Hey Guys,

I have a 2000 Silverado RCSB 6.0 swap... I'm experiencing a thump that I can feel under the drivers side floorpan when shifting to 2nd gear (transmission shifts pretty firm)... Doesn't do it at light throttle but it doesn't take wot to feel it either. It also does it about 60% of the time when launching. What I feel is exactly like a broke transmission mount would feel but that has been replaced. I also think a broke motor mount is not the problem due to the fact I can stall, lightly launch, etc and have no problems. The truck has a 6'' flip kit if that matters.
Any ideas?

Thanks!

 

Have you checked that all of the bolts and nuts in the crossmember are tight?

 

I have... They're good. I recently did a converter swap and am wondering if the leaf springs are flexing that much. Not sure that I would feel it in the floorpan though. Don't have any traction aids btw... Thinking about assassin bars soon. Any other ideas? Thanks for the help!