I have an 86 firebird 305 carburated, manual transmission. While i drive there is a metal grinding kind of sound icant really describe the sound but it sounds like a metal grinding as i drive. The grinding is in sequence with how fast im going. The grinding happens when i am driving but as soon as i let off the gas it goes away.

 

So the grinding is only when under load? Does the sound exist when the car is in neutral, coasting, stopped or in park?

 

Shot in the dark here, but maybe a bad bearing, like a water pump bearing?

 

Yea it happens when its just in neutral idling im thinking somethinf must just be lose somewhere on the vehicle because yesterday soundint like metal grinding but it now sounds like just somethint is loose and rattling

 

Has the flywheel been off? Flywheel bolts may be loose. Replaced a crankshaft or two due to this. Also had this kind of noise from water pumps. Try pulling the WP belt, see if the noise goes away. Try wiggling the fan to check the WP shaft for slop.

 

Sounds also possibly exhaust related.

Catalytic converter heat shield for example.

And of course, could be a bad motor or trans mount, allowing the whole thing to move around and something then rubbing. Drive shaft for example.