Drive line phasing question. 70 C20 manual.

[Chris_oz]

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.

[geezer#99]

pull off the rear shaft and rotate it 180 degrees.

[davepl]

Originally Posted by geezer#99

pull off the rear shaft and rotate it 180 degrees.

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...

[Bigdav160]

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.

[Roady’s truck]

Originally Posted by Bigdav160

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.

Or a u-joint is slightly off center.... didn’t you have to take apart a u-joint to change your carrier?

[geezer#99]

Originally Posted by davepl

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...

Balance!
180 because you can’t go 90 or 270 and stay in phase.

Sometimes it’s a quick fix.

[Chris_oz]

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.

[jeffahart]

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

[Chris_oz]

Originally Posted by jeffahart

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

That's a great tip. I am known to have a heavy hand (and body)
I will check it all tonight.
Thanks

[Roady’s truck]

Stiff u-joints will cause a driveline vibration.