First off, Hello I'm new to the forum. And I got a 88 k5 blazer with tbi 350, 700r4, np208, 10 bolts with 3.42s, And only 68,000 original miles woohoo.

It now has around 3 inch lift and 35s (they're stuffed under there)

Here's the problem when ever I take off there is a bumping comeing from the tranmission/transfer case area. It feels like there is a broke mount, but they all seem fine. Its only when I take off it goes bump bump bump then it stops once I get going. Any ideas what this could be?

 

have you checked the motor mounts?

 

yes i checked the motor mounts. I also checked the u joints.