Front drive shaft vibration

[JAY1941]

Hello all, I’m getting a front drive shaft vibration while in 4hi, but only when I unload the drivetrain over 40mph. If I keep the accelerator pressed even slightly the vibration goes away. For it to happen inhave to be going over 40 and slowing down in 4hi. This is the only time I get a vibration. Can any of you offer some inside. I have a metal cloak 3.5 game changer and MC front drive shaft. My Jl is a 4dr rubicon.

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[word302]

Are the Metalcloak driveshafts balanced? You may have thrown a weight. May have to pull it and have a driveline so check the balance.

 

[AnnDee4444]

Read this thread: https://www.jlwranglerforums.com/fo...et-driveshaft-mega-thread…buyer-beware.88097/

 

[JAY1941]

Read it, didn’t see similar symptoms to what I’m dealing with speed wise. I’ll take another look.
Thank you.

 

[AnnDee4444]

Read it, didn’t see similar symptoms to what I’m dealing with speed wise. I’ll take another look.
Thank you.

Your vibration is almost certainly caused by using a driveshaft that mixes a CV joint with a double single-cardan. It is exactly the same problem that the lifted 392s are having.

 

[JAY1941]

Are the Metalcloak driveshafts balanced? You may have thrown a weight. May have to pull it and have a driveline so check the balance.

I did pull it and it looked okay, weights seemed to be good. I initially thought it might be a loose component that was only making noise when it wasn’t torqued but everything was tight as well.

 

[JAY1941]

Your vibration is almost certainly caused by using a driveshaft that mixes a CV joint with a double-cardan. It is exactly the same problem that the lifted 392s are having.

Okay, for some reason I though all double cardans used a single cv on the other side. Do you think it’s more that the joints can’t properly phase eachother out during deceleration?

 

[AnnDee4444]

Okay, for some reason I though all double cardans used a single cv on the other side. Do you think it’s more that the joints can’t properly phase eachother out during deceleration?

I mistyped... should have been single-cardan in the post above.

A double-cardan is a constant velocity type joint, while the single-cardan is not. Two single-cardans phased & angled properly will cancel out the variation in velocities, but only one joint will result in vibration in all angles that aren't close to flat.

This video shows two single-cardan joints. If one end is replaced with something that has a constant velocity (such as a double-cardan or rzeppa) then vibration is inevitable... especially at higher speeds. https://www.jlwranglerforums.com/fo...thread…buyer-beware.88097/page-8#post-2084808

 

[GATORB8]

Impacted by braking? You can check for U-joint/driveline slop by locking in 4 in park and attempting to rotate the front shaft both directions. IIRC Jeep must be running for the FAD to engage.

 

[CarbonSteel]

I mistyped... should have been single-cardan in the post above.

A double-cardan is a constant velocity type joint, while the single-cardan is not. Two single-cardans phased & angled properly will cancel out the variation in velocities, but only one joint will result in vibration in all angles that aren't close to flat.

This video shows two single-cardan joints. If one end is replaced with something that has a constant velocity (such as a double-cardan or rzeppa) then vibration is inevitable... especially at higher speeds. https://www.jlwranglerforums.com/forum/threads/aftermarket-driveshaft-mega-thread…buyer-beware.88097/page-8#post-2084808

Even with a working FAD?

 

[AnnDee4444]

Even with a working FAD?

OP stated while in 4-high.

Yes, with the FAD disconnected nothing spins... so no vibration.

 

[CarbonSteel]

OP stated while in 4-high.

Yes, with the FAD disconnected nothing spins... so no vibration.

Missed that part...

 

[JAY1941]

Yes

I mistyped... should have been single-cardan in the post above.

A double-cardan is a constant velocity type joint, while the single-cardan is not. Two single-cardans phased & angled properly will cancel out the variation in velocities, but only one joint will result in vibration in all angles that aren't close to flat.

This video shows two single-cardan joints. If one end is replaced with something that has a constant velocity (such as a double-cardan or rzeppa) then vibration is inevitable... especially at higher speeds. https://www.jlwranglerforums.com/forum/threads/aftermarket-driveshaft-mega-thread…buyer-beware.88097/page-8#post-2084808

I have a double car

I mistyped... should have been single-cardan in the post above.

A double-cardan is a constant velocity type joint, while the single-cardan is not. Two single-cardans phased & angled properly will cancel out the variation in velocities, but only one joint will result in vibration in all angles that aren't close to flat.

This video shows two single-cardan joints. If one end is replaced with something that has a constant velocity (such as a double-cardan or rzeppa) then vibration is inevitable... especially at higher speeds. https://www.jlwranglerforums.com/forum/threads/aftermarket-driveshaft-mega-thread…buyer-beware.88097/page-8#post-2084808

okay cool, I have a double cardan by the T case and single up front obviously but what’s the fix for that, if Incan get the flange on the fron axel more inline with the shaft it should lessen that I’d assume. Everything on the truck is brand new.

 

[JAY1941]

Impacted by braking? You can check for U-joint/driveline slop by locking in 4 in park and attempting to rotate the front shaft both directions. IIRC Jeep must be running for the FAD to engage.

Not braking, unloading the drivetrain above 40mph. So just letting off the gas at say 45mph will cause the vibration. If I give it gas or even just tip the throttle it stops. So I can drive as fast as I want without vibration until I let off the throttle

 

[Some Random Guy]

Dumb question, what are you doing in 4H at 40+?

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