transfer case

I tried the general discussion and no luck so i'll try it here. Is it possible for the transfer case on my 96 Yukon 4x4 four door to be stuck in four wheel drive? The reason i'm asking is because my mileage has been cut in half since it snowed up here in Canada and I had to use my four wheel drive for a few kms. The switch on the dash flashes when going into 4x4 and stays solid when i'm using it. When i'm done and put it back into 2wd the 4wd light goes out and the 2wd goes on. The truck drives like it does in 2wd but it feels like it's fighting against something. New plugs, cap, rotor, wires, fuel pump, fuel filter and full fuel injection cleaning and flush. Thanks

strange...

maybe replace the fuel filter and check the pcv valve. they are like $5 each for the part at autozone. fuel filter is under the driver's seat, pcv valve is on the in the driver's side valve cover i think. if u remove it and shake the valve u should hear a ball rattling inside. if u hear no rattling replace yer pcv valve.

u could try checking your tranny, transfer case, and differential fluids

if u used a heavy weight oil that could make it strain more. or if it is wicked cold your oil could thicken considerably. i like castrol gtx 10w30 cuz its nice and thin but gives good protection.

do u hear it switch out of 4x4 when u hit the button? usually a noticeable clunk sound

thanks for the reply. I have replaced the fuel filter twice. I'll check the PCV but not sure how it affects gas mileage. I use 5w30 in the winter. I got a sneaky suspicion my parking brake may be ceased on as I used it for the first time right about when the mileage started sucking. Don't smell any burning brakes though and rear tires don't lock up. It's in the driveline shop right now so maybe they find something that isn't too costly.