noise when in 2wheel drive

i bought a 1996 blazer a month ago the 4wheel drive did not work it has 126000miles on it so i took the battery tray out to check the vac acut for the front diff it was rusted up so got it free and the 4wheel drive worked great but after i did this it made this vibrating nois from the frount diff only when in 2wheel if it is making the noise and if i shift it to 4wheel it quits complety then i shift it back in to 2 wheel and is silent for about 10sec and starts agen wat is doing this thanks!

Welcome to Automotive Forums kb3jhp :cheers:

If it didn't have the problem before you got the 4wd working my guess is that it isn't disengaging all the way

If you van reach the vaccum pot with the battery still in you might be able to give the cable a push and see if it moves in further

i have tried that before it seems to go in slighty but does not stay one odd thing is that if i pull the trancase lever just a littel it also quits i have put the transmision in netul and still does it put it in low does not do it i am thinking maby the cabel going to the diff do you no wat this cost and wher to get it wat else could it be thanks

also when i start when cold and rev slighty it sounds slighty like a knock or a disel i use penoil full sny and a touth gaurd filter could it be the filter do the touth gards have a check vaulve and if not wat ones do