Is this a normal noise for a C4
 

In second or third gear only, I can hear a chattering-type sound at 4K rpm's and higher. It won't make the noise in 1st gear and only above 4K rpm's in 2nd and 3rd....mostly 2nd gear. Has anyone else experienced this type of noise? I've basically ruled out engine timing due to the type of noise, and becasue we set base timing at 10 degrees, with a digital dial timing gun.

I had a Maverick back in late eighties w 302/c4 combo. I had 10 in convertor and turbo action manual valve body. The line pressure was so high that the cooler lines buzzed. I put the car up on stands and ran through the gears with someone listening and pin pointed to that. However it made the noise in every gear/ Might depend if you are still using kick down, and standard patern vb. Line pressure goes up as kick down moves/