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Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 17157
Experience:  GCM master tech over 25 years
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96 GMC Sanoma 4wd wont disengage. pushed lever on floor all

Customer Question

96 GMC Sanoma 4wd wont disengage. pushed lever on floor for 4wd all the way forward all lites go out, but as I travel down the hwy sounds like still engaged as their is a loud whining coming from transfer case ,I know Im not suppose to travel more than 35 - 40 MPH in 4wd but the faster I go the louder it gets.Have moved 4wd lever back and forth in and out of 4wd numerous times makes no difference? Can you help ?
Submitted: 2 years ago.
Category: GMC
Expert:  Gary replied 2 years ago.

I am very sorry for the long wait

the most common issue that will cause a noise like this is usually the front axle staying engaged or partially engaged when the transfer case is in 2HI

to eliminate this being the problem as seen here in this picture is a 3 vacuum hose connector connected to the drivers side topish of the transfer case connected to the vacuum ball switch

can you unplug that 3 vacuum hose connector and plug off the 3 hoses with something and drive it and see if it still does this ?

Customer: replied 2 years ago.
Ok thank you im going out to try that right now as I have vehicle up on ramps and can get right at it . Ill let you know soon,TOM
Expert:  Gary replied 2 years ago.

ok Tom let me know

if the noise goes away replace that vacuum ball switch in the transfer case that the 3 vacuum lines connect too

if it still makes this noise be SURE the floor shifter is actually shifted into 2HI at the case and not in between gears or partially in 4WD at all

Expert:  Gary replied 2 years ago.

Tom how are you making out ?