New harmonic type noise

[Dieselnerd]

My truck has developed a new noise. Only under heavy load between 1600-1800 RPM when accelerating. Happens towing a trailer or with slide-in camper, not empty truck.



It sounds like vibrating sheet metal. Seems to come from the rear drivers side. The heat shield on the fuel tank seems tight and doesn't rattle when I pound on it. Nothing else back there.



Only other thing that has changed is I installed a one piece driveshaft earlier this year. That made the truck really smooth out at higher speeds and eliminated some earlier vibrations. So, unless that big aluminum cylinder of a driveshaft is "ringing" with diesel pulses, I'm stumped.



I might add, it's worse in Tow-Haul where the TC stays locked. And it's only in that narrow RPM band when the engine is really thumping.



Any ideas?

 

[HHhuntitall]

Sounds to me like you've self-diagnosed it..... try wrapping the driveshaft with rubber splicing tape every 12" or so, tightly 3-4 rounds, temporarily, of course. The rubber tape should help absorb some of the drone, making it go away or at least change tones, and tell you if that's it or not. Had the same thing in my old Dart with a stroked 440. The crank angle was off enough it caused the driveshaft to "pitch" under high torque. Wore the brass bushing around the slip yoke in the end of the transmission pretty quick, which finally told me where the drone came from..... Also have a '97 that would only do it at around 2300 rpm, ended up being the bed sheet metal where some spot welds came loose holding the bed to the crossmembers on the bottom sheets..... I guess time and off-road flex had taken their toll. I finally fixed it with a DewEze flatbed!!



And, just thought of it, I had an '03 in here, regular cab, one piece driveshaft in it. The driveshaft had been rebuilt previously in Fort Worth, Tx, but they didn't replace the slip yoke. It was wore bad enough in a certain spot that when the truck was loaded, it would vibrate a little. Ended up having to replace it AND the output shaft of the transmission to fix it. Loaded heavier or lighter, the shaft would slide in or out and not be in that one specific worn spot that caused the noise.

 

[Dieselnerd]

HHhuntitall, thanks for some ideas. My driveshaft was a brand new Mopar that came with new yokes, U's etc. so there shouldn't be any wear in the yoke.



The driveshaft idea was sort of thinking out loud, I should of added that the noise didn't start with the new shaft but two months later. It was still a change this year so I mentioned it.



The noise actually started in the middle of a trip after driving through a lot of road construction with some rough unpaved areas with the camper mounted.



Maybe I did break a spot weld or something came loose. I'll have to spend a little more time underneath pounding to see if anything rattles.

 

[JDKammin]

I was getting a vibration noise from my 05 on the way home from Texas. I looked at the front driveshaft a couple of days ago and found a u-joint going bad. I had the driveshaft rebuilt and now runs very smooth.