1998 GMC 1500 increased pitch whinning during acceleration

Discussion in 'General Chevy & GM Tech Questions' started by maoliverak49, Feb 21, 2013.

  1. maoliverak49

    maoliverak49 New Member

    Here is what's going on! During acceleration from about 5mph, both in 4x4 & 4x2, she makes a whinning noise, from about mid truck, that increases in pitch and volume as speed increases until around 65mph then whinning noise seems to decrease, but still noticable and constant! Noise most intensive @45-55mph range and completely stops when I let off accelerator and coast and returns every time I give it throttle. noise steadily decreases during braking until gone @ approx 5mph. U-joints seems tight/well lubed and no slopp. Does not seem to originate from rear diff at all/fluid level good. T-case level good/no sign metal flake. Tranny surges a bit into reverse when cold/hard shifts reverse from park/drive when warm. shifting good throughout acceleration/deceleration. All 4x4 shifting/performance normal! Need help tracking this most excruciatingly annoying problem down. I'm a home mechanic w most tools/decent trouble shooting skills! Whats next to test/check or should I just spend the hour labor fee and take it to shop to have tech diagnose?
  2. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    I had an '05 Envoy 4x4 with a similar problem.

    I could not feel any problems with the u-joints; the only thing that looked out of place, was one of the joints was rusty (more than the others). When I pulled the driveshaft, the problem was obvious. The u-joint wasn't worn and lose, it was seized and binding.

    On my truck, it was the front joint on the rear shaft.
  3. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    i would start with the u joints, the ujoints are held in place by factory plastic injection. if there is a little plastic frankenstein plug sticking out the sides of the joint then indeed the need to replaced as they are long over due for a 98 4x4. Mine didnt have slop when the time came but you could tell by foot on the brake and shifting form reverse to a forward gear as there was a metal clank sound form the driveshaft immediatly after the gear change. also the plastic injection MUST be torched out as a clamp will not break the plastic, but just bendthe clamp
  4. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    My 03 yukon xl did the same thing. Only made noise on accel. When I let off the gas it would stop. It sounded like it was coming from mid truck or the front end. The sound was traveling under the body. It turned out to be the rear pinion bearing. Most rear end shops will diagnose it for free.
    Last edited: Feb 25, 2013
  5. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Since it seems to be at the mid point of the truck along with checking the U-joints you might also want to check the carrier bearing.
    The carrier bearing shouldnt rattle or move much, these bearings are sometimes harder to diagnose when failing.

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