4x4 not working!

i'm sure someone here has been through this but i can't find the same problem in here when i search. when i shift my transfercase into 4hi or 4lo it won't go into 4wheel drive. i know the transfercase works because in 4lo i get 2lo, just no front wheels turning. when the truck is running and not in 4x4 i removed the connector to the vacuum motor on the axle and the black hose gets a good vacuum. from what i know, this is how its supposed to be. when i shift it into 4x4 the red hose should have a vacuum and the black hose shouldn't if i'm correct, but niether hose has a vacuum. i'm thinking it may be the transfer case control switch. anyone ever replaced one of these? i can't really see in there to see how it comes out. also wondering if i have to get bent over at a dealership for this part or if i can get it at a parts store.

[WILL]

Before you blame the switch, pull the supply line between the engine and switch at the switch. Make sure there is vacuum to the switch.

yep there's a vacuum from the engine, i think this switch is acting intermittently as once i managed to get it into 4 wheel. thought that maybe the lingake to the transfer case is not working properly?? but then it wouldn't turn the front driveshaft.

[RemyDodge]

I had a similar problem with mine this winter. It would go into 4wd as always, but didnt want to come out....took miles of driving before it would disengage. Turns out the black and red vacuum harness was just old and dry and one of the lines was cracked. I bought a new harness at the dealer...I think it was $30something. Works like new again!

[TomKat]

Yep, see a lot get swelled with oil and fail, especially on diesels.