A 2pc out of the same bodystyle truck will work. Just need to build a bracket for the carrier bearing. I did it in mine, and it felt fine all the way over 120

 

What gears are you running?

 

So I mentioned this to every person I know that knows anything, and everyone of them told me that it isn't the driveshaft, that I'm floating the valves from running such a high RPM. And that to fix it I'd either need more trans gears, as in swap in a 6 speed, or go back to a higher gear.

 

If your getting valve float, you put in valve springs.. not another transmission...
Who told you that nonsense?

 

I agree, what rpm are you turning when this happens? Sounds like a driveshaft balance issue to me.

 

Its running about 3000 when it happens. As soon as I hit 85 it starts, and when it hits 90 its horrible. At 90 it runs about 3k. If it was a driveshaft balance issue, wouldn't I have the issue the whole time I'm driving? Not just at 90 mph and up? I have run 80 all day but motors turning 26-2800 rpm and no vibration issue. They said a 6 speed would help lower the RPM thus stopping the floating.

 

The reason you dont feel it at any other speed execpt 80-90 mph is because the drive shaft if fine at lower speeds (turning less RPMS) Its only made to go so much, and since you went from 3.23s-4.10s its turning a lot faster than it use to at 80-90mph. Trust what these guys are saying

 

You will know when it lets go.. believe me.

 

Alright well, I like to think that you guys know what you're talking about so I'm gonna give up on making this a go fast truck and just keep it as my dedicated parts hauler and DD and finish my 350. It's plenty quick like it is anyhow. Swapping the 4.10's for 3.42's. I can't stand to drive under 90 and this is pissing me off.