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Discussion Starter #1
Hey guys if you go through my old threads you'll see that my old driveshaft blew on the freeway and took my trans along with it. I put a new trans, new 1 piece rear driveshaft, and new driver side rear axle shaft and hub bearings in in the past month.

As soon as I got the truck running again I started feeling a gnarly vibration in the shifter and in the seat at 55 mph, and 65 mph. At 70 mph i could no longer feel the vibration in the seat but no matter what the shifter vibrated violently. Beyond that, it doesn't vibrate on acceleration or deceleration or in neutral, it just vibrates at 55+ no matter what I do.

I learned that my driver side axle was bent a few weeks ago and finally got around to replacing it a few days ago hoping that would solve the issue. Well, it didn't. I jacked up the rear end and could clearly see that at 55 mph the driveshaft was vibrating.

My suspicion is that something besides the driveshaft is messed up, because how could a brand new driveshaft be off balance right? Either way I'm gonna take my driveshaft down to a driveline shop on Friday and have them figure out if it's off balance or not.

My question for you guys is what do I do if it isn't the driveshaft? Could it possibly be transfer case related? Could it possibly be differential related? I just don't know where to go from here if my driveshaft comes back clean.
 

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Transmission mount in right place? loose/ broken?
 

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May also wanna check to see if your pinion nut is tight, this can also lead to vibration.
 

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Discussion Starter #5
Just throwing it out there, is the driveshaft correctly phased? Might be worth a peek at the motor mounts.

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Good question, I don't even know what that means so I would appreciate some education on what that is.
 

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Discussion Starter #6
Transmission mount in right place? loose/ broken?
I'm pretty sure everything under there is good and tight, i guess it couldn't hurt to double check. I'm pretty positive I've got the trans mount in the right place, there's only one way to bolt my trans crossmember together to get everything to fit.
 

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Discussion Starter #7
May also wanna check to see if your pinion nut is tight, this can also lead to vibration.
I'll have to double check that, what should the proper torque spec be for the pinion nut?
 

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Good question, I don't even know what that means so I would appreciate some education on what that is.
When the u joints on a driveshaft line up, it's considered in phase.
Some people take it to mean u joint angles and other things, but what I'm referring to is how the yokes are clocked in relation to each other.

Trying to explain without pictures is kinda difficult, but imagine this. If you were to remove the driveshaft and lay it on the shop floor, on the yokes where the u joint caps press in, would they line up? If it was put together out of phase at the slip, it will cause vibrations.

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