whining/humming coming from front end when locked in 4x4

1997 CHEVROLET SILVERADO
155,000 MILES
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CYOUNGBLOOD1980
  • MEMBER
  • 2 POSTS
i have a 97 chevy silverado 4x4, its making a whining/humming noise from front end when locked in 4x4 does it at highway speeds but seems louder when just in town around 35 mph. what could this be?
Nov 19, 2011 at 1:47 PM
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BILLYMAC
  • ✓Experienced Mechanic
  • 2,204 POSTS
This could be low fluid level in the front differential.could be worn pinion bearings or axle bearings.
Nov 19, 2011 at 1:50 PM
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CYOUNGBLOOD1980
  • MEMBER
  • 2 POSTS
thanks! whats should the fulid level be at in the front and how do you check a pinion bearing?
Nov 19, 2011 at 2:45 PM
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BILLYMAC
  • ✓Experienced Mechanic
  • 2,204 POSTS
fill the front diff until it drips out of the fill hole. that is full
Nov 20, 2011 at 2:04 PM
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