More help with strange noises...

[Joe Kriston]

Ok,on both my '72 and my son's '69,I hear and feel a faint,tinny,body-echoing,sheetmetal-rumbling sound throughout the whole cab of the truck---but only on acceleration with the a/c on...Otherwise,they're both relatively quiet and smooth with the air off....Any ideas?....Both a/c's were recently serviced(by the same mechanic)...

[flyboy2610]

I would guess it has something to do with the compressor. Is the belt tension correct? The idler pulley isn't binding, is it? Remove the belt and see if it spins freely.

[Joe Kriston]

We even replaced the pully bearings,Flyboy,and they both do it....It isn't a real horrible noise,just a noticeable 'rumble' when the air is on,....Could be just because these trucks don't have as much sound-deadener as the new ones...

[flyboy2610]

Yea, it could be you're just hearing the compressor. Is the noise constant or does it come and go as the compressor cycles?

[Joe Kriston]

Its hard to say,....It's so blasted hot out here(108" all week)I don't know that I've ever driven either truck long enough for the compressor to kick off...You hafta remember,here in Phoenix a/c in a truck is a necessity,kinda like tires and a battery,...and not just a nice convenience for those guys like in those old Ford truck magazine ads with long sideburns and a Joe Namath haircut wearing a white turtleneck....

I'm half-wondering if the extra load isn't exposing some kind of worn rubber bushings---like cab mounts or something....Rubber parts do take a beating out here and I know the control-arm bushings on both trucks are pretty cracked and dried-out....