famous 50 mph vibration ram 2500 2006 hemi 4x4

[erick85]

I own a Midas shop. Me and I my best tech usually solve problems others and even dealers can't find. It is a ram 2500 2006 with the hemi... I bought it a month ago. It is the famous vibration problem at 50 mph. Perfect when I bought it. Then I do needed maintenance like spark plugs, engine oil, front and rear diff, t-case, transmission, New pads and rotors on all wheels, New tires. Truck is still perfect, used all premium quality product. I bought a 7000 pounds fifthwheel rv, went away for 3 different campgrounds for a little less than a 1000 miles. Still perfect with and without the rv pinned or not. Then the vibration begins a morning when driving up to do some shopping around. I only made 1 mistake, I saw on all-data to put 70-90 in the rear diff only 1 model needed 75-140 out of maybe 6 so without double checking I putted the 70-90... First thing I did was to buy dealers oil 75-140 with the limited slip additive, wich my truck need after checking with vin number. Still the same. Did tire rotation and rebalance, changed the damper shock in the steering system, still the same. All parts on all the truck are tight and solid. Alignement is perfect. Nothing below 45 mph, at 50 it start vibrating and is at worst, then the faster I go the less is noticeable, but still there. 4x4 is engaging and disengage easely with the manual small arm, low 4 works great also, get the same result on hi-4x4. Does not go worst or better if braking or accelerating. Now i'm stuck. Gave every detail I can think of... HELP !!!! Thanks.

 

[Stangshcky12]

What kind of tires did you put on?
BFG all terrains are great tires but are known to cause death wobble on cummins because they have a softer sidewall and large side lug
It could be part of your problem even though Hemis aren't nearly as heavy

This could be from tie rod ends, sway bar links, ball joints, track bar etc.

 

[erick85]

Tires are Firestone transforce lt. Treads are not aggressive, bought them because i do a lot of highway and they have a soft drive for a lt. They easely reach 0 on the balancer. No loose anywhere.

 

[erick85]

problem solved... driving shaft to rear diff was slightly bent in the middle. was ok before and can't find a reason why it would go off like that... nothing to do with balancing, it took a 'banana' shape for no apparent reason.... probably was weak at a particular point.