I have a 91 F150, I6 with a 5 speed trans(don't know exactly what it's name is). When I let off the clutch and at low speeds in low gears there is a rattling sound coming from the trans. It has done this since I bought it 2 years ago(with 125k miles, now has 137k). Doesn't seem to affect operation, but was wondering what it might be.
noticed today that while making a turn at a stoplight, it made the noise. I was in 3rd gear and didn't depress the clutch. As I started to speed up it made the sound for a few seconds. Just seems to do it at slow speeds/takeoffs.

 

Problably the throw-out bearing.

 

peicemakers right but check the u-joints, look for rusty stuff coming out of them

 

thanks a lot guys. I'll check it out.

 

Gets my vote.

 

Sounds like normal gear whine which occurs when when the transmission is under load...like slow speeds in a high gear.

 

It's not gear whine. It comes directly from the tranny. I can even feel it in the shifter.

 

is there not a vibration dampener washer attached to the bottom of the shifter??? this could make the noise...

 

Not for sure. I can pull the boot off and check it out. It would be nice if it was that simple. Thanks for the tip