"Well now that I think about it I did swap out my 1 overload leaf spring to the 3 pack overload springs that were on the donor truck so maybe since I got more spring power it won't move as much as before. But I did go ahead and put a zip tie on the end and pushed it up against driveshaft part that moves, so let's see what happens when I get her on the road."
Unless you have quite a long drive shaft, 3/4 inch doesn't seem like enough travel from empty to loaded and going over bumps loaded. If the slip joint is too short, that is, if the driveshaft is too long, the joint will "bottom out." The weak point is the spring center bolts, which will shear off the first time that happens; then the steering will seem very vague as if suddenly you have bad king pins. If that doesn't happen it may split the female part of the slip joint and you will discover that they aren't cheap. I had to buy one recently and got it for $75 used from the driveline shop. Also, rough shifting (often a problem with inexperienced two-speed axle operators) will cause the slip joint to get sloppy and then they vibrate like the dickens and will loosen all the screws in the cab and drive you nuts with the noise. Rough shifting is also hard on u-joints. A drive-shaft shop can point you in the direction of a pamphlet that tells how much travel you need and how to set up the u-joint angles for minimum vibration. Spicer publishes such a pamphlet. It's free.
Because you changed axles, you may have to put tapered axle-shims between the spring perch and the spring to get the angle to match the transmission angle. The u-joint angles should match within a maximum of 1 degree. Half a degree is better; that's the motor-home spec. Consider also what the axle angle will be when the overloads are fully engaged. If the distances between the overload perches and the overload-spring leaves aren't right, the axle will torque one way or another and the u-joint angle will change once you're set down on the overloads. So it may not vibrate empty but will vibrate loaded or vise versa. What is happening in this case is that the u-joints are fighting each other as their angles don't match. That will greatly shorten u-joint life no matter how much grease you put in.
