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  1. #1

    Default 2500HD Front diff problem

    2002 2500HD 8.1l Allison Trans. In 4wd only, it feels like one side or the other of the front axel is wanting to spin slower than the other. On dry pavement,(yes, I know, don't use 4wd on dry pavement but I just did this to get a feel for what's going on) I can actually hear the tire dragging on the pavement during acceleration. When not accelerating, it is fine. On snow it pulls the truck to one side or the other, then releases sending the truck unexpectedly in the other direction. After this started, I checked the fluid level and it was pretty low. I topped off with 75w90, per the manual. No friction modifier. Would synthetic be better? The truck sits a lot and I thought maybe the clutch pack had siezed up, although I'm not sure it has one. Thanks in advance for the help and for the forum.

    After some more thought, it could also be that one wheel is locked, as it should be and is actually being pushed by the rear wheels because the front propellor shaft is wanting to turn slower than the rear. I don't know what could cause this either though. Anyone have any ideas? Also, why is there an actuator in the front diff? To lock it in 4wd? Doesn't the transfer case handle that?
    Last edited by timmerado; 02-24-2008 at 04:52 PM.

  2. #2


    I'm almost certain GM hasn't put an LS in the front from the factory, so if you haven't put an LS in the front, it's an open diff. No clutches to cause dragging.

    The front wanting to spin faster/slower than the rear could really only be caused by different axle gear ratios front and rear. Any chance that has happened? Only possible if you've had differential work done, and someone put the wrong gear ratio in.

    Tires the same size all around? I've seen such behavior from my BII when I had mismatched tires (all the same "size" but two different manufacturers, which introduced enough difference for the drivetrain to bind up). One tire low on air pressure would have enough difference in size to possibly bind up the drivetrain.

    Any sign of trouble in the CV joints?
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
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  3. #3


    [quote=MrShorty;53733]I'm almost certain GM hasn't put an LS in the front from the factory, so if you haven't put an LS in the front, it's an open diff. No clutches to cause dragging.

    Thanks for the help. I'll check out the possible gearing difference. Don't know the complete history of the truck, but it doesn't seem to have been modified, but worth a check. Tires are the same size, same manufacturer. I've checked the air pressure, but worth a recheck.

  4. #4


    might have a hub issue as well. i agree it most likely is an "Open" diff. have you serviced the wheel bearings and hubs? might be time to inspect and service. look at the diff cover and see if it has RTV or sealent squeezed out if so maybe a gear swap at one time or another..........mike
    Michael Collins
    1993 4X4 Suburban
    many other toys as well

  5. #5


    For anyone interested, I finally gave up and had my favorite mechanics look at this. It wasn't the drive train at all. The front end (steering) was completely worn out!! Replaced lower ball joints, all tie rod ends, pitman and idler arms. I had not even considered this due to the low mileage (33k) on the truck and the mechanics were shocked as well. Are all GMs just a pos like this or did they possibly get some bad parts at the factory? Anyone with any interesting ideas, similar experiences, anecdotes you are welcome to post. Thanks to those who tried to help.

  6. #6


    Ive rarely heard of that happening that early on chevys but I know fords need a change of all that stuff after about 35K most of the time.... I am as shocked as you and your mechanics are but im glad you found your problem
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