2000 Altima "Jiggles"?

[stocker2000]

From about 100 km/h and up (i.e. highway speeds), my car "jiggles": there's a nasty little side-to-side vibration that affects the whole car (not just the steering wheel).

Assuming the alignment and wheel balancing check out, is there anything else that could cause this? Something in the transmission maybe?

[elwesso]

Id check wheel balance and the rotors... Even if they really dont feel warped, they may be warped enough...

[stocker2000]

Checked both wheel balancing and alignment. Both are OK.

The sensation I'm getting isn't in the steering wheel (which I would expect if I had a front end problem). I seem to feel it more in the seat of my pants; an overall car vibration. Makes me think the problem is at the rear, not the front. I'll have to check my drums, make sure they're ok, too.

If anybody else has anything to offer on my theory, I'm more than happy to hear it!