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Trans Problem 99 GMC Sierra 2500

Discussion in 'Truck & Equipment Repair' started by ACL&L Plowing, Dec 4, 2005.

  1. ACL&L Plowing

    ACL&L Plowing Junior Member
    Messages: 29

    One of my guys made the mistake of shifting the trans into 4wd while the truck was moving and in Drive. Now the front end is vibrating when traveling about 25 mph or more, sounds like something is grinding. It is OK when truck is switched out of 4 wd into 2 wd. What could this be? It is a 99 GMC 2500 Sierra. What might it cost?
  2. lorentzlawnsnow

    lorentzlawnsnow Senior Member
    Messages: 143

    sounds like it could be a u-joint. lock it in 4wd and get under it and wiggle the front drive shaft. if it wiggles you need a u-joint
  3. Mowerpan

    Mowerpan Senior Member
    Messages: 305

    Arent you supposed to be able to shift it into 4wd while its in drive? I know on my 93 s-10 you can put it in 4wd when your moving, your allowed to do that. Maybe you just didn't notice the problem before as you didn't drive that fast in 4wd?
  4. lorentzlawnsnow

    lorentzlawnsnow Senior Member
    Messages: 143

    you should be able to shift into 4hi while driving. 4lo you can not.
  5. Jpocket

    Jpocket Senior Member
    Messages: 302

    I always stop and put it in nuetral real quick, eventhouth the new truck has electronic 4wd
  6. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    Gm has had shift on the fly forever. I don't think you could possibly get it into 4 low while moving. I wonder what the guy actually did to damage it...
  7. Mowerpan

    Mowerpan Senior Member
    Messages: 305

    What ^ said. It won't let you put it in 4lo and it has shift on the fly like I said above, so either back ujoints or something else went unnoticed earlier or your guy fed up your truck. Get it checked out.