Vibration at 55 mph only? Or when it goes faster. Or even when it goes slower but just not as sever?
I would suggest it's a front end component, but you said it was just aligned - which the machines wouldn't pass if it was a component being bent.
Couple quick checks for you to do. Stand about 20 feet away from the front of your vehicle with it parked. Now look at the jeep from the front. Do your tires appear to be aligned straight up and down, or slightly tilted inward or outward? While you are at it - check the back tires in the same manner. The vehicle should be straight up and down, as jeeps don't tend to involve camber into their steering mechanisms. I don't expect this is the problem though.
My first gut feeling is it's mud. Do you use the vehicle offroad? Maybe drive through some undeveloped roads where the roads have been wet lately? Mud can cause the tires to become unbalanced, and thus throw off the steering. I would double check you don't have anything inside those rims of yours. (Check tire pressure too cause you're at it anyway) Also watch for a flat spot on the tire itself - if a vehicle stays parked for long periods of time in hot conditions, the tires themselves can warp and create flat spots that cause the tire to become out of round.
The other suspicion - extreme long shot - brake caliper drag. I doubt this one very much because the vibration would also be present at slower speeds and your brakes would feel a little off when you applied them. That said, when I first bought my jeep the guy I got it from had never had his brakes done since factory (Some 170,000 kms later.) Yeah. Brakes were slightly worn in a heavy manner. This caused me quite a lot of vibrations at many speeds.
Sunday, June 8th, 2008 AT 4:49 PM