I am getting a slight vibration at 45 mph, I am pretty sure it's coming from the rear propeller shaft, but not completely sure.

Does anyone have a suggestion for diagnosing this and a remedy?

 

Could be that your flex coupling is going bad (the rubber thingy between the prop shaft and trans), have you climbed underneath and inspected the prop shaft?

 

did you have the problem before the "New rotoflex on rebuilt rear shaft & Rebuilt front shaft?
did you try pulling out one shaft at a time to see if it goes away?
Oh its an 03 doesnt have a CDL does it?
is it a woods drive shaft?

 

Who did you get the front shaft from, same on the rotoflex? Did the front shaft get a new centering ball? Have you also greased both front and rear slip shafts?
If they are good, then it could be tires.

 

Well I have the same shaft in the front, the rear shaft was used, one of the reasons i am assuming that it where the vibration is coming from. The old rotoflex was really bad when I bought it, so bad that one of the flange openings was almost twice the size. The tires are new and I just had them balanced.

I did replace the center ball (front shaft) and installed a new pinion flange (rear shaft). because it was in good shape I did not replace the bearing at the end of the rear propeller shaft. Both shafts are well greased.

 

If I remove the rear shaft and drive it to the speed I usually get the vibration 47 mph is this safe to do?

Once I have isolated the vibration to the shaft do I take it to a drive line shop to balance?

 

You have an 03 with a open t/case so you can't drive on just one shaft.
Have you even checked to see if the front has been rebuilt, as for the rear shaft, have you greased the 1 u-joint and is the rotoflex cracked at all?

 

Yes I just rebuilt the front one complete with center ball. I did not have this shake until I first replaced the rear because the vibration was so bad when I bought the vehicle a few months ago.

The first thing I did was take it to a tire shop and the tires are good. They noticed the rotoflex was torn up. the slip shaft was so dry it wouldn't slide, so I got a replacement shaft from my local junk yard.

I rebuilt the shaft, but it was not neccessarily balanced before I put it back on with the new ujoint and rotoflex.

Is it possible that the shaft is simply out of balance and a trip to the driveline shop might fix this?

 

Many salvage yards use large forklifts to position vehicles, and shafts do get dinged by the forklift. Driveline shop may be a good idea.