My '01 Ranger just crossed 295K miles but I'm worried that it won't make 300K. Perhaps the rod bearings are getting thin? I'm starting to hear a faint knock at certain times:

- for less than a second on startup, especially after sitting for a day or two.
- when driving on light throttle and low/no load, between 2000-2500 rpm.
- on light acceleration beyond 2000 rpm.

When accelerating hard and at high speed there is no noticeable noise. Nor at idle.

If it is a slight rod knock, how long would you reckon I have before rebuilding is required? Are there any other, non-invasive tests I can do to make a good diagnosis?

This truck is mission-critical for me. It get new oil and filter every 4K miles. I'm on a limited, fixed income, so getting a new engine or short-block installed is not an option.