Driveline growl at slack throttle, thought I had it fixed, its back....8/19 update (2 Viewers)

landtank

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I'm interested to see how this goes. I have replaced both my shafts with DC Tom Woods. I have a recurring problem in the rear where my TC output shaft/bearing keeps becoming loose and I have no idea why, this obviously leads to vibrations (mine does NOT have a nut to tighten). I thought something might be wrong with the housing so I just replaced the entire rear housing and all components, fixed it for a minute but it's coming back slowly but surely! :( Maybe I need one of these in the rear instead of Tom Woods?
At the time I began talks with my supplier he had no 66x66 pin yokes. If they become available I’ll be able to supply DC rear shafts.
 
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Update: greased the slip yoke splines front and rear. The grrr at slack load is Greatly diminished. Looks like a new rear DS is in my future.
Y'all's got me so paranoid about over greasing the yokes I put back together with just a light coating.
 
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Skinny little blond one, fine as gossamer.
 
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Think I found my grrr but need to ask the collective their thoughts.
I changed the rear DS because of the tick-tock in the splines this past Monday.
The grrr at slack throttle is reduced, but it's still there and very much in the front, the passenger can feel it under their feet.
I crawled under it tonight and started looking for anything that would move that shouldn't.
Pinion bearing end of front drive shaft is dead tight, no movement of any kind, but the output bearing on the transfer case has a few thousandths of radial play. It ticks a little when the drive shaft is horsed up and down and I can see the output flange rock ( a tiny bit), I looked in the FSM and it appears to be a plain radial bearing.
Does this sound like it could be the source of the Grrr?
The rear output shaft bearing has a touch of play as well, but about half the front's.

If I pull the front drive shaft the Grrr goes away.
 
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Zjohnsonua

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HF2A/V has "runout" due to the design of the center diff bearing carriers (the flange is actually rocking a bit, rather than having true runout). Don't fret over what you found at the transfer.
 

heckler

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You probably have already tried this, but can you remove your front driveshaft and lock the center diff and drive around to see if the grr goes away.
 
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Pulled front driveshaft and it drives like a new truck, no vibes, no grrr.
I can feel the preload on the pinion bearings and the backlash and it feels just like when I set it up.
There is zero shake in the front diff. The whole truck wiggles when trying to find any play.
There is zero play in the front slip yoke.
There is zero play in the u-joints
There is a touch of shake in the output flange of the transfer case.
The angle of the output flange is +87.5
The angle of the diff pinion flange is +85.6
So the axel could rotate up an addition 2 degrees to make them //, which means I would be decreasing caster angle. That seems like a bad idea.

Is the 2 Degree delta between the flanges a major concern? What's the tolerance?

I looked at Tom Woods Driveline Geometry 101 - https://4xshaft.com/blogs/general-tech-info-articles/driveshaft-angles and I'm not sure a DC would work based on his explinations. If one were to rotate the front axle up to point the pinion flange at the transfer case, there would be negative caster angle. And obviously you can't tilt the transfer case at the front diff.

The only thing I can think to change, because it's the only thing I can find that moves, is the front output flange bearing on the transfer case.
Any other suggestions for things to look at?
 

mudgudgeon

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Front diff pinion isn't parallel with the trans pinion from factory. Diff pinion is angled up at the rear.

Have you had the front shaft re-checked for balance?
 
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No, but easy enough to do.
 
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The local transmission place took a look at it, has no idea what's wrong. All the usual suspects are new parts and tight as a nuns...er nevermind.
Agrees that the grrrr is in the transfer case due to location of sound. The owner and one of his guys looked at it, drove it around, both came to same conclusion. Or lack thereof, sigh. Good news is he didn't charge me any diagnostics time, so I dropped off a case of Modello and a couple limes to help combat this terrible late summer heat.🥵
Parts to rebuild the front transfer case output bearing shipped today. Should be able to get it fixed this weekend and see if the Grrrr goes away. 🤞
 
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The local transmission place took a look at it, has no idea what's wrong. All the usual suspects are new parts and tight as a nuns...er nevermind.
Agrees that the grrrr is in the transfer case due to location of sound. The owner and one of his guys looked at it, drove it around, both came to same conclusion. Or lack thereof, sigh. Good news is he didn't charge me any diagnostics time, so I dropped off a case of Modello and a couple limes to help combat this terrible late summer heat.🥵
Parts to rebuild the front transfer case output bearing shipped today. Should be able to get it fixed this weekend and see if the Grrrr goes away. 🤞
"where" does that noise sound like it is coming from in the cab?
 
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Right of center, front edge of seats, under/around the PWR/2nd start buttons.
 

Somebodyelse5

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For curiosity's sake... what height lift are you running? (measurements from hub to fender are helpful, as long as you aren't trimmed). What type of caster correction did you install on the front axle? Do you have your final caster numbers?

I've been doing a bit of reading and it seems that over correction of castor leads the need of a DC Shaft... but i am no expert and am sorting through something similar. Need to get my rig on an alignment rack and have some numbers.
 
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The lift tis 2.5 to 3" depending on the corner measured. The rear driver is the low one.
Delta VS 4 radius arms.
No caster numbers, never been on an alignment jig. Steering wheel returns smartly to center, so there's "enough".
Pinion flange and drive shaft angles are within limits.

This started after the re-gear; but not immediately.
It's as if changing all the bearings and tightening up diffs is helping to find the next weak link on a 265Kmile truck. Which, isn't all that surprising.
 

Somebodyelse5

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The lift tis 2.5 to 3" depending on the corner measured. The rear driver is the low one.
Delta VS 4 radius arms.
No caster numbers, never been on an alignment jig. Steering wheel returns smartly to center, so there's "enough".
Pinion flange and drive shaft angles are within limits.

This started after the re-gear; but not immediately.
It's as if changing all the bearings and tightening up diffs is helping to find the next weak link on a 265Kmile truck. Which, isn't all that surprising.

I think you may have over corrected your caster with those Delta 4" arms. In which case a DC shaft is how most folks solve this.

You *should* need about 2.5 degrees of caster correction with a 2-3" lift and that gets your drive shaft angles where they should be.
 

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