So my X developed a slight vibration between 13 to 20 mph. It happens when I take off from a dead stop and is more noticeable when I am on the gas more. I don't know if this is related to this, but I just replaced my radiator and did lose a little bit of tranny fluid that was in the tranny cooler part of the old radiator. I don't feel any slipping from the tranny in any other gear so that makes me think that it is not tranny related. I looked for a sloppy u-joint but they are tight and don't make any noise when I rock the truck back and forth. My boss said that I could have a u-joint freezing up on me. I am kinda stumped. Anyone else else have this problem before?

Check your motor mounts.

I checked my motor mounts with a friend and they are ok. I thought maybe my air pressure in the tires would contribute to the vibration, but when I aired the tires up a bit it made the vibration worse.

So I was looking under the X yesterday while at work and noticed something. Looks like I came down harder than I thought on my passenger side AC shackle at the Memorial Day run and bent the upper bolt holding the shackle to the frame. It pushed the bottom of the shackle towards the passenger side and looks to have pushed the rear axel out about an inch and a half. Looks like I have to get some new hardware and upper bushings to fix this. Can't really tell by the pic but the upper bolt is bent slightly.

That is a hard knock to have caused that.

Yeah I didn't think that I hit that hard. I ordered the new upper bushings from Nissan today, should have them on Friday. Does anyone know the size of the bolt that AC supplies with their shackles? I would really like to have new bolts and everything ready to swap out.

OK so I took apart what I thought was damaged. My upper bushings were bad but upon inspection of the bolt and sleeve, nothing was damaged. I still have the vibration and my axle is still pushed out passenger side about an inch. My friend and I were looking at the axle, leaf springs and all related parts but can not find anything wrong. I am officially stumped and may have to start taking things apart to see if something else is broke. I don't really want to take the X anywhere if I don't have to.