This is a DDECII 60 series engine.I started hearing this sound which seems like a valve tap in a regular 4 wheeler.It happened 4000miles after going to speedco.I am wondering if a different oil filter might cause this.I may be wrong but it seems to come from almost where the bull gear/compressor gear etc. is located.Oil pressure and driveability is fine.Truck is in the shop and I will find out tomorrow.
Is this also related to my intermittent fan clutch belt screeching?The fan clutch was replaced 14months ago but my mech said I may just need to tighten the belts.

 

I bet on the bull gear.

it would only take seconds for your mech to check fanbelt tension. but ...if the belts are glazed. if it has been slipping for long; i would change out the belts, then adjust to proper tension.

 

I should have mentioned this before but I came on here with bullgear issues a year ago and this same mechanic changed the compressor,idler and bull gear.Maybe my mistake was using one from the yard.He actually purchased it from the yard per my instructions.We had the truck idle for almost an 2hrs and there was no signs of the noise.

 

Drove 250 miles today and no valve tap noise.
I will keep monitoring.

 

Sometimes what seems like an engine noise is a clutch assembly rattle. I had this issue ever since I bought my used International in 2007. No one was able to find the source of this ticking/tapping coming from the engine. Naturally, financially speaking they were not motivated: i did a top-set, then a couple of other expensive checks/upgrades and it was only after a year that one good mechanic finally found the actual reason. We went on a test drive and when the noise began he asked me to depress the clutch pedal by half an inch and ... shock! the noise disappeared! He climbed under the truck and put a couple of bungee cords on the clutch assembly. Driving has been a joy again ever since