1999 Chevy Pickup metalic clanging when driven....?

Question

I posted a question earlier. let me state it is not the tranny, torque converter or plate, all these have been repaired or changed. It is a sound sort of like a fan blade hitting a metal shroud with a sort of squeak. it is loud on acceleration and will make the sound randomly in idle. the other day I was in reverse backing out of a drive, when I braked I heard the sound really well. It will always sound when driving (when torqued), randomly when idling. When in reverse and braking hard it really acts up. this has stumped several mechanics along with myself. We own a automotive parts business so we sort of know what we are doing. any help greatly appreciated, thanks everyone.....

Answer 1

check for broken motor mounts.

Answer 2

It sounds like you are grounding out on something. Lift truck and inspect around body to driveline area as there could be something touching somewhere which causes some very irritating sounds while driving. Could be some type of an exhaust or shield doing the same type of thing. If it is easy to reproduce, get someone to listen while loading the motor and try to pin it down to an area to inpsect while the motor is shut off. Was something removed and not put back, or was something installed and not tightened?

Answer 3

How about the heat/cool fan in the dash. Bad bearing and play in armature changes sound under acceleration/deacceleration. Or maybe a Universal joint going bad. But the drive shaft wouldn't be rotating when the engine's idling. Last thing I can think of is to disconnect the engine belts or spray water on them to see if it affects the sound.

Answer 4

I had a problem very similar to your's awhile ago. Is was a bad starter. The pinion on the starter broke free and would not retract. When accelerating the pinion would then bounce off of the flywheel.