need help looking for a seal for PVH..

[92 5 oh]

i've got a 98 ranger, pvh system. i've noticed that when it's cold and more specifically, when i engage 4wd i get a weird noise. it's difficult to describe, but it sounds kind of like a whirling sound and a squeeky wheel bearing. initially i thought it was the wheel bearing so i pulled the wheel off, i get no wheel play or anything so i don't think it's that. while i had the wheel off i noticed a shield in back held on with two bolts. i removed it and sprayed grease in there and the noise stopped for a few days. i also noticed that when i engage 4wd the t-case shifts immediately but sometimes the hub engagement is delayed, and it's worse when it's cold. so my suspicion is that there is some kind of rubber seal back there that keeps the vacuum applied until 4wd is disengaged. however i've yet to find a definate on this. i called the local parts stores and they didn't have a clue, the ford dealer didn't really know either, they told me my 98 hubs were not vacuum operated
so i've attached the best exploded diagram i can find. i believe i am looking for #12. does anyone have an experience with this? am i on the right track?

thanks!!!!!

 

[92 5 oh]

anyone?

 

[Original_Ranger84]

The seal really has nothing to do with the operation. If the hubs still engage cold or not it means they are working. They work by having an amount of vacuum put on the hubs (about 20psi to engage and 14 to disengage i think) and it holds that vacuum for about 30 seconds. When its warm the air is expanded more and the vacuum sucks faster, when its cold and the air is denser the vacuum takes longer to draw the right amount of psi... If that makes sense?

Basically its totally normal. Although I am curious if you got your hubs or whatever to stop making the squeeky whine sound cause mine do that every once in awhile and it drives me nuts!