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HELP! This sucks - why does it go into FWD???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1986Blazer, Aug 8, 2002.

  1. 1986Blazer

    1986Blazer 1/2 ton status

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    Alright guys.....it happened again today. Since the mechanism inside the NP208 transfer case is not hydrolic, there is not reason for it to shift into gear. There must be some kind of mehcanical input to cause it to do this.

    I am wondering, could I have a bad HUB that engages one or more of the front axles? This would then engage the differential and thereby turn the front driveshaft. I am fairly positive the front drive shaft can turn and the gear inside the transfercase would only spin. It would not be engaged with anyother gears.

    The terrible sound that is made if the front driveshaft rubbing against the exhaust crossover. That is something I need to fix. But there is NO grinding like you would expect with the front ration being 3.08 and the rear being 4.56.

    Any thoughts......Bad HUB???????

    Chris
     
  2. Blue85

    Blue85 Troll Premium Member

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    What's happening?
     
  3. Sandman

    Sandman 3/4 ton status Author

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    I had a similar problem when I striped the splines away on a front driveshaft. The fluid sloshing around in the transfer case was enough to rotate the front driveline. Since the splines were toast, it made an ungodly grinding noise. I ended up tying it up so that it couldn’t rotate at all until I was able to fix it. I am guessing that this is what you are seeing.
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Do you have auto hubs?

    Rene
     
  5. Blue85

    Blue85 Troll Premium Member

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    Auto or Manual hubs?

    Why would a hub engage and then disengage with no input? Maybe there is too much grease in them? A bad spring? Perhaps your shift forks are worn in the transfer case, letting it slip into 4WD?

    How about this: remove the front driveshaft and but chalk marks on the pinion yoke and the T-case front ouput yoke. Whichever one moves is the end the problem is coming from.
     
  6. Pure Insanity

    Pure Insanity 1/2 ton status

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    If you dropped your case when you lifted it did you adjust the linkage? What may be happening is when the motor torques and twists, it is making the case engage by pulling on the linkage just enough to pop it in. Just a thought, but try disconnecting the linkage and ride around for a while and see if it kicks in. You dont have matching gears so you wont be engageing it anyhow.
     
  7. 95 Silverado

    95 Silverado 1/2 ton status

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    I agree, check the linkage. turning the front axles with the transfer disengaged shouldn't make any noises, if the linkage is causing the transfer case to try to engage with the drive shaft not turning it will grind, is this the noise you are hearing? Put it in 2WD, disconnect the transfer case shift lnkage and drive it, if it stops doing it , that's your problem.
     
  8. 1986Blazer

    1986Blazer 1/2 ton status

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    Rene:

    I have auto hubs.

    Everyone else, thanks for the input. Here is what I know:

    1. I did not do anyting to the TC during the lift and the shifter does not change position at all when it happens.
    2. When it does happen, I need to reverse it to get it to stop and sometimes I need to reverse it a few times before it disegages.
    3. The grinding is from the FT driveshaft scraping against the exhaust crossover from the pass. side to the drivers side. There are significant grind marks on the ft driveshaft where it contacts the exhaust pipe.
    4. The front axle does not seem to be fully engaged since the truck still seems to go forward fine, there is no jumping or skipping like I'd expect.

    Here are some questions I do not know:

    1. If you lifted and supported the truck on jack stands and removed the FT driveshaft from the FT axle, can you then turn the driveshaft by hand. If so, then the front HUBS could engage and thereby cause the driveshaft to turn but not necessarily engage any gears in the TC. Anybody know about this.
    2. Could damages springs in the autohubs really cause the hubs to grab ahold of the axles?
    3. What is the fastest and least expensive for premium Warn Hubs.

    I need some answers fast so I can get this thing going finally.

    Oh, yea....is there really any problems with running without the FT driveshaft??

    Chris
     
  9. Sandman

    Sandman 3/4 ton status Author

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    Maybe try these guys for your hubs.

    www.4wheelparts.com

    You can take the front shaft off with no ill effects. Mine is off untill my new yoke shows up. Broke it on a rock.
     
  10. Blue85

    Blue85 Troll Premium Member

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    Ah, auto hubs. They may be going bad. Sometimes they start to hang up even when the front axle hasn't turned to engage them. That would explain why you have to back up to make it stop. This is my first guess for your problem.

    It's also possible that the T-case has worn shift forks or needs linkage adjustment. That could let it just barely try to engage 4WD enough to turn the front driveshaft a little and engage your hubs.

    It is fine to run without the front driveshaft. You have no need for it anyway, since your front and rear gears don't match. However, if the problem is really the hubs engaging, you will spin your front spider gears (at least one of them, anyway) continually and they are not really designed for this. They just have thrust washers behind them.

    If you want to troubleshoot the hubs real quick, you can remove them and tape plastic bags over the hub openings to go for a test drive. Or just by the manuals and swap them in. I always say that it's fine to run auto hubs, but you should have a set of manuals stored in the truck for the day you blow an auto.
     
  11. Emmettology 101

    Emmettology 101 3/4 ton status

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    My front shaft spins when goign down the road and the tcase being in 2wd and the hubs unlocked. That is a trait of the 208's. If you leave the vehicle in drive on a hill and get out and check the shaft(I would advise you to have someone in the vehicle with their foot on the brake), it will spin freely. It is like someone else said and the fluid or something in the case makes the shaft spin.
     
  12. 1986Blazer

    1986Blazer 1/2 ton status

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    I am going to disengage the front driveshaft for now. I need to get the exhaust redone and since the gears are different, I can't go into 4X4.

    I will also purchase the manual WARN hubs - permium ones I expect. As far as the TC functioning properly, I need to check it out.

    Thanks for all the input and if anyone has any other info, please let me know.
     
  13. Pure Insanity

    Pure Insanity 1/2 ton status

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    Well give us a follow up Chris when you get it done. Kinda curious as to what you find. /forums/images/icons/wink.gif
     
  14. m j

    m j 1/2 ton status

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    any TC will do that
     
  15. BLUESMAN

    BLUESMAN 1/2 ton status

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    Maybe I'm missing something,but are you running a front driveshaft?You atated you have 3.08's in the front and 4.56's in the rear?I'd remove that front shaft in a hurry,otherwise you will explode that t case.Maybe this is your major problem!Mike
     
  16. Emmettology 101

    Emmettology 101 3/4 ton status

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    My friend has a 78 with a 205 and his shaft doesn't spin going down the road....
     

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