Vibration while accelerating

So this just started a few days ago

5speed tranny bmr lower control relocation brackets and bmr drag springs.

Car is turbo makes 550whp.

I made a third gear pull and while decelerating a bad vibration happened and reverberated through the shifter really loud.

I drove next day and nothing out of the ordinary. It drive fine out of boost just slowly accelerating. In second and third when you hit boost and it access fast is has a vibration I can feel in the pedals and hear in the shifter. I looked at u joints they seem ok. Tranny mount is ok. Motor mounts look decent I will be changing them out soon as my k member shows up.

Only thin I can think of is the spec clutch that has 20k miles on her that was slipping on the dyno is maybe doing it. Like I said it doesn't do it under normal driving. I have a twin disk ready to go in but I'd like to pinpoint the problem before I have the car apart so I can fix all at once. Any thoughts?

Oh harmonic balancer looks ok engine revs in neutral fine

Stock driveshaft? If so suspect.

So I let it idle and warm up and the vibration is there at 3000 and up rpm in nuetral not very bad but it's there. It feels like it's coming from the very back of the motor by the bell housing

Bburns4667 said:

So I let it idle and warm up and the vibration is there at 3000 and up rpm in nuetral not very bad but it's there. It feels like it's coming from the very back of the motor by the bell housing

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Vibration in neutral definitely rules out a drivetrain issue so unless you've broken an engine mount (best case scenario), the most likely source is the engine itself.
I hope I'm wrong but I suspect you might have hurt the motor, especially if the connecting rods/pistons are stock. Possibly a cracked piston or two due to detonation. An easy way to find out is to remove the oil filler cap from the valve cover while the engine's idling. If it blows out oil vapors, combustion gases are leaking past the pistons into the crankcase. You'd then need to do a compression check on all cylinders to find out which ones have a compression loss.

It's a built bottoms end. I changed the flywheel and clutch to the twin disk the vibration is gone. The spec clutch was the culprit

Bburns4667 said:

It's a built bottoms end. I changed the flywheel and clutch to the twin disk the vibration is gone. The spec clutch was the culprit

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That's good news. Glad to hear it.