Vibration at 90 mph

[Stormtrooper Hemi]

So I recently discovered I have a vibration from under the truck starting at 90mph. I feel it in the seat but not the steering wheel. I'm thinking it's either the driveshaft or pinion nut. However according to the recall website my truck has already had the pinion retainer installed. It's an 05 dodge ram 2wd. Any thoughts

[Redtruck-VA]

With a vibration I would start with a dynmic balance on a high end tire machine that also analyses the tires roundness. I chased a vibration for 3 months. Turned out to be a couple of the new tires had hard spots. They would balance but rode like on train tracks. I rebuilt everything up to the actual tranmission main body including the tail housing. I couldn't believe new high performance tires could be the issue.
Story time: a buddy of mine kid brother asked me what I thought his high speed vibration was on his harley. I took it out and ran it up to around 100mph and told him I didn't feel anything unusual for a harley. He said oh, it's a high speed vibration.... that's when I knew he was messing with me....

[Stormtrooper Hemi]

Yeah it doesn't do it at any other speed. Just when I hit 90. And it didn't with my old tires and the new ones I just put on 4 days ago.

[Stormtrooper Hemi]

Sorry it did do it with the old tires

[Redtruck-VA]

Not for the faint of heart, jack it up on stands and spin it up.. look for something shaking..

[Stormtrooper Hemi]

Would the pinion nut cause it if it was never actually repaired for the recall

[Redtruck-VA]

Because of the relatively high speed, I would suspect the driveshaft. A drive line shop can spin it to check the balance..

[Ghost03hemi]

Has the truck been lowered?

[mikespeed6]

Check your rotors/drums for balance. I had a friend with a 1 ton with aftermarket drums that were close to 60 oz out. You can simply put them on any wheel balance machine to check if the pinion angle is correct and its not the driveshaft.

[kcd1369]

2wd or 4X4? If 4x4 check your front drive parts. Mine had loose CV axles that caused a vibration at 73 mph. but it smoothed out after low 80's. just another thought.