vibration/shudder

[harleydavidsonstroker]

hey guys im new here ive owned my 2006 f-350 for 4 years now and i love it best truck out there put over 70 000kms on it without any real issues till now. it has a 6 inch procomp lift since ive owned it and no rear problems till i upgraded the kit.

2 months ago i had the ford garage install new procomp traction bars on the back to take away the axle wrap on hard launches and they also installed new set of 8" procomp leafs in the rear, now it vibrates off the line worse then it did before but goes away once it hits 2 gear but on the highway it vibrates from 70 km/h to 110 km/h also, at highway speed it feels like a tire coming apart

its been to the ford garage 4 times since and they keep telling me the driveshaft is out of balance...i bought all new u joints i will be replacing these in the next few days hoping itll fix it but what do you guys think???

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