Well i have an 04 trailblazer 88000 miles on it bought it when i had 75k never serviced the 4x4 system or have used it, we are planning on going camping this weekend so i tought id try the 4x4 last night ok turned it on 4LO and the truck acts like im running out of fuel kinda stalls and runs stalls not like its going to turn off but as if it had no power ok, so went into 4HI and everything seems to be working fine but dunno whats wrong anyone have a clue? also planning on taking it for a service whats the type of oil that i need?