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#1 |
Registered User
Join Date: Sep 2018
Location: Newcastle, New South Wales, Australia
Posts: 139
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Drive line phasing question. 70 C20 manual.
Hi all,
On the weekend I replaced the centre bearing (tailshaft support) I was not thinking and didn't pay attention to the phasing of the uni joints between the front and rear shafts. I lined them up as I have always done, same as the attached photo,but now I have a vibration that comes in at 25-30mph and stays until 40,the comes back again at 50. I am sure it's driveline, it didn't have it before. Is there something different about the chev? It has the 465 4speed manual and stock 4.57 diff. I lined up the centre bearing central to the mount. The workshop manual only has larger truck shafts in it, no smaller trucks shown. Any tips would be great. |
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#2 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: Drive line phasing question. 70 C20 manual.
pull off the rear shaft and rotate it 180 degrees.
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#3 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Drive line phasing question. 70 C20 manual.
And if that doesn't work, try 90 and 270. That ought to cover it!
Geezer, can you explain why 180? Other than that reverses one segment...
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#4 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: Drive line phasing question. 70 C20 manual.
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#5 |
Registered User
Join Date: Sep 2018
Location: Newcastle, New South Wales, Australia
Posts: 139
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Re: Drive line phasing question. 70 C20 manual.
Hi all,
Thanks for the tips, I think I will pull the whole shaft out tonight and check the alignment again, I put it in as 2 bits and am eyeballing it, I think I have it, as if I was one spline out I am sure I would see the twist. But it was late and I was tired, so I will double check. I will also check the U-Joints for tight spots or play again, they felt fine, if not a little stiff. I am thinking that now I have the new centre bearing, the u-Joints are now showing signs of age which I didn’t feel before with the stuffed centre bearing, the rear uni (on the diff) is stiff to move, maybe it has some flat spots or issues, that I have made worse by removing it from its resting place of 49 years. I think I have found the correct U-joints to replace them if required. SKF 331, or moog 331, or Spicer 1350. All the same. 1 3/16” cup, 3.622 wide, external clip. My C20 is a 1970 Longhorn, with 350 V8, SN465 manual and Eaton HO52 (4.56:1) Diff All the websites I can find list this u joint as doing all three positions on the driveshaft. Thanks again. |
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#6 |
Senior Member
![]() Join Date: May 2012
Location: Scottsdale, AZ
Posts: 1,906
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Re: Drive line phasing question. 70 C20 manual.
Also, A reminder from "Inland Empire Driveline". It's fresh on my mind because I just got a new shaft and they sent a big red card with big fat letters stating:
Don't over tighten the U-bolts holding the shaft to the yoke or pinion. Too tight can cause drag and vibration thus causing heat. Torque to spec. But usually can't get a torque head in there so: Approximate by tightening till the lock washer flattens then do another 1/8 turn. j
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White K20 |
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#7 |
Registered User
Join Date: Apr 2011
Location: Klein Texas
Posts: 3,852
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Re: Drive line phasing question. 70 C20 manual.
The shaft's runout is compensated with weights.
It is possible to stack the weights all to one side causing a "stacked tolerance" issue. Chris, if you have your shafts phased properly and it still vibrates it is time to check the working angles of the shafts.
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My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe |
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#8 |
Registered User
Join Date: Sep 2018
Location: Near Decatur, Texas
Posts: 16
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Re: Drive line phasing question. 70 C20 manual.
Or a u-joint is slightly off center.... didn’t you have to take apart a u-joint to change your carrier?
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