Drive shaft vibes

I've been getting drive shaft vibes at 35-40 MPH. I got under and measured the pinion and t/c output yoke angles and they are:

Transfer case -7 degrees. Pinion +6.5 degrees.

I used an inclinometer accurate to +/- 1 arc minute. Looks to me that the angles are ideal. Should there be more difference between angles? The drive shaft yokes are properly phased and there are no dents or damage to the shaft. The slip yoke is nice and snug-no excessive slop. The vehicle is an 80 CJ-5 with 1" lift and 4.10 gears.

 

The factory specs for the rear shaft are 4*-6*, with 5* preferred.
This would be for a bone stock CJ5, no lift.
There are other possibilities as well: bent wheel, bent yoke, out of round tire, etc. Might want to check the amount of runout these components have.
Unless you can confirm it started right after the lift; then the angle might be your culprit.

 

I'm pretty sure the vibes are coming from the shaft. The vibrational frequency is too high to be tires or wheels. There always was some vibration. I think going from 3.54's to 4.10's just made it more noticeable. My friend came over this evening and brought me another driveshaft from the same year Jeep so I'm going to try changing shafts.
Thanks for the reply.

 

Sorry if this is too obvious, but a worn u-joint will vibrate before it fails altogether. If this is getting worse, the first place to look is the joints.

 

You can test this. Take out the rear shaft and go for a spin. And x2 on the worn out ujoint.

Karl

 

I got under there and grabbed the shaft near the joints and tried shaking it. There doesn't seem to be a worn U joint. Transfer case out put shaft and pinion shaft are tight also with no excessive play. As I posted previously, a friend gave me an extra drive shaft. When I remove the old one, I'll rake it for a spin in front wheel drive and see what happens before swapping the extra shaft in. Good idea Karl.

 

While you have it out check the yoke nuts for tightness. If I recall correctly should be about 150-175 ft lbs. Are the yokes on dshaft aligned?

Karl

 

Yes, I checked the yoke alignment and they are in phase. I'll have time after work tomorrow so I'll try swapping drive shafts and see if that works.

 

I tried shimming the transfer case down with 1/2 thickness worth of washers and it quieted the vibes down noticeably.