Weird vibration at 90-100 mph - doesn't exist with extra weight?!

[Sean]

Thanks for the suggestion's guys - I'll be finding out if it's the bearing soon, hopefully. ;)

[Sean]

UPDATE

So, I did some more high speed driving this weekend.

Out on the highway, and some other roads - some pretty loud/can definately feel in da butt, vibrations at 90mph and up to about 105. Pretty damn apparent.

On the way back from the hills, I realized that at certain RPM's, at any speed, there's a slight...rattle that comes from the rear. Almost like the diff is loose or something, and it's noticeable at that given load range.

I got udnerneath the car this morning, and everything is tight. I thought it might be the diff loose or a loose halfshaft - everything is tight.

So, here's another idea. Maybe my diff is low on fluid? Maybe it leaked some when I first filled it, and it's not full?

My other, and most likely idea, is that one of my bearings only makes noise at a given RPM. However, I changed the load ever so slightly, and the noise changed. This leaded me to believe it was driveshaft related or something around teh diff. I'm really at a loss.

I'm pretty sure the driveshaft is good, but maybe my u-joint is goin or somethin.

Just wanted to throw this up there. ;)

[Sean]

Did anyone have anything to add on this matter?

[Simon S]

Maybe my diff is low on fluid?

easy to check - pull filler plug and stick your pinky finger in there

I'm pretty sure the driveshaft is good, but maybe my u-joint is goin or somethin.

CSB condition ?

[Simon S]

oh - and i'd also rotate tires..

double-check easy stuff first

.

[AndrewBird]

Have you checked wheel bearings?