GM 5L40-E 5 speed transmission. A rather fragile gearbox (don't know a sv6 without a reco one). It is sealed/ no dipstick. Therefore I would suggest getting a mechanic to do a tranny service - should only cost a hundred and fifty bucks for new filter, gasket and oil. I wouldn't really bother changing the oil. I felt no difference when mine was serviced. And I think they're sealed for a reason...