Weird vibration in '97 Lesabre

97 LeSabre, 3800 engine, 157K miles. For the last several months, the car has a vibration that begins when approaching 60 mph, kind of a “thudududududududu” kind of thing, very rapid. Can hear it, but feel it more in the floorboard and steering wheel. Definitely coming from front end. Constant speed - does not change speed if I accelerate or slow down. If accelerate to 85 mph, the vibration fades out and things are fine. Alignment has been checked, not a factor. Have replaced tires with no effect. Additional weirdness - if I make a right curve/turn, it gets louder/heavier. Local mechanic is pretty good, hasn’t been able to pin it down. He’s wondering if something internal to the struts has maybe loosened or broken and is the culprit. I’m looking for a reality check before I pony up for new struts. Help?

If all the suspension components are found OK, then another suspect possibility would be worn inner constant velocity joint

Possible CV joints

I’m not a mechanic, so that’s why I’m asking, but would that still be a suspect even knowing that there is absolutely no variation in the rapidity of the vibration regardless of the speed? It fades in around 60-65 mph, it fades out by 85 mph, but the rate/period/rapidity of the vibration is constant regardless of speed or rpms.

I recently had a bad CV joint that did this - at least partly. It didn’t show up until about 65 and was pretty much gone at 75. I don’t know why. In my case, though it vibration was also very clearly tied to acceleration. In any case, as I read your description CV joint was also what I was thinking.

In case anyone’s still interested, we ended up replacing the tie rods and that seemed to fix it.