Question about Chevrolet Suburban 2500

2 Answers

Not shifting 2wd/4wd correctly

I have a 1996, 2500, 6.5 ltr. 4wd, turbo deisel Suburban. It is making a noise from the mid-cabin as if two gears were making near contact. It is a metal on metal sound when it is under power and only when in two wheel drive, especially if under torque (like running up hill). If we put it in 4 wheel, it seems to stop. There looks to be some sort of transfer case that is in the area where the noise seems to be coming from. Does anyone know about what could be the cause? I feel as though it is a celenoid issue where it is not shifting in and out of 2wd and 4wd completely. Any help on this?

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  • scott_oppat Jul 19, 2010

    Hello,

    I am not sure if you can read the previous advice given, but it is hard to follow as the editing is poor. Can you review and rewrite in a way that maybe makes more sense? Since the noice seems to be coming from the case near the mid-chassis, I am guessing it has something to do with engaging in or out of 2 and 4 wheel drive. Thanks1

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Hi

Most probably wheel bearings or it might be the axle if it is front wheel drive.

Let us know if you have something more to know else accept the suggestion.
Thank You for contacting Fixya.com

Posted on Jul 19, 2010

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The transfer case needs to be removed and checked.
Remove the transfer case and check it.internally. The procedure to remove the transfer case is as follows:-- crawl under the truck you will see the bolt pattern facing the front of the truck should be 15mm and they will be in a circle pattern between the transmission and transfer case .that is where you remove it.You will have to take the things off as to remove the transfer case. --- In some cases its noticed that transfer case motor gets faulty. In this system the transfer case motor must engage first, then a signal is sent to engage the front differential motor to engage the differential.  I think the problem is one of two items, either the front differential engagement motor is in-op or the transfer case motor is malfunctioning and sending false signals to the VCM (vehicle control module). If the front axle for any reason does not allow the front propeller shaft to spin while in the 2WD setting, the clutch pack in the transfer case will overheat because of the speed difference (slip) across the clutch pack between the stationary front driveshaft and the rotating rear driveshaft. the front axle, the transfer case should also be inspected for overheating by inspecting for burned fluid or a free rotating front driveshaft. In addition to correcting front axle concerns, necessary repairs should be made to the transfer case.  The auto locking hubs are not engaging properly and will need to be removed and spline sets checked for broken teeth on locking hub and locking shaft. Also check that the engaging spring inside the hub has enough tension to engage the hubs they may be broken. If the hub are all ok then you have a problem in the transfer box, where the 4WD lever is not meshing the transfer box properly. POSSIBLE THE ACTUATOR ON THE FRONT AXLE IS BAD ? YOU NEED TO SEE IF THE FRONT DRIVE SHAFT IS ROTATING WHEN THE 4 HI IS ENGAGED WITH OUT RUNNING YOUR SELF OVER IN THE PROCESS. 
 
THERE IS AN ACTUATOR ON THE FRONT AXLE AN ONE ON THE TRANSFER CASE, THE ONE ON THE TRANSFER CASE LOCKS THE DRIVE SHAFT IN AND OUT OF 4 HI & 4 LOW. THE ACTUATOR ON THE FRONT AXLE LOCKS THE FRONT DRIVE SHAFT IN.
 

Thanks. Keep updated for any more query. You can rate this solution and show your appreciation.

Posted on Jul 18, 2010

  • raj somaiya
    raj somaiya Jul 19, 2010



    1994-1998 Chevrolet Chevy Suburban - 4WD:--


    Slips in 4-Wheel Drive, Noise, Vibration, Leaks, Hot Odor (Diagnose and Repair Front
    Differential and/or Transfer Case) #02-04-21-005A.



    Condition


    Some customers may
    comment on any of the following conditions:



    Slips in 4wd


    Noise


    Hot odors


    Leaks


    vibration


    Cause


    The front axle may
    have excessive preload in the pinion or carrier bearings or may be locked up
    not allowing the pinion to rotate freely. Vehicles with a NVG 236 or 246
    transfer case (RPO NP8) have a preload in the clutch pack of the transfer case
    that supplies torque to the front driveshaft at all times. The front and rear
    driveshafts should be rotating at approximately the same speed (the front
    driveshaft display on the Tech 2® may be slightly higher but never less than
    the rear).



    Diagnostic Tips


    Position the vehicle on the hoist and raise
    the hoist until all four wheels are off the ground.



    Connect the Tech 2® to the vehicle.


    Start the engine.


    Select 2 HI with the transfer case selector
    switch.



    Apply the service brake and move the
    transmission selector lever in any forward gear.



    Release the service brake.


    Observe the front and rear propeller shaft
    speeds displayed on the Tech 2®. The



    front and rear driveshafts should be rotating
    at approximately the same speed (the front driveshaft display on the Tech 2®
    may be slightly higher but never less than the rear). If they are not, skip to
    the Correction section below. If the driveshaft speeds are approximately the
    same, diagnose for other conditions that may be causing the concern. If the
    vehicle is stationary, the front propeller shaft should not rotate freely. It
    may take up to 54 N·m (40 lb ft) of torque to turn the front output shaft of
    the transfer case. If the front axle for any reason does not allow the front
    propeller shaft to spin while in the 2WD setting, the clutch pack in the
    transfer case will overheat because of the speed difference (slip) across the
    clutch pack between the stationary front driveshaft and the rotating rear
    driveshaft.



    correction


    For vehicles with the NP8 transfer case
    option (Autotrak with push-button selections for 2HI. Auto 4WD, 4HI, 4LO and
    Neutral) only, when a vehicle comes in for issues with the front axle, the
    transfer case should also be inspected for overheating by inspecting for burned
    fluid or a free rotating front driveshaft. In addition to correcting front axle
    concerns, necessary repairs should be made to the transfer case.






  • scott_oppat Jul 19, 2010

    Thank you for your response. If it is either of the "engagement motors" you describe, any idea as to the cost of fixing either of the engagement motors? Not sure if you folks on this service give some repair price estimates.



    Thanks!

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