Vibration

[Hx16457]

So is there something I could have missed swapping rear ends that could cause vibration?
You just connect everything back and it should be good right?
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[Big Fenders]

Usually you would index a drive shaft when doing rear end work [mark the drive shaft in relation to the yoke] but on a complete rear end change I don't know...but the problem might end up being drive shaft..
Bob

[MARTYZ]

Did the rearend come out of the same model truck, make sure the pinion angle is the same, maybe a bent axle, just a couple thoughts

[MARTYZ]

Check the drive shaft to see that the yokes are in phase (same position on each end), possible to get out of place if te slip yoke was off the shaft at any point

[Hx16457]

Originally Posted by MARTYZ

Check the drive shaft to see that the yokes are in phase (same position on each end), possible to get out of place if te slip yoke was off the shaft at any point

I had put the drive shaft back in and drive the truck after I had it shortened! There was no vibration only noise from the rear end! Thus the swap!
But I can check that just to be sure!
Thx for your reply and input!
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[TBONE1964]

What is the condition of the new rear end? Was it rebuilt with new bearings?

Possibly a bad wheel(axle) bearing or pin bearing. Did the caps fall off the ujoints when you removed the driveshaft from the yoke? Sometimes a neddle will fall out of place.

Just my thoughts.

[Hx16457]

Originally Posted by TBONE1964

What is the condition of the new rear end? Was it rebuilt with new bearings?

Possibly a bad wheel(axle) bearing or pin bearing. Did the caps fall off the ujoints when you removed the driveshaft from the yoke? Sometimes a neddle will fall out of place.

Just my thoughts.

Just another old rear end! Not a rebuild! Yes one cap did fall and I can check the pins! Thx that is easy enought too!
Thx for the reply!!!
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[luvbowties]

Originally Posted by Hx16457

Just another old rear end! Not a rebuild! Yes one cap did fall and I can check the pins! Thx that is easy enought too!
Thx for the reply!!!
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If you find a needle is missing from the bearing cap, you can mic one and then find a drill bit with the same size diameter, cut(grind) it in two, grind length to match, and save(delay any rush)buying a u-joint. Sixty cents vs. $16.00.
sam

[Hx16457]

Originally Posted by MARTYZ

Did the rearend come out of the same model truck, make sure the pinion angle is the same, maybe a bent axle, just a couple thoughts

Yes both were 72's, I still have the othe axles I could swap them and try that, easy enough! Thx for the reply
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[Hx16457]

Okay, back to the vibration;
The drive shaft is in phase, checked that and I am good! Thx!

I pulled the driver side rear tire off and backed the brake off on that side, after I drove her I walked around and touched the wheels. That one was a bit hotter than the others.
Next I carefully reinstalled the tire and made sure the lugs seated properly, loosened the lugs on the passenger side and seated them too.
Crawled underneath and added some grease to the rear u-joint!
Next I grabbed each of the rear tires, one at a time, and tried to rock them back and forth/in and out checking to see if there was and play/slop... None!

But I did try to spin the rear tires while in the air and it will turn easy then get harder, then easy and harder....thoughts? Recommendations? (Yes it's in neutral)
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[Captainfab]

Sounds like you need to determine whether the tightness is in the brakes or inside the differential. Try removing both drums and turning the wheels again.

[Hx16457]

Good idea! Dang I should have thought of that! I just had those tires off!
The good thing is I still have it up on the jack stands though!
But if say the tightness is in the rear and not in the brakes, what then?
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[tincan1966]

When does this vibration happen- I mean at a specific mph? Is it worse while accellerating or decellerating?
I ask because I had a '69 C30(427 bbc, TH400 and 14 bolt dually rear axle) that I fought a vibration on for some time and posted in the forums about it. My situation occurred at around 55-60mph, worsened at about 65. I did all the same things you did.
I installed a new rear axle, shortened the drive shaft(rear section of a two piece)

We finally solved my problem when found out that the transmission tail shaft and the pinion yoke were not the same angle. The PO had installed a 1/4" shim between the trans mount and crossmember. Apparently there was a difference in pinion angle from the HO72 I took out and the 14 bolt I installed. I removed the shim, put in a new trans mount and problem was solved.

Regardless whether you have a 2 ujoint or 3 u-joint driveshaft, the transmission output and the pinion angle have to be the same.

[Hx16457]

"55-60mph" exactly!
heck The 700r4 I just put in had 2 washers between the mount and the tail shaft (it was on the trans still when I got it) so i just put them back between the mount and the tail shaft (assuming they were needed), but they might not be!!! dang I have to get that drive shaft out and check that angle! Thx. Tincan1966! you might be on to something!!!!

[Rich 5150 69]

Just a thought sinse you said they had spacers under the trans mount, ensure that the bolts holding the trans in place do actually tighten up so that there is no play, a trans moving around will cause the same issue.
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[Hx16457]

Originally Posted by Rich 5150 69

Just a thought sinse you said they had spacers under the trans mount, ensure that the bolts holding the trans in place do actually tighten up so that there is no play, a trans moving around will cause the same issue.
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Got it!
Thanks for the input!
I'll check it while am under there!

[luvbowties]

Another easy to do shot in the dark: rotate u-joint 90 degrees at the diff'l flange and test-drive.. Then 90 degrees more.....then 90 degrees more. All this assumes rear u-joint is symmetrical--not a "trick" joint with different size caps.
sam

[Hx16457]

I removed the spacers from under the trans! The bolts do tighten up all the way ( thx )
Checked the angles and I believe now I have it all correct.
I did spin the rear with the drive shaft removed and it spins freely.

I need to test drive her now, (out of time), so I had to stop for the day!
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[Hx16457]

Pinion angle corrected and now smooth running! Ended up with 5* down tail shaft and 5* up rear dif.
So after questioning all my resent work it was some thing that I just assumed would be fine as a 72' rear is (or so I thought) a direct swap for the 65'. Just goes to show me that because it should be doesn't mean it is!
Thx everyone!
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[MARTYZ]

Time and money will fix anything, Glad to hear you got it figured out with out too much expense, just a bit of time and we all learned a little along the way too.

[Rich 5150 69]

Glad it's all worked out now....
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