One of mine went out on the rear driveshaft(47k miles), and yes, im ashamed to admit, I only changed the one, for now...
Didnt have time to jack with getting the other one and spending even more time beating the ever loving crap out of it, had to get to work:doh: (It was rusted in there pretty good, as well as just wouldnt come out with 5hrs of BFH blows)
It was trashed when I peeked under there, I had a vibration for two days on the way to work, on acceleration, went away on when you let off and coast, peeked under there and it was toast, inside of the cap had chunks missing, and grease was coming out.
I went with a 330A from napa(351A is for 6spds I believe), and FYI, it needs grinding to either the caps, or retainer rings to fit, its .010 taller than a stocker(could be .010 on either end, .020 total, but im not positive)
Youll see what I mean when you go to put the retainers in.
In the future, im going to replace the front one soon(front Ujoint, rear DS), and for the front driveshaft, im going to just buy a full replacement from mopar, and ill jack with swapping the Ujoints to greaseables later, but im not going to waste my time trying to pull the u-joints on it either, mine were practically rusted in, and I dont want to mess with changing out the CV joint either.(mopar replacement front DS is $200~)