Back in the sixties and even seventies before oil went through the drastic improvement that it has seen, some people would add a quart of ATF at oil change to keep the engine clean. In fact in those days ATF was considered a magic elixer.

Since that time, however, oil has gone through drastic transformation. With modern, premium motor oil if you are changing it frequently enough, no additives are needed and in many cases can hurt.

That said, if you do have a problem with sludge, and if the oil has not been adequately changed this may very well be the case, you need to do a few short changes, preferably with a Universal grade oil. Universal is the oil designed specifically for diesels. It has much more detergent added.

If you were to change oil and filter using Universal, such as; Chevron Delo 400, Shell Rotella, Mobil Delvac, etc. Run it 500 miles and drain the oil while the engine is good and hot. Repeat this process until your noise goes away.

This is the safest way to "flush" an engine.

Good luck,