Shaking at high speeds.
 

If I drive over 70mph, my car starts to shake.

At first I thought the vibration was strictly from the driveshaft as I had a worn center bearing. I replaced it with a 1 piece driveshaft and I still have the same vibration.

The whole car shakes but I don't get much vibration through the steering wheel.

It has done this on 2 different sets of wheels/tires so it's not a balancing issue.

Any guess what else it could be?

Check for play in any of the bushings, ball joints and the tie rods... wheel bearings are another possibility. That's where I would start anyway.

Does the car pull to one side or the other at all? Any heavy or uneven tire wear?

Wheel bearings are only a month old on both sides so I doubt it's that.

No play in front end. I haven't really checked rear end since the wheel bearing install but when I had the car up on hoist last week to tighten up e-brake, I didn't notice any play when I was turning the wheel.

Maybe slight uneven wear on tires, but nothing serious enough I'd even consider pointing my finger at. The tires are not cupping.

The car does not pull either.

As you know, sometimes it doesn't take much at all to throw everything out of whack. If you have any items which have play but not much make a note of it as a couple problems may be complimenting each other.

Pull the calipers off to ensure that the glides are not sticking.

If it only happens under load I'd add checking the subframe, diff, half axles and transmission output shaft to the list.

Oh, and check the PS rack.

That's all I can think of...

Took car up today up to highway speeds... and a little beyond.

I think it can be better described as a vibration rather than a shaking.

I used to get a banging noise from the center bearing which was fixed when I changed to a 1 piece, but now I'm noticing a clicking noise when going on/off gas which I'm assuming is from the differential.

Will a worn out differential cause a vibration? I can definitely see how if I have worn out differential bearings maybe it'd cause a problem but I'm having a hard time seeing how a worn differential may cause an issue.

If it's the differential, what kind should I replace it with? I saw OBX on ebay for cheap? :x:

I'm pretty sure a bad diff would do it, but it would be much worse when under a load as the problem would have to be pretty bad. I'd start with inspecting the brakes.

Brakes as in rotors?

I've never had a problem with rotors ever before until I cracked mine once on my RSX on the track. :rolleyes:
But that was vibration only under breaking.

It seems like the car vibrates when accelerating, off-gas, or cruising in neutral.

No, you're right about rotors, unless they were phenomenally screwed up they'll only cause issues when braking. I said the caliper glides aka guides, slides or rails. If one's sticking a bit the caliper can twist and apply more and more pressure (uneven) the faster the rotor moves. It's easy to check, pull the wheel off and unmount the rotor... if it doesn't slide on and off smoothly then take the glides off inspect for pitting, clean them and the caliper openings thoroughly, relube and mount them. Take it for a spin. It happened to my rear right caliper before and it took me forever to figure out what was going on... the wedge like pad wear finally clued me in (not to mention the difficulty getting that one caliper off and on).

Anyway, it's cheap to check it out.