Knocking vs "vibration" vs "drone" question

[Badunit]

I know this issue with vibrations has been brought up repeatedly but I'm still not clear on the syptoms others are experiencing and whether we're all talking about the same thing(s).



My truck has what I'd describe as more of a knocking sound/feel than I would a vibration at about 2000 rpms. It happens in neutral and every gear at the same RPM. It seems to build for a second or so; if I accelerate quickly through 2000 rpm, I don't notice it. It sounds similar to a knocking main bearing but I've assumed it is an exhaust resonance.



I've heard the word "exhaust drone" on 2nd and 3rd generation trucks but I don't know what that is. I've assumed it is a low frequency sound that slowly warbles (i. e. , gets quiter and louder from destructive interference of the various sound frequencies). Is this correct?



I've heard others mention a "vibration felt through the steering wheel and acclerator pedal". Is this a relatively high frequency vibration like a buzzing or a low one like a knocking? It's been mentioned that there is a TSB for this one but I don't know if it'll cure what i'm experiencing.



And, of course, some have a vibration at the mph that corresponds to 2000 rpms (about 70 mph). This is definitely not the problem with my truck but it seems to get lumped in with the "2000 rpm vibration" discussions.



My big question is whether the "vibration felt through the steering wheel" is related to what my truck is doing. I'd sure like to get it fixed but I don't want to waste my time with the TSB if it isn't going to solve my problem.

 

[Steve M]

I think you're right about the different vibrations being mixed up. Exhaust drone as I've come to know it through four trucks is a steady low humm that sounds like it's "in" your head rather than coming from outside. To me that's when the exhaust note becomes a drone. All four of mine from '95 to '03 have done it. When I have a head cold and I'm all conjested with "head in a bucket" syndrome, it's way worse.

If you have drive-line vibration as well, it'll cause the exhause drone to seem to pulsate as the two vibrations rythmically cancel each other out. Like two guitar strings out of tune with each other. Drive-line vibration is more felt while the drone is mostly heard.

Normal engine vibrations can be transmitted through any poorly isolated means into the cab. In '98 when Dodge went to the hydro boost brake booster, I noticed the engine vibrations being transmitted into the cab through the steering wheel, dash and windshield. It being a 5spd/4. 10, I was at 60mph in the drone zone. I hate it for 89k miles until I traded it for an '01. 5 auto/3. 55. I stayed under the 2100rpm drone zone up to 75mph so it wasn't bad at all. If I locked out O/D while towing in the mountains, it too vibrated and droned in the cab at 2100rpm and up.

Now my '03 produces the same vibrations and drone but, without the diesel clatter and thrashing at higher rpm, the vibration seems way out of place. That and the vibration is more pronounced in the '03. Maybe the new cab or the new frame might act like a tuning fork being stiffer and lighter.

With over 20k miles on the odometer, it's smoothed out considerably just like the previous trucks have done and it's down to a tolerable level. The only cure to it that I can imagine is and auto/3. 73 combination to keep the rpm under 2000 up to 70mph. A 5 or 6spd with 3. 73 in O/D is running right at the same rpm as an auto/4. 10 in O/D. With 1st gear being so low, a 3. 41 ratio would be ideal for the manual transmission trucks in my ever so humble opinion. Even better for automatics if you don't tow much.

 

[dieselpilot1969]

I tried something today, I took 4 or 5 large cable ties and tied the two power steering hoses together and dang, almost no vibe felt at 70

 

[rogerblind]

I wondered about tieing the two hoses together ... or tieing them to something solid nearby. Seems like that would accomplish the same thing as the TSB's ridiculous looking weighted hose.