I have a 01 S40 with nearly 145K miles.

It had been running normally and then the other day, I suddenly started hearing vibration.

The vibration occurs at 35 mph + and gets louder the harder you accelerate. If I let go of the accelerator, the vibration disappears and it sounds normal. The vibration comes from the front and you can feel it on both the driver and passenger sides. I think there's more vibration coming from the driver side though ...

I've done the following:

- Alignment
- Wheels balanced/rotated
- Visually inspected the boots and they are not torn - they look ok

but the problem still exists.

What could be the issue here?

 

Have you ever changed the motor mounts (4 total)? Busted mounts can cause vibrations like you describe. Try this, with the car in park on a level surface, engine off, raise the hood and stand in front of the car. Place your weight against the front bumper and push the car. Watch the engine for excessive movement. It should move a little but not a great deal.

You can also crawl under and look at the 2 mounts on the center bar. On my 2001 the rubber had split such that you could clearly see it. You may have to remove the splash shield to see the front one.

 

I did change motor mounts recently - I believe I only changed 2 of them though.

When I had the motor mount issue, every time I went over a bump, it felt something was moving in the engine bay.

 

I also took a look at the tie rods and saw that there was some play there and needs to be replaced, but is that main cause of the issue above?

 

Probably.