Im chasing down a vibration. I did do a search, plenty of post on vibration but, most have no answer on how they where fixed. The vibration starts around 75mph and gets worse around 80mph, other than that it seems smooth at all lower speeds.. Some of the things I have done to eliminate is new tires, rebuilt front drive shaft joints including centering ball. There is no local shop that can balance the front shaft in my area. I talked with the tom woods people and they say that even with all the joints replaced you can have wear on the slip joint portion of the shaft and that can result in high speed vibration. ON the back shaft the rotoflex has a couple very faint cracks in the rubber but, otherwise looks good and the u-joint on that shaft looks good, no movement in the joint. Any thoughts or experience with this is greatly appreciated. We are planning a trip to the outer banks soon and I need to get this fixed before hitting the interstate.

 

lol stay under 75.

balanced and aligned tires, front shaft and rear flex are the biggest common causes. lock the xfer case and remove the front shaft, see if that has any results, then you can at least narrow it down. but since uve done most of those things, id just change the flex at the rear, simple cheap job.

 

Thanks, the speed limits are 70mph, Ill get flat ran over if I stay under 75mph. Unfortunately I dont have cdl so removing a shaft and driving is not an option. I guess I will start with the rotoflex, it just doesnt look bad and i hate to throw $109 plus shipping at something if its fine.

 

How did you check your rear u-joint? Grabbing it and trying to shake it isn't a valid test. Baring obvious failure the only way to check a u-joint is to disconnect the propshaft (the transfer case end is enough) and check to see the u-joint moves smoothly in all directions.
A seized u-joint will cause vibration, though since it's over a narrow speed band I doubt that's the issue.

 

I just double checked the front shaft u-joint closest to the front diff. when holding the shaft in one hand and the joint in the other I attempted to twist in opposite directions and i actually got some movement in the joint. I repeated this with other joint and they did not move at all. I cant remember now if this joint was rebuilt or if it was just the double u-joint on trans side that I had done.

Does the rear shaft use the same u-joint as the front?

 

Yes, OE u-joints are the same. Dimesions are in my propshaft rebuild thread.

 

Should i have this slight rotational movement in the joint? I checked the joints on my truck that i rebuilt a month ago and it has the same slight movement when you twist the shaft opposite of the joint body.

 

You just found the culprit.
Just to be perfectly clear. We're talking about the part of the DS, with the boot going over a narrower DS then to the Universal.
There should be no movement between the shaft and the flange that the Universal is bolted on. If there is movement, it not good. Gotta replace it. If that front one ( of the front shaft ) lets go, that is the one that does a lot of damage.

FYI if you manage to separate the front DS from the splined part, it only goes on exactly one way.

 

Im talking about grabbing the shaft in one hand and the U-jont in the other and rotating in opposite directions, as if the car is going forward and reverse at same time. I have some very slight movement where the X part goes into the cap. Its slight but, my truck also does this with the new joint I just put on so I thought maybe its normal?

 

Yup. No movement ( rotational )between the drive shaft and where the Universal connects to.

Check and see that the Universal caps are mounted and the yoke holds it in place securely.

Only 2 places where it can possibly move and both are bad.

1. Needle bearings on the UJ are shot.
2. The yoke that holds the Universal is shot.