Noisy acceleration

Noisy acceleration on my manual transmission…almost sounds like a plastic sack is lodged under the truck, especially at the higher RPM shifting point. But, when the gas pedal isnt being pushed, there is no sign of the noise. Help!

A 2001 F-150?

Is there a plastic bag under your truck???

Yuk Yuk!
I was hoping for a more serious answer.

To be honest i have never heard a plastic bag nosie from a truck or car unless there was indeed one under the car/truck

Noises are pretty hard to diagnose without hearing them, and just about as hard to describe. Someone else may have a different description of it, if they heard it, but here goes. Does it make this noise if youre sitting still, and just revving the motor? If you gas on it till it makes the noise, and then back out of it without mashing the clutch, is it still there, does the sound change if it is? It could be a loose piece of sheetmetal vibrating somewhere , maybe on the exhaust. I have seen mufflers start coming apart on the inside, baffles break loose, and make some wierd noises when you accelerate. Just a few things to check.

Got running boards ? Mine turned out to be a running board brace that had come loose.

When I back off the gas, the sound goes away. Hopefully it is what you are describing. I'll have the exhaust checked out. Thanks for your help!

throw out bearing?