hope this helps
I have a 95 jimmy4wd Mine would make a whinning noise and as I would slow down would go to a grinding like noise. If I would put it in 4wd hi it would sometimes go away but would return later. I found out on trouble shooting this that the vacuum port on the transfer case was on the port wrong. there is a small notch on the port plug that you must line up right or you will be pulling vacuum on a port that you should not be pulling vacuum on , you might, look into that. mine had three vac hoses on it. one is actually a vent tube for the transfer case. I foun this out because I was trying to see why my 4wd was taking so long to disengage and i looked at my vac diaphram under the battery tray and discovered that my diaphram was not totaly actuating and traced the vac hose back to the port on transfer case. put the vac port plug on the right way and it has been working fine with no more noise ever since.
