Straining/Moaning noise between 4500-5500 rpm.

[rgkntulsa]

2002 Winstar. 3.8 liter engine. Makes a straining, moaning noise under hood when I floor it up an entrance ramp. Starts at 4500 rpm. Stops after it shifts to a higher gear.
No other problems. No dash lights. No leaking fluids.

Didn't notice it until I tried to sell car and test driver got into it up the entrance ramp.

Two mechanics said it wasn't transmission. One said it sounded like an air flow problem and replaced air filter to no avail.

[12Ounce]

The intake upper is a two-piece, clipped together, plastic construction in '99 - '??. At some point in time Ford began to make the two parts fused together. This was to eliminate a noise problem in the upper intake.

???

You might just remove the upper (14 screws) and take a look. If yours is the old clipped-together affair, a bit of epoxy should fix it.

[MT-2500]

Originally Posted by rgkntulsa

2002 Winstar. 3.8 liter engine. Makes a straining, moaning noise under hood when I floor it up an entrance ramp. Starts at 4500 rpm. Stops after it shifts to a higher gear.
No other problems. No dash lights. No leaking fluids.

Didn't notice it until I tried to sell car and test driver got into it up the entrance ramp.

Two mechanics said it wasn't transmission. One said it sounded like an air flow problem and replaced air filter to no avail.

I would keep it under 4500 RPM.
No need to reach that high rpm normal driving.
Automatic transmission should up shift before than.
What was he doing holding it in lower gears.
Most cars have a rev limiter that shuts them off before then anyway.
MT

[rgkntulsa]

This turned out to be a leaky rubber grommet with a small hole on the underside where the tube from the PCV valve goes into the air intake. The hole finally got big and leaked oil. When I fixed it the noise went away.