Cruising down the road today, my driveshaft FAILED!!! There was a slight vibration that suddenly got worse, aroar then all hell broke loose all in a matter of seconds. My driveshaft RIPPED IN HALF!! The u-jointswere/are still connected at the transmission yoke and pinion yoke. You guys with the vibration problems take notice. I fully believe this was due to the driveshaft hitting critical speed which is what I had believed all along is the major cause of the vibration complaints. This is something I have been researching for months and now I'm kicking myslef in the a$$ for not having a new driveshaft built about 2 months ago like was recommended to me by a driveshaft manufacturer in Dallas instead of putting it off. I gave him the driveshaft specs, rotation speeds and other numbersand he said the stock driveshaft would fail. I took pictures with my camera phone and if they turned out worth a darn, I'll post later. The driveshaft is literly the thickness of afew coke cans wrapped around a cardboard tube. I am not BS'ing you! I was able to peel the aluminum with my bare hands it is so flimsy. Now I have to go through the dealership hassle to try and get my truck repaired. A new shaft with the proper thickness of aluminum would have run about $350. My dumb-a$$......
EDIT: Ok, got the pics in. The top one is the front 1/2 of the driveshaft after I walked back down the road to get it. It broke off of the trans u-joint from stress but you are looking at the middle of the driveshaft. This is where is sheared.
After looking at the s#itty way this shaft is made, I am truly suprised it can withstand the normal torque to simply move the vehicle.

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are there different driveshaft for different weight classes and engines?

what years have this cheap shaft?

 

I wonder if the 4:56 gears had something to do with it? Its to my understanding that you can tow more weight with lower gears (ie; 4:56) which gives you more torque. Maybe the extra torque is too much for the 1500 pound driveshaft? Just a thought...doesnt the 2500 trucks with 4:56 gears have heavier duty driveshafts?

 

That's rediculous!!! Now I am gonna keep a closer eye on any vibrations that may happen!!! Good luck and keep us posted.

 

Paul has a good point....maybe it is the 4:56 gears. How many miles did you have on the truck?

 

I have an '03 with a turbo. My dealership replaced my driveshafter under warranty...even with a turbo. They said they replace so many driveshafts because the internal material cracks up that they could replace mine w/o any red flags going up to cause anybody to second guess my turbo causing the problem or not.

 

The only thing the 4:56 gears do is increase the critical speed of the driveshaft which is what got me started on the research I have been doing. Problem is when I contacted Dodge about the tested critical speed of the shaft from Spicer, I was told this was propritary information or information that was otherwise unavailable and they suggested buying the FSM. So, I did and there is no info on the driveshaft. I contacted a specialized driveshaft manufacturer in Dallas that builds them for big trucks. After giving him the information I could get on my shaft, he said with the 4:56 gears I was approaching my critical speed if I approached xxxx rpm's which was somewhere around 80-85 mph (give or take) although my vibrations started at 78 mph. After doing the math, I just assumed I could hold off on replacing the shaft for a little whileand just keep it about 70 - 75. Obviously I was wrong.
My buddies 03 2500 has a very thickwalled steel shaft but he also has the diesel which does not approach the rpm's we approach in our gas trucks. At 70", a steel shaft would warp at the RPM's we approach.
Driveshaft rpm math is final drive gear/engine rpm's. In my case .67/2500 rpm's at 70 mph = driveshaft RPM's of 3731. Weassumed the critical speed somewhere around 4000-4100 but we could not get difinative answer from Dodge on the thickness of aluminum used which playes a large part in the critical speed of the shaft. This is also whay they put speed limiters on these trucks. The limiter is set to keep the shaft from hitting it's critical speed.
I'm having an issue with BitPim trying to get the pics off my phone - of course.....
I knew the shaft was cheaply made but I could not believe what I saw. I'm still working on the pics.

 

Sure makes the hemi torque look good though! That surely is covered by the 7/70 power train??

 

Hopefully. I don't know if they are going to give me heck about the gear swap.
Service dept wrote it us as "customer complaining of vibration in driveline" (LOL)

 

WOW !!!! That totaly sucks....good info. I'm not sure what causes them to put AL versus steel. The diesel / Hemi doesn't seem to matter. My '05 2500 has steel (I know 'cuz it got rusty), my buddies '05 2500 w/a diesel had AL...weird ! What really tweaks my head is the fact that you can order 4.56 gears (allot of PowerWagon's come with 'em), so do they have a different shaft ?