4th gear drive train vibration issue

I had a local shop install a new forged motor and now I get a pretty aggressive vibration which feels like it's coming from right below my right arm when its rested on the middle console. Dealer checked the drive shaft and said it's looks fine. Any ideas? It only happens when I let off the gas in 4th gear between 50 and 70mph.

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Quote from Dave@DDMWorks

Did they remove the transmission while doing the engine swap? Did you have a different clutch/flywheel installed at the same time?

Yes tranny removed & new clutch and flywheel and it only happens in 4th.

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Quote from Uglyrider954

Yes tranny removed & new clutch and flywheel and it only happens in 4th.

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I also had a laser alignment done yesterday at the dealer and i was unable to show the tech the vibration after he did it so I thought problem was solved but.... it started vibrating again shortly after. maybe the weight of him in the sling had something to do with It?

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Quote from MiM

Off topic... @Uglyrider954, did you ever get painted?

I did =)) looks amazing. No more textured plastic

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Quote from MiM

Nice!

Thank you!!

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