Vibration issue investigation

[swivel]

I have been trying to help some fellow owners resolve vibration issues on 3rd gen trucks. Some have been resolved by the dealers (Tires, driveshaft, PS hose, bad mounts). There are a few that seem to be worse than others (always Quad cabs) and I have tracked down an issue that may be worth investigating. It seems that DC is using a very soft cab mounting system. The durometer of the cab to body bushings is very low and the design of the bottom bushing may allow the cab to "hop" on the mounts. I found 2 trucks with lower bushings that had a folded lip allowing more movement than designed (you have to remove a lower bushing to see the design). I have started experimenting on my truck by trying to stiffen the lower body mount bushings and can reduce cab movement by simply making the lower mounts more rigid. I'm sure that DC intended to reduce engine/road feedback to the cab by using soft rubber but it appears that it might be soft enough to allow the cab to rock/vibrate in a harmonic if conditions are right. The trick is to keep the cab isolated from frame movement/twist while not allowing amplification if other vibrations.

 

[HootieF]

2004 new truck

I have my truck in the shop for the third time reference to a viberation at 65-67mph. It very hard to drive long distances with this viberation. You don't feel the viberation at speeds above 70. What do you think the problem is. The dealer is giving me the run around and dosn't want to address the problem.

 

[swivel]

I have sliced up vibration into three categories for ease of reporting/describing. These are very general but help as a starting point. More detail is always needed (when is most pronounced?). These descriptions are mostly valid at "road speed" -roughly 50-70mph



1. A vibration that "cycles" about as fast as the fastest you can clap your hands together (about 5-6 "cycles" per second) - is usually unsprung weight related. This is mostly tire, wheel, brakes, internal axle and to a lesser degree driveshaft.

2. One that "cycles" at roughly 10-20 times per second can be driveline related - transmission, transfer case, driveshaft, pinion. Much tougher to solve since several components can contribute together to cause vibration. Can also be external engine component related.

3. What I call a buzz or hum vibration - this is the one that puts your hands/feet to sleep. Mostly engine related (power steering hose fix on 03's was one) Can also be related to items listed in 1 and 2 but usually related to a component that is spinning close to engine RPM.



Description 1 is almost always tires/wheels compounded with alignment (death-wobble is born here - properly defined as "castor shimmy"). Aggrivated by loose/worn stuff and lifts/big tires.



Description 2 is hardest to troubleshoot - it's a black hole to dealers since they can spend hrs and find nothing - and they get grief for trying to charge time back to mfg under warr for finding nothing wrong - all vehicles have some vibration/hum -the trick is to isolate the driver/controls. I think this is where most of our concern is.



I know several folks have found the driveshaft resolution effective - while some have not. This is why I am looking into what isolation system is used (body/engine/transmission mounts) and if they are working properly.

 

[DBoyd]

Are these vibration issues more prevalent in the 4WD or 2WD??

 

[HootieF]

It is number three and it is irritating when you drive for a long distance at 65-67 MPH. I was coming back from a BASS tournament 2 weeks ago and after 5 hours of driving I couldn’t stand it. I have driven a lot of trucks in my life but never had a vibration that just irritated you like this .

 

[HootieF]

Never put it four wheel drive!

 

[swivel]

it seems to be both but I think 4x4 Quad SB's feel it the most - however I have talked with several people new to pickups or 2500/3500's that are not familiar with "expansion joint bounce" or the general rougher ride that trucks have (especially when at max tire PSI unloaded). Most test drives are on paved roads and tainted with the adrenalin of buying a new vehicle -seems plenty smooth at the time. After the ink dries - you find that driving in the concrete freeway can't be done with a full cup of coffee ; ) But that's just what trucks do - especially 2500/3500's.



What I am after is the "jello effect" the soft rubber used to reduce harshness is having on changing the frequency or harmonic of what would be considered acceptable vibration. I believe that the top body mount is unloading under certain conditions and may be actually amplifying vibrations (of any kind).

 

[swivel]

HootieF,



Verify that you have a weight on your power steering hose (looks like a 2" long by 1/2" thick clamp). This was a vibration fix that was supposed to be added on 04's. Roughly a pump feedback to the wheel issue. I had it done to my 03 as a TSB and it made an improvement to steering wheel buzz. Yours should already have it though.



edit: I guess some 04's made it out without the new hose - link to tsb

http://dodgeram. info/tsb/2003/19-008-03.htm

 

[TTubb]

I have been trying to help some fellow owners resolve vibration issues on 3rd gen trucks. Some have been resolved by the dealers (Tires, driveshaft, PS hose, bad mounts). There are a few that seem to be worse than others (always Quad cabs) and I have tracked down an issue that may be worth investigating. It seems that DC is using a very soft cab mounting system. The durometer of the cab to body bushings is very low and the design of the bottom bushing may allow the cab to "hop" on the mounts. I found 2 trucks with lower bushings that had a folded lip allowing more movement than designed (you have to remove a lower bushing to see the design). I have started experimenting on my truck by trying to stiffen the lower body mount bushings and can reduce cab movement by simply making the lower mounts more rigid. I'm sure that DC intended to reduce engine/road feedback to the cab by using soft rubber but it appears that it might be soft enough to allow the cab to rock/vibrate in a harmonic if conditions are right. The trick is to keep the cab isolated from frame movement/twist while not allowing amplification if other vibrations.

Check out this thread. Perhaps it will help you. TT

https://www.turbodieselregister.com/forums/showthread.php?t=114685&page=1&pp=15&highlight=Vibration

 

[DPKetchum]

Had all of the above on mine. It was awful. Three things happened and it is GONE. Had TSB done on powersteering hose(most noticable differance)changed the exhaust(minor differance)and a few MILES(took care of the rest)13,500 on odometer now and after 6k it started feeling better. Mine would DO IT in neutral also at 1900 rpm to 2300 rpm.