2003 dodge ram 2500 qc 4x4 auto, ctd,

Does anyone know why dodge runs a dampener on the slip yoke of the rear drive shaft, I had a bad vibration start at about 70mph, had the tires checked and rotated. Took off the drive shaft to have it checked and the guy calls me telling me how when he spins it above 2000 rpm (same rpm @ 70 mph) it starts vibrating like crazy and he believes it is the dampener. He says he can take off the dampener and balance the drive shaft. But i cant find any info on why dodge is using these, driveline guy reports he doesnt know.

 

you know. . .Ive always wondered the same thing. . .[&:]

I wonder if some computer model thru CAD showed some sort of vibration that it was needed.

 

If I remember right, you guys have the steel shaft. Due to the length, about 70",steel is not as forgiving as the aluminum and will flex causing a vibration or failure. Ask you driveshaft guy if he can determine the 1/2 critical and critical speed of the shaft and that may answer your question as to the dampner. If it's approaching the1/2 critical speed of the shaft, the dampner my be offsetting the effects. Then again, it sounds like your particular shaft may not need it if it does not vibrate w/o it.

Shaft speed is final engine rpm's / final drive gear. Critical speed will be determined by length, thickness, diameter,type of material and other factors.

In my case 2500 rpm's(at 70 mph)/ .67 (final drive gear) = 3731 rpm's on the shaft at 70 mph. This is not accounting for torque converter slippage.

I was thinking of having a new shaft made for my truck. It will run about $325 for a 4 3/4" x 66"diameter shaft made from thicked walled aluminum - can't remember the thickness off the top of my head.