Wait a sec...the Tracker uses air PRESSURE and not vacuum to engage 4wd? This probably explains the noise I heard when I engaged 4wd a few days ago when we hit some snow--it sounded like when a dry leaf gets into the heater blower. 4wd seemed to work fine, and the noise eventually went away, but I still heard it in 2wd, and it got louder as vehicle speed increased. Y'think the noise indicates the pump is getting ready to fail?
'00 Tracker 2-door rust bucket handed down from my sweetie
'00 Tracker 4-door, clean, that she now drives to work