I just re-geared to 4.56 about 3 weeks ago and have about 300 miles on it with easy driving no high load. About the middle of last week I noticed a vibration around 30-35mph. It gets stronger as speed increases, but is not accel/deccel dependent(it is speed based not throttle based). I tossed it up as a bad u joint. I ended up replacing it this weekend. Now the vibration is worse. I did some searches and found a couple threads stating it could be the pinion nut has come loose. I have rechecked both pinions and they are nice and tight. I do not have a sye. I do have a tc drop though.

It is just weird that it would develop randomly when everything seemed fine.

My plan of attack:
1. Remove front/rear ds to figure out which end it is coming from.
2. check u joints in front ds for play/slop
3. use gauge to check actual pinion angles.

Any other suggestions of what to check next or first?

 

Also motor & trans. mounts were replaced about 4 months ago. They do not have any cracks or tears in them either.

 

Check the angles first.

 

Ok I will thanks. An I checked for axel wrap last night. There is little movement from the axel when power is applied forward and reverse.

 

So I pulled the rear drive shaft on my lunch break and took it arround the block. It is still vibrating. After looking at the front. It looks like their is quiet a bit more backlask in in it than the rear. Could this cause the vibration I am having? There is about an 1/8 of a turn of the drive shaft befor I can feel the gears make contact vs about 1/16th of a turn in the rear.

 

Having almost the exact same issue, just been too cold to investigate

 

I pulled the front drive shaft after work. On the way home I noticed that the vibration was nearly gone. However it was still there at about 50mph now but a lot less severe. So I will rebuild the drive shaft an see how it feels. Will update after I reinstall it

 

Rebuilt the drive shaft and reinstalled it. The vibes are still there. It looks like I have a little in and out play on the transfer case yoke. It's about an eighth of an inch could this bee the problem? And is it just a bad bearing or is the shaft damaged. I can see if it was up an down it being a bearing. But in and out?

 

Are you running lift blocks? Please say no.

 

No I am not.

 

Pics of rear angle...



.

I also noticed on the freeway after 65mph it vibrates from the rear but only while on the gas. This is without the front drive shaft in. With the front in. It vibrates from 35mph up.

 

Anybody, with a suggestion please speak up there are a lot of views but only a few posts. I'm getting frustrated with these vibrations. I have also just checked the front back lash and pinnion drag/preload an both are good. Next is to replace axle u joints but I doubt that is going to help.

 

Looking at the pics you have posted I would say your driveline angle is off, hence vibs. I needed to shim axle by 2 degrees so the yoke/shaft was pointed down more. My suggestion would be install a SYE. Check the Tom Woods Site, lots of info on there regarding proper driveline angles.

 

But why would the vibes appear 300 miles after a re gear when there were no vibes before? I get that the drive shaft is spinning faster, but initially after the regear there were no vibes.

 

Where did you get the gears installed?