Greetings to all you Volvo fans. I just bought my first Volvo a couple days ago.
My wagon (automatic transmission model) has a shimmy under acceleration starting at about 55mph. I can cruise along at 70 or 75, and the car seems fine. If I punch it to pass a car on the freeway, the front end shimmies and the steering wheel shakes. It stops as soon as I let off of the gas. I can start out from a dead stop with full acceleration, and it won't start shaking until I hit 55 or 60.
Is this some kind of axle problem?

 

What's a shimmy?

 

Its like Jimmy with a 'sh' on the front.

This is going to sound really strange but do you feel like your not getting the power you think you should have when it shimmys? Reason being, I had this happen to me, it was a spark plug failure. Meaning a cylinder when dead under acceleration. I backed off and it was fine and I only noticed it on the freeway or around the speed your describing.

Second thing to check would be your front suspension. Tie-rod ends, lower control arm, etc for play.

Third would be the CV joints, if worn and under load they can move out of alignment and vibrate. Take your foot off the pedal and they pop back into place. Most of the time you can feel this happen because there is a clunk or you can feel a thud in the framework.

 

The shimmy is just like braking with a warped front rotor, the steering wheel goes left and right about 2 inches travel rapidly. The car seems fast enough while accelerating, and the plugs all look good. I have noticed a pop sound every now and then when making very sharp turns. That seems to point to CV joints. There is no play in the steering at all, which kinda rules out tie rods.

 

Can you rotate your tires and give it a try?

 

That's the first thing I did. Rotated the tires and checked the pressure, and still the problem persists.
Thanks for the suggestion.