98 Ranger driveshaft binding

I have a 98 ranger 4x4 xlt supercab with 93k miles.The problem is that @ various speeds when you accelerate you feel what is like a hard shift,this happens at no specific speed or time and It happens enough that it's a concern especially when you have to get on it to pass or pull out in traffic.The dealer say's it a driveshaft binding problem, that occurs over time and the only way to fix it is to install an aluminum driveshaft (500.00$).Has any body else encountered this problem and if so any ides on how to fix it..Thanks

the original fix was a new drive shaft - about 3-6 months ago ford released a new repair kit - a tube of grease and 2 clamps - price is about 30.00 - remove the shaft - use special grease - reassemble carefully not to get the driveshaft out of phase and reinstall - fixed (F87Z-4K277-AA ford part number for kit)

Does this grease go on the yoke that inserts into the transfer case or does it go in the boot that looks like a mini cv boot? Thank you

the boot