Harmonic Vibration

[Frankenchevy]

Hey @Frankenchevy,

Do you notice this vibration at the same RPM when parked?
If only when driving, then after driving feel the hubs. If any hub feels hotter you likely have a bad bearing.
And, refresh my memory, what engine do you have?

I have an L31-R. I check the temp of my hubs pretty much every time I pull up to my front gate because I’m suspicious of them. They’re always cool-barely warm to the touch. I have replaced the front bearings, but haven’t got to the rears yet. The diffential shop said he’d do the rears for only $100 labor more while doing the diff.

 

[Frankenchevy]

Mine has similar vibration with 241, which is similar to 208 Seems like transfer case is in common. Or it's something in the suspension

What in the suspension do you think it could be? I’ll try anything, lol

 

[bucket]

Lol, I’m on it!

Does yours have an NP208? I’m wondering about the chain tension...

@bucket , does the truck that you experienced this in have a 208?

Nope, mine is a 2wd C20. BUT, my 208-equipped Suburban did have a minor harmonic vibration like you describe at speeds above 60-ish. But it was only in the winter months, when I would usually drive around with the front hubs locked.

 

[Frankenchevy]

Nope, mine is a 2wd C20. BUT, my 208-equipped Suburban did have a minor harmonic vibration like you describe at speeds above 60-ish. But it was only in the winter months, when I would usually drive around with the front hubs locked.

Gotcha, hence the hub recommendation you made. I’ll try pulling the hub locks tomorrow and make sure they’re unlocking. I’ll also try pulling the front driveshaft.

 

[Snoots]

Does your motor have a 1 or 2 piece rear main seal?

More sense here:

https://www.hotrodders.com/forum/alot-vibration-after-l31-swap-bought-new-flexplate-313977.html

 

[Frankenchevy]

Does your motor have a 1 or 2 piece rear main seal?

More sense here:

https://www.hotrodders.com/forum/alot-vibration-after-l31-swap-bought-new-flexplate-313977.html

1-piece. My flexplate is identical to the oem one pictured in that thread.

 

[Snoots]

I'm just tossing things out there (my 2 cents).

Pretty certain my issue is either rear driveshaft or x-fer case chain.

 

[Frankenchevy]

Is this squeaky noise and in/out play normal for a power steering pump?

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[Poppy 87]

There should be no end play whatsoever! That small/forward end of the pulley should be flush with the pump shaft.

 

[Frankenchevy]

There should be no end play whatsoever! That small/forward end of the pulley should be flush with the pump shaft.

Well I think that may be the source of my vibes. Last night when I got home for work, I fired up the truck and took it for a spin. When I got home, I put it in park revved it to ~2500rpm and sure as hell I felt the vibe. I thought I didn’t feel it in park before, but it’s there.

I pulled the belt and ran it up to the same rpm and it feels smoother. If my buttometer isn’t deceiving me, it must be something in the front drive. That’s the only item with a pulley with any play. I guess I’ll pull it and take it to Napa.

 

[Poppy 87]

Hopefully that will correct the concern. Beats a t-case or differential overhaul$$$

Sent from my XT1254 using Tapatalk

 

[gotyourgoat]

Well I think that may be the source of my vibes. Last night when I got home for work, I fired up the truck and took it for a spin. When I got home, I put it in park revved it to ~2500rpm and sure as hell I felt the vibe. I thought I didn’t feel it in park before, but it’s there.

I pulled the belt and ran it up to the same rpm and it feels smoother. If my buttometer isn’t deceiving me, it must be something in the front drive. That’s the only item with a pulley with any play. I guess I’ll pull it and take it to Napa.

Are you ******* kidding me? A pulley...

 

[SquareRoot]

That ain't it. Sorry to be a buzzkill but there ain't enough weight there to make a difference at 2500 rpm. Mine has a little play fore/aft. It would have to be radial play, not end play, to make a difference...or out of round.

That's my theory. Replace it and post back.

 

[bucket]

That ain't it. Sorry to be a buzzkill but there ain't enough weight there to make a difference at 2500 rpm. Mine has a little play fore/aft. It would have to be radial play, not end play, to make a difference...or out of round.

That's my theory. Replace it and post back.

I'm on the same page here.

 

[Frankenchevy]

That ain't it. Sorry to be a buzzkill but there ain't enough weight there to make a difference at 2500 rpm. Mine has a little play fore/aft. It would have to be radial play, not end play, to make a difference...or out of round.

That's my theory. Replace it and post back.

I'm on the same page here.

Well I’m hoping. The weird thing is it felt as though it smoothed out with the serpentine belt pulled. Either way, it’s a free experiment as Napa is warrantying the pump out due to play.