bomber

I know that its a jeep and there will be some vibes and noise in the cab. However when ever I get above 55 mph I get terrible vibes and the noise gets so loud you can't hear anything. And as hard as it is to believe when I let off the gas and coast it gets even worse vibes and louder. I'm running 5.5" of lift with a SYE and a t-case drop. I just rebuilt both drive shafts, I've checked the hubs with tires on and off, no play in either. Both u-joints look good. Where is the vibes and noise coming from?

hankthetank

Axle joints? Ball joints? Track bar stuff? Alignment? Dunno I've had death wobble, but it wasn't that loud really. Transmission problem...motor mounts loose?

ZINGGG

A t case drop AND SYE? But... Why? An SYE is supposed to eliminate the need for a t case drop...

OMCOFFROAD

Check your yoke at rear pinion and see if its making contact. Also do you have degree shims on rear axle? You might want to try a set of 3 or 5 degree shims to bring up pinion angle. Even with SYE kit if angle is to much your yoke will rub on pinion.

bomber

The tcase is because the exhaust hangs to low for me to bolt it up snug. I would address that but bigger things keep coming up. It is shimmed, and I have a double sheer track bar that I recently tightened up. Would a worn pinion bearing cause it. There is no rubbing on the yolk from what I could see. Like I mentioned I just rebuilt both shafts and spent alot of time under the jeep. What about worn motor mounts, would they be loose enough to cause vibes and shaking while decelerating?

bomber

I know its not death wobble, I let go of the steering wheel and the jeep is as straight as an arrow.

jeepsurfer1

Corect me if I'm wrong but couldn't it be a loose trans case chain? (Rubing)

dogger15

That would be more of a clunking noise. Also if put the t case in neutral would be able to turn the ds a good amount

jeepsurfer1

Well I'm in the same boat 4.5 with sye... I'll check it one day but it stoped for a while after the sye now its back...

dogger15

Could just open up your t case and see if the chain is slapping. Also check your motor and tranny mounts

jeepsurfer1

Okay, I will once I fix my buddys jeep, thinks

bomber

Well I have had this problem for some time and am tired of it. I ordered some brown dog motor mounts and am going to replace the transmission mount, and hub assemblies as well. Where is a good place to get a chain for the np231 t-case?

TheNerd

Vibrations come from rotating parts. First thing I would do is try to isolate the problem to a set of axles/driveshafts.

1) Pull the front drive shaft. Have vibes?
-No? The problem exists between your front output on the x-fer case and the pumpkin. Could be u-joints, slip joint, pinion bearings, or just bad geometry (i.e. pinion angle).
-Yes?: Keep going.
2) Put the front back in, pull the rear, put the tranny in 4wd. Still vibes?
-No?: Problem exists between your rear x-fer case output shaft and the pumpkin. See #1.
-Yes:? Problem (likely) exists between the axles & the ground: U-joints, bent shafts, balanced tires/wheels.

If you still haven't found it, then you need to start looking at the x-fer case/tranny/engine rotating components and mounts. You can probably get these to show up by putting the Jeep in neutral (@ the tranny to test the engine, and @ the x-fer case to test the tranny) and bringing up the rpms while at rest.

To me, the added vibes under deceleration point to bad DS geometry (most likely the front pinion angle, but if your rear pinion is too high you could get the same result).

And just to round it all out, here is the standard DS geometry link:
http://www.4xshaft.com/driveline101.html

OMCOFFROAD

Ok have you checked your Harmonic Balancer? If the rubber is coming out of the balance or is missing this will cause a vibration at speed. Just replace one for a customer and it fixed his issue with vibration. Try that and the Brown Bag set up is nice installed some pretty clean set up. But check that

garb.man

Sorry, not trying to THREAD JACK here but i am replacing my harmonic balancer, i used an install tool, it seemed that i couldnt get any more turns out of it and it appears to be seated against the back, but the hub of the balancer is a touch past the face of the crank (where the bolt goes) is this okay or does the hub need to be flush with the face surface of the crank??