Jumping/bumping rear end at 70kph

Our beloved 2006 Tacoma has suddenly developed a bumping (rear end) mostly at 70kph. Checked at garage last week, no worn/broken parts noticed. Needed wheel alignment will be done tomorrow. The frame was replaced under warranty a few years ago. New tires last winter. Any ideas?

 

Tire balance, wheel bent, shocks shot are all options.

Start by rotating tires F-R and see if the shake moves.

 

Could you better define "bumping?" Is it just a sound or can you feel it? Does it come on suddenly or do you transition into and out of it? Can you feel it through the floorboards, brake pedal, etc? Are you sure it's the rear end? The better you can characterize it, the more we can help you. That said, diagnosing noises over the internet is pretty difficult.

 

Tires have been rotated, balanced, hubs & brakes cleaned. Shocks new last year. Visual inspection did not show a bent wheel.

 

This is more felt than heard. On a smooth road at 70kph it feels like going over potholes. It cannot be felt through the steering wheel so likely not in the front. Above or below that speed it doesn't happen or is not noticeable.

 

If your tires are balanced then I'd say it sounds identical to cupped tires... Mine have done the same thing the last 5k miles, all 4 tires cupped pretty well and need replaced. at highway speeds the back end in particular vibes pretty good. So much so that the front passenger seat headrest shakes pretty intensely doing 75mph down the freeway.