned with possibly stripping out the now-not-exactly-pristine threads. In fact one of the bolts gave me that vague greasy feeling at 60ft/lbs and I stopped there. The others were solid at 65 but as I said that was as much as I dared. 6 (ok 5) non stretchy bolts at 65 ft/lbs is hella lot clamping force. Enough tho? Don't know. My plan is to keep an eye on that flange until and unless I can come up with an alternative.
Cheers.
Shane Harvey
1973 26' "Packer Backer", 1976 Palm Beach, 1965 Dart
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| Re: So about that LH drive shaft.. [message #359900 is a reply to message #359896] |
Sat, 31 October 2020 15:42 |
Silvernort
Messages: 95
Registered: June 2019
Location: Rock Springs, WI
Karma: 0
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JohnL455 wrote on Fri, 30 October 2020 21:50I did not see the words “split washer” in your post.
Split washers have their place and I know GMC originally used them here but since I was using hardened bolts I decided to go the locktite route with mil spec flat washers. I went back and fourth with myself on this and here it is. YMMV.
Cheers.
Shane Harvey
1973 26' "Packer Backer", 1976 Palm Beach, 1965 Dart
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| Re: So about that LH drive shaft.. [message #359903 is a reply to message #359900] |
Sat, 31 October 2020 19:04 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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JohnL455 wrote on Fri, 30 October 2020 22:50I did not see the words “split washer” in your post.
Silvernort wrote on Sat, 31 October 2020 16:42Split washers have their place and I know GMC originally used them here but since I was using hardened bolts I decided to go the locktite route with mil spec flat washers. I went back and fourth with myself on this and here it is. YMMV.
Cheers.
I just have to jump in here because there is 40years of developments since the manuals were written.
The "split washer" type of lock washer was supposed to function two possible ways:
First - it was as a high load spring to retain then tension in the fastener so it would not unload with relaxation.
Second - the splits form barbs that intended to dig into the related components and prevent the backing out of a fastener.
Can you tell me which of these will not be a good application in our drive axle flanges?
The replacement fasteners available are not Gr.9. They are ASTM A574. McMaster-Carr is actually wrong on their 170KSI. To meet this specification they have to have a minimum yield of 180KSI. Gr.8 needs only 120KSI. If you attack one of these screws with a file, you won't get very far. That means that a split type lock washer will not be able to raise the burr that it needs to have to be any value at all.
As someone mentioned, these fasteners get part of their value from the friction of the clamping load. The tension in the fastener relates to the clamping load. Unfortunately, the torque/tension relationship in normal fasteners has a 30% scatter. This is why it was a very good idea that Shane quit pulling the one fastener that he thought might be yielding as he has no way to know if it is the flange material or the fastener that is yielding.
The good thing is that he glued them in. That means that apart from the relaxation that will occur, he will not loose the tension in the fastener.
I have a 23 and have little spare storage, but I carry what I might need to reinstall a drive axle because that is just not hardware store stuff and not even good parts store stock. I have local stores with bins of Gr.8 stuff, but I live in farm country and they might need it. These things are closer to aircraft parts. Yes, I have had call to replace mine a few times. The used one go in a coffee can and when I need something boring to do, I pull each one out and clean it off and compare the threads to a high quality tap. If I have any doubt that the fastener has yielded, it goes into the bin with the used valve springs and wrist pins. That does not exclude the OE parts either.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: So about that LH drive shaft.. [message #359916 is a reply to message #359903] |
Sun, 01 November 2020 13:30 |
Silvernort
Messages: 95
Registered: June 2019
Location: Rock Springs, WI
Karma: 0
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The fasteners I used are 180,000 psi hardened bolts. I doubted a split washer would dig into them, so elected to use modern chemistry to keep the bolts from backing out.
Time will tell...
Cheers
Shane Harvey
1973 26' "Packer Backer", 1976 Palm Beach, 1965 Dart
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