So I spent this weekend experimenting with my lift to see if I could rid myself of the rear drive line vibrations.
I first removed the front strut preload spacers and lost about 1" front of lift. I then removed the Superlift rear coils and lost 1.5" of rear lift. I replaced the Superlift rear coils with the BDS 3" rear coils and gained an extra 1/2" of rear lift over the Superlift rear coils. So with the Superlift rear coils gave me 3.5" of rear lift while the BDS rear coils netted me 4" of rear lift.
I had the truck aligned and took it out for a spin with the new set-up, no preload spacers and BDS rear coils. With this set-up every little bump would lock my belt and make it feel like my filings were going to pop out. This ride is rough as hell! At highway speeds it felt like I was strapped to one of those vibrating belt workout machines. (see image below)
Back to the shop I went. I then took out the BDS rear coils and put in the BDS 2" rear spacers along with the stock rear coils. This set-up rides fine until you hit 70+ mph then I have a little rear vibration.
I would say that the BDS 2" rear spacers and the BDS preload spacer along with the Superlift rear coils both have a slight rear end vibration at highway speeds. IMO the over all ride quality would go to the Superlift rear coils. The stock rear coils and 2" spacers are in second place and the BDS rear coils are harsh as *uck.
Now I don't need to see picture of your Quad/Crew cabs or RCLB with the 140" wheel base and telling me how great your truck rides. My 2012 Ram quad cab with a RC lift rode fine as well.
Next I'm going to see what happens if I remove the BDS rear UCA brackets and see how it handles. The RC and Superlift lift kits don't come with those brackets to adjust for rear pinion angle. Maybe I'll get lucky and it will ride better, if not I can toss them back on.
If you have a lifted RCSB with a 120" wheel base and want to tell me your experience by all means lets hear it. I have to say I can tear apart and put back together the rear kit in 1 hr and 20 mins now
With all set-ups the front of the truck rides great, goes straight down the road and zero steering wheel vibrations.
Edit: called BDS Friday 8/12/17 and left a msg. They're still ignoring my calls about my rear drive train vibrations.