I have a 2007 6.2 XL Denali with 148k miles on it. Truck was just gone through recently for a checkup and tuneup and they got her all us to par. I started to smell like a “heat” smell figuring it was burn off from fluids changed, new hoses etc so didn’t think anything of it and then…i was driving and white smoke started to come through the inside vent drivers side which smelled like maybe electrical but unsure. We pulled over and turned off right away opened the hood and clean as a whistle. Smoke went away and we could start it but would not go itto gear, looking under the vehicle there was a puddle which looked to be oil. Located in the middle right behind the front tires. Had to get towed because my truck would not go into gear. Stumped?
sounds like maybe a transmission line came off and blew the transmission fluid out, this will make lots of white smoke from it burning on the hot exhaust pipes. this will also cause you to not have any gears because the fluid is needed to make all the internals of the transmission work.
the fluid will be a red/pinkish color. to confirm I would get under the vehicle with a flashlight and look up, follow the transmission cooler lines from the front passenger side of radiator to the transmission. presuming this is the case you should see this fluid kind of all over everywhere.
presuming you didn't drive it far when this happened then the line can be reconnected and fluid refilled and you should be ok.
other possibilities are some kind of seal blew out, such as the transmission pan, etc in this case other repairs may be needed.
first thing to do is get a look under there and identify the fluid color and possible source of the leak
if the transmission line came off then the clip was not installed properly and the shop that did the fluid flush should be responsible for getting the line back on and fluids back in.
same if it was the pan and they had it off, if it's something unrelated to repairs then you may be on the hook for that.
