U-joints...

[Neohostus]

So, I've been told that because of how the U joints are fit onto the driveshaft that it's more efficient to just blow money on a new driveshaft instead of replacing them. I was told that they're compression fit and you can't just remove them and throw on new ones. I really don't want to spend that much money on something that I could potentially fix for much cheaper...

What do you guys advise?

[flyinglizard]

When I service the  center bearing and Guibo, I poor synthetic trans oil into the U joints. Take your time and wobble it in there. It may make some improvement.
 The joints are staked in. I have changed them, restaked them, and sent the driveshaft to a balance shop. It is about a 50/50  success rate deal.  You have to be very careful with a dial indicator to get the joint in the center. It run about 250$ for all of this.
 Check with your local truck shaft shop for advice. MM

[1991 E30 M42]

There is a company in Texas that "customized" a driveshaft for me, they put new ends on the sections that accommodate a stronger serviceable u-joint and they balanced it for $200, as soon as I remember the name I will let you know.