I just took the truck to a British auto specialist, and they actually commented on the fact my driveshaft Ujoints look new, so now I'm wondering where/what the vibration is that I'm experiencing. Any thoughts on the matter?

I ordered a new driveshaft but I can use that as a spare if it turns out I don't need that right away.

 

The dudes at the British Auto place I go to used Dexcool. Though they said there are no leaks. I kinda wish they didn't.

 

I posted not too long ago about my driveshaft. I have had a few since my truck is lifted. Anyway, the u joints on mine looked fine, too, but I heard chirping. To be sure it was the driveshaft I removed the front driveshaft (9/16 wrenches), engaged the CDL, took a short drive, and there was no chirping. With the driveshaft on the ground I found that I could make it chirp just by manipulating it. It wasn't the u joints. It was the centering ball (in the middle of the double cardan end of the shaft). You can sometimes, but not always, see damage to the bearings on the u joints that is sufficient to cause chirping. I couldn't visually see anything wrong with the centering ball and it was definitely bad.

In either case, the earlier advice is certainly correct... If you hear chirping either immediately pull over or drive slow enough that you can tolerate the damage of a flailing driveshaft. I drove forty miles at 20mph once with a bad shaft since I had no choice. It sucked. I used the time to check the Internet and order a new shaft.

Lucky8 is a great place to buy anything, and a forum sponsor, but definitely a good source for driveshafts.