Approx. 8 mths ago, my Honda which I have owned since new, started this strange behavior of suddenly ‘shuddering’ while at a higher speed on the freeway. This shudder would take some time to get started, maybe 10-15 min. driving and I would feel the shudder first in my foot against the gas pedal, then it would be more pronounced seemingly on the left front wheel. If I took the foot off, it initially would be relieved, but if I continued to drive, it would eventually get worse to the point I needed to pull over. I took it into our trusted mechanic, and he couldn’t reproduce the issue. He suggested and then did a wheel rotation/balance and the problem seemed to go away.
Recently it has come back and my husband who is quite knowledgeable mechanically did some inspections, and for lack of anything else, he asked our mechanic to replace the left front drive shaft. Well, it didn’t fix the problem. We are wondering what else could it be?
You need a new mechanic, it could be as simple as a gas filter or pump, but proper diagnosis for a proper cure, and wheel balance and rotation does not make my top 10 list of possibilities.
The problem might be with that front wheel bearing starting to fail. If your mechanic did the usual wheel bearing check by grabbing the tire at the 12:00 and 6:00 oclock positions and tried rocking the tire to check for a worn wheel bearing, sometimes that won’t reveal a worn bearing.
Have your mechanic put the vehicle on the lift, and with their hand placed on the strut spring slowly rotate the tire. Sometimes the roughness of the bearing can be felt in the strut spring when using this method.
Tester
I agree with Tester. It sounds like something is loose, and is finding its resonant frequency, leading to a shudder. The fact that it takes 10-15 minutes of driving suggests that it has to get warm before it finds a resonant frequency, which might also explain why the mechanic is having a hard time finding the loose component. All this points to a rotating component, and since you already replaced the axle, that pretty much leaves the wheel bearing(s), or the other axle.