High Pitched Engine Noise

My engine constantly makes a high-pitched turbo-like whine like it's revving too high, but the RPM's are OK. I replaced the air filter and it helped a little. I need this truck to last a lot longer. Any suggestions? The noise is directly proportional to the RPM, and it runs fine with decent acceleration for a 4 cyl.

 

Are you sure it's the engine? My truck is manual and is very high pitched in 1st gear with high rpms and I'm pretty sure it is just the transmission making the noise. If your truck is manual it may be the same thing.

 

have another person rev the engine while you stick your head in the engine compartment to pinpoint the noise, you can even remove the serp belt/s to eliminate any accessory pulleys....

 

How many miles? Might be looking at a water pump with bearings that have had enough. My Ranger made a high pitched metallic sound that changed with RPM just before the weep hole in the water pump started peeing. I couldn't tell the bearings were going out by trying to wiggle the fan until I took the belt off.

 

Possibly the fan clutch?