my 2000 blazer takes a while to shift into four wheel drive. on 2000 Chevrolet Blazer

It will not shift into 4wd drive while sitting in one place. most generally have to drive it for a while. If it doesn't go into 4wd, when I push the button to put it back in 2wd sometimes it makes a rumbling noise in front end.

Asked by for the 2000 Chevrolet Blazer
7301639 is the NAPA part # for the transfer case vacuum switch. Buy one and install it on top of the transfer case. That will take care of this! It is a vacuum actuated front differential or axle, and this switch tells it what to do. That noise you hear is the front diff/axle trying to engage or disengage but can't due to this switch which it is sticking internally but will finally free up and complete the shift seqence. Replace this switch! Or have it done.
Thanks for your help. I have one ordered.
You bet. I own a Blazer just like yours by the way! If this dosen't fix your problem, post another question and i will advise further. I am 99.9% sure of this repair though!
I think your right. I temporarily repositioned the actuator that is under the battery box. If I help the actuator pull the cable, it will engage the front axle. I had to do something with 14 inches of fresh snow and 30 mph winds. The new switch should be in tomorrow. Then I can put everything back in place. Thanks again.