Hello, new here but I have been driving Ford trucks since 1986, I have a question about my t-case. I have a 2005 F150 with a 5.4 and the manual shift t-case. A few months ago my turck has been making a whirling niose when you excelorate or decelorate but I don't notice it while just cruising. Today I chocked the front tires and put the rear on jack stands and noticed the with the truck in 2wd and the trans in park the front driveline will not turn, if you put the trans in nutral in turns freely. I started the truck and put it in drive and could tell the noise is coming from the t-case. I think the truck could be stuck in 4wd but with vacuum hubs they are unlocked. My question is with the truck in 2wd should't the front drive line always turn freely, I know every other truck I have owned they do but this is the first with vacuum hubs. This truck is my wifes daily driver so it is not abused in any way but I need it so stay dependable.

Thanks for any advice you can give me, Dennis