I actually have an 04 Sequoia, which is new to me, but a 2wd SR5 with 85k miles.

At about 55-60 a significant vibration occurs. It's low like a rumble or like a low bass note. It's consistent and never goes away until the exact second I slow down to the threshold. I've gone up to 75 and the vibration changes a bit, but it doesn't get better or worse, just different.

I replaced tires since they were worn and got an alignment (since they wore funny). Alignment mechanic said nothing looks really bad.

I've read a lot of issues about driveshafts, alignment of driveshafts, etc. I'm pretty certain it's not drivetrain related and instead driveline related. The engine/transmission have no affect on the vibration as going into neutral, flooring it, etc. has no affect on the vibration.

Also, it sounds like it's coming from the centerline of the car. It's more noticable/louder in the front seats or in the third row, a little quieter in the middle row (third row is on differential, front seats is closer to front of driveshaft).

What do you guys think? There are a lot of threads on here talking about differentials, driveshafts, etc, but it seems everyone's resolution is different. I'm going to take it to my independent mechanic next week. Finally, the vibration is pretty noticeable, it's not some small thing that only I realize. Just about anyone driving the car would comment.

Otherwise, car is perfect, drives straight as an arrow, is incredible quiet up until 55 mph. The only issue is this vibration, and I'm trying to determine the source of the problem.

Thanks

Did you check the u-joints? They should be loose or have slack.

could be rear end. Is there ever a clunk or clatter when accelerating on decelerating?

Not sure if you have a 2-piece drive line or not, but if you do it may be the carrier bearing.

Thanks. It's a 2wd, and I think it's a one piece. I thought it had the CV joints, but my friend put me in touch with his Toyota mechanic and he called me and said 2wd should have a U-joint. He thinks based on my description that it's the rear U-joint near the diff. He's going to take a look at it next week. He's seen that issue before on a Tundra.

My mechanic looked at it, and he said the U-joints looked great, but he noticed what he thought to be an area where a large weight fell off the driveshaft. We're going to have the driveshaft balanced, but I expect it's the problem given the situation. I'll keep everyone posted!

Good find. Hope that's all it needed.