The vibration occurs at about 35mph on up to about 65mph. Worst at around 45mph.
the whole cab vibrates. No steering vibration. I checked for slack in the steering not too long ago. The idler arm has a small amount of play. I feel certain thats not where my vibration is coming from.
As far as I can tell they have never been separated. I know the truck was sold from a local dealer, the carfax only has that small wreck in it's report. I would find it hard to believe that there has ever been big issues (Chassis, engine or transmission) with the truck.

Is there any way to test and know for sure that it is a cracked TC or flywheel without before taking it apart? I'm gonna get back under there and look tomorrow with a better flashlight.

- - - Updated - - -

Actually, I just got back under there with a better flashlight and I cant see anything close to the center. As far as I could tell everything looked fine. The only thing I did notice was a small scratch on the TC that makes me wonder. The rest of the TC has a small bit of surface rust (it may not even be rust, but its not paint), but there was a spot that had a small scratch. If that TC was recently installed it may have received this scratch when someone set it on the ground, but I really find it hard to believe that it was installed recently. I know it wasn't installed in the past 6 months atleast. I figure that after 6 months, this scratch would have rusted over and looks like the rest of the TC. Not shiny..
I may be looking at something that doesnt matter, but I dont see how there could be any scratches on the TC at all, unless there is debree flying around . It is on the little part this is bumped out.the rest of the TC has a brownish color except for where it is scratched here and is silver.

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