Vibration - Driveline Saga

fast 99

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Again, if it doesn't vibrate with the driveline disconnected (running on the front axle) doesn't this take those other considerations out of the picture?
It takes the front shaft out of the picture. Then it has to be something with the rear driveline. May be someone else has a suggestion. Rereading the OP you have tried quite a bit.
 

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I will run with the data your driveshaft is balanced and when you installed the u-joints you ensured they moved freely on their axis before installation; your driveline angles are accurate and the output of your transfer case is not worn out / leaking seal (telltale.) Check for "silly" issues such as stretched u-joint straps, or mismatched fasteners.
Finally...
With the pressure of the driveline against the rear differential, perhaps it is time to service the rear diff and change the oil - while doing that, inspect the rear bearings, crown & pinion, caps are secure and ensure all the ring gear bolts are in place.
 

dvdswan

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u-joints in phase with each other?
 

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Drive the truck at a speed just below where you feel the vibration, then drop the trans down a gear. If the vibration suddenly appears, it’s not driveline. It’s something related to engine speed.

If the vibration is engine speed related and not vehicle speed, you might also try reclocking the converter on the flywheel.
 

DBinWW

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Drive the truck at a speed just below where you feel the vibration, then drop the trans down a gear. If the vibration suddenly appears, it’s not driveline. It’s something related to engine speed.

If the vibration is engine speed related and not vehicle speed, you might also try reclocking the converter on the flywheel.
Thanks! That'll be today's project; that and popping it into neutral while vibrating.
 

DBinWW

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I've had brand new tires that had sidewall issues. Less than 10 miles!
It get's this rolling harmonic vibe... sure doesn't seem like tires. But... I should explore this more. Thanks.
 

R Carnella

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Had a similar problem until i found a bent axle
 

bft305

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have you checked/ replaced the engine and tranny mounts?
 

Scribbles

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I have the same problem with my 89 Suburban and have tried many of the ideas on here EXCEPT the suspension. I have changed the shocks to new nicer Bilstein ones but never thought about springs until now.
I have bought a new, used set of springs that are 4 inch lift but now they will be the next thing on my list to try since I need tires anyway.
I got frustrated and parked it in my storage yard for 6 yrs in the AZ heat and sun.
Thanks again for the great tips!!
 

SquareRoot

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What transfer case do you have? Is it a slip yoke or fixed yoke output? If its a slip-yoke output on the rear, have you tried replacing the output bushing?

You said you have beat the pinion angles to death, what were the measured angles?
This^^^^^
 

Snoots

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My Mom still calls me a 'bull in a china shop' but, she also says 'If it's broke, Roger can fix it.'
 

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