Humming noise and maintenance

Discussion in 'Trucks and Trailers' started by Barkleymut, May 21, 2001.

  1. Barkleymut

    Barkleymut LawnSite Bronze Member
    Messages: 1,117

    I have a 98 Ram 1500 2WD with an auto. tranny. A couple weeks ago I notice a humming noise that instensifies with speed. Its not tire noise so the only other thing I could think of is the rear differential. I changed the gear oil yesterday and the gears in the back look OK. Anything that I'm missing or is there some maintenance that I am missing? Thanks, Andy. By the way that was the first time I've changed the gear oil and the truck has 50K on it.
  2. 75

    75 LawnSite Senior Member
    Messages: 992

    I don't consider myself to be an expert on these things (especially with trucks from the '90's!) but one question comes to mind - you said the rear gears looked OK, was that strictly a visual inspection or did you turn the driveshaft & see how much "slop" there was in the gears?

    I looked in a GM service manual for light trucks ('77) in the rear axle section, some of the diagnostic info seemed useful:

    It stated that engine/transmission noise can be mistaken for rear axle noise. To test, determine approximate speeds and conditions under which the noise is most pronounced, then stop the truck in a quiet place and leave it in neutral. Run the engine up & down through engine speeds that correspond to vehicle speeds when the noise was most pronounced. If a similar noise is made with the truck standing still, it's likely from the engine/transmission as opposed to the axle.

    Also, driveshaft noises may be mistaken for rear axle noise as well.

    If everything points to the axle as the source of the noise, the manual lists the following as possible causes:

    Faulty propeller shaft, faulty rear wheel bearings, faulty differential or pinion shaft bearings, misalignment between two U-joints, worn differential side gears and pinions, or a mismatched/improperly adjusted/or scored ring & pinion gear set.

    Just quotin' from the book here - hope at least some of the info can help you!
  3. thelawnguy

    thelawnguy LawnSite Silver Member
    Messages: 2,411

    Not to over simplify, but sometimes debris will fall between the cab and the bed and rub the driveshaft, making for odd noises.

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