I went to look at a 97 3500 with a cummins for a friend, He is going to buy it but when it is running there is a buzzing sound that cycles on and off every few seconds. sounds like it is comming from the injection pump. Not very loud and it is hardly noticable. Anyone have an idea I posted in the 12 valve forum but looks like no one knows there.The truck really ran great but it has a bad trans and only 100,000 miles the guy wants 3000 I thought that sounded preyyt good. My friend that is going to buy it rebuilds trannys for a living.

 

A 1997 gasser with a V8 would cost a lot more and be a gas hog..13-14 mph... Depends on what he wants...if he puts a couple grand in it, he'll have a nice truck, good milage and no payments... Easy for me to say..
Don't know a lot about those later models... noise could be the injectors relieving... or something like that... Does a '97 have electronic injection?? I know they changed somewhere along there.. computers and stuff control the firing....

 

A '97 CTD is still mechanically controlled.