I have a 2000 xterra se. I have a really bad vibration at highway speeds and have replaces the tires, front bearings , turned front rotors and rear drums since the problem started and can't figure this thing out. Have also checked the rims to make sure they were ok, and have checked front end componens to make sure everything was tight and is all ok. Appears to be also a humming from the front end and a thumping or growl from the rear. Any ideas?

Did you get the wheels aligned?? Were the tires properly balanced?? What size are the tires?

No have not had front end aligned yet. I have tried the original tires, 265/70/15, and the new 32x11.5x15 BFG A/T's on new rims, and had both sets balanced numerous times. Still have vibration. I am thinking of having drive shaft balanced as there is big round rusty circle on it , but not sure there was a weight there or not. Is about the size of a quarter. But running out of options before dealer bound for help. Not looking forward to their labor rates.

Just throwing in a thought. Drivetrains rotate based on the RPM's, so I wonder why you don't get it at other speeds? Have you noticed what RPM it happens at? Does it happen when you're cruising, or if you apply some torque to the engine, like giving it gas at lower RPM's? Wish I had more ideas.

Have you had the drive shaft lubricated as per the maintainence schedule? Differential oil changed?

It happens around 2500 - 3000 rpm's. But also noticed it get's worse on decelleration, so thinking drive shaft again. U-joints were all ok when I pulled it. But shop didn't have the time to balance it that day so haven't had that done yet. If balancing it doesn't take care of the problem then may be pinion bearing even though it doesn't appear to be loose or grinding at all. Have performed all maintanance on diffs and transfer case as recomended. I bought the truck a year ago and had all the fluids changed when I got it.

Also wanted to add , the humming from the front end was one of the bearings I replaced was bad. The bearing casing was weak and actually pressed in against the bearing itself. Returned it to the auto supplier and they said it was the third one the had returned for the same thing. They got a new shipment in and gave me a new one and also replaced the other side for me for free just to be safe. No more front end hum.

It might be a silly question, but are the rear shocks in good order? If they are failing and dampening at different rates they can cause vibration sometimes.

Shocks are about 6 month's old, so don't think they are the problem. Weren't really bad when I replace them, but went with a little stiffer one's for the trails I go on. But not a silly question either. I will have the drive shaft back tomorow, so will post whether balancing takes care of the problem or not.