Virtually every other thread has some mention of soundproofing. Today I saw a 6BT sump with what looked like polyurethane around the sump this was a factory part and the cummins tec put the No in quickserve for me to find out if the sound proofing was seperate or if the sump and soundproofing were one, sure enough the sump and sound proofing are one & the same. Does anyone know how much difference it makes? has someone heard both and can give me a 1st hand account? would it only be an advantage for a stationary engine? These must therefore be available for 4bt's. I suppose I could put something around the sump to quiten it, but is it worth the bother?