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Engaging 4 Wheel Drive

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by K5XLR8R, Dec 14, 2000.

  1. K5XLR8R

    K5XLR8R 1/2 ton status

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    Is it alright to engage the 4x4 while moving?? if so, is there a specific speed ....whats the proper mode of doing this???
     
  2. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I can throw my 208 into 4HI comfortably up to around 35km/h(around 20 mph). Any faster than that and she protests a bit. I also find that it's easier to engage while I'm moving- she seems a bit sticky if I'm at a stop.

    My truck needs to be in N to engage 4LO. I'm not sure if that's normal, but it works for me!!!!
     
  3. Phyte

    Phyte 1/2 ton status

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    I have an 85 with a 208 and the manual says anywhere below 35mph should be ok. You do have to put the trans in N to shift into 4LO.

    Phyte
     
  4. HarryH3

    HarryH3 1 ton status Author

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    If you have locking hubs and they are locked when you're trying to shift, then you can literally engage them at about any speed. I've shifted mine in to 4WD at 55 mph, just to see if it would work. Not a problem. [​IMG]

    If you have auto hubs, then your transfer case has syncros that will try to spin up the front output shaft to match the speed of the input shaft. It works similar to the syncros in a tranny. Too much speed and you'll quickly wear out the syncros. Some auto lock hubs will stay locked, even in 2WD, until you back up a few feet. With that type of setup you can re-engage 4WD while the hubs are still locked at about any speed.

    With any 4WD system you'll have to nearly stop to engage 4LO.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     
  5. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    you can shift into 4hi while moving but you do have to stop to put it into 4lo at least with mine 3sp with granny low and a np205 t-case and with an auto i do belive it hase to be in nutral to go into 4low

    s.smith 77blazer lookin 4 mud
     
  6. Boss

    Boss 1/2 ton status Author

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  7. Bruiser

    Bruiser 1/2 ton status

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    If your refereing to "shift on the fly" for 4hi and a NP205 then yes. I have been lazy like most people and locked my hubs in as soon as the snow started sticking. You can shift back and forth from 4HI to 2HI while driving. Don't know about doing it at high speed like someone above did. I don't think I want to put that much stress on my drivetrain. OH and I have TH400 and NP205. But you do have to stop and put it in nuetral to get to 4LO and back. Even then I have had to switch to neutral on the tcase then in gear and back to neutral to put it in 2HI without grinding. Have found you can't hesitate, one swift motion or mine tends to protest alittle bit.

    Vincent Michels
    1978 Blazer
    Bruiser (Frost white/Black top/ Light Blue interior)
     
  8. JerzeyJimmy

    JerzeyJimmy Newbie

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    Hey All,

    I know this is going to sound a little rediculous, but I recently purchased an 84 Jimmy, 4 speed on the floor, and I have not yet engaged the 4WD (and no manual came with the truck). I had a friend test ride the vehicle b4 it was purchased and he said all was well, so I'm assuming that the 4WD works. Truth be told, however, I'm a little embarrassed to ask him what the score is with engaging the 4WD. So, since someone has already posed the question, can anyone provide a tutorial for "Idiot's who don't know how to engage 4WD." The do's and dont's, so to speak. Thanks in advance.
     
  9. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    steve i my self have only done this while doing under 10mph more like 5mph so i canot say at higher speeds but i can shift my np205 in 4hi doing 10mph or less with no problems or protesting from the t-case

    s.smith 77blazer lookin 4 mud
     
  10. 90K5

    90K5 1/2 ton status

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    I have a 241 and I thik you can engage it up to either 35 or 55, ut I always do it when I'm going slow. Sometimes I have to put it in N and let it roll a little to get it to lock in

    90K5
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Hey Jerzey,
    Check your sun visor, if you just bought it you may not have flipped the visor down yet. On mine the instuctions for actuating 4WD were printed on the inside of the visor.
    Failing that, you need to verify what kind of hubs you have. Look at your front wheels, in the center of the wheel is the hub, if it has a dial they are manual hubs, no dial and they'll be auto hubs. For manual hubs the first step is to turn the dial to lock on both wheels. If you want hi-range just pull (or push) on the lever into the position marked 4HI. You can be moving when you do this. If you have auto hubs there is no need to do anything but move the lever to 4 HI, again you can be moving when you do this.
    If you want to engage LO-range, again lock in the hubs (or skip this step with auto hubs) put the tranny in nuetral and in one motion move the lever to the 4 LO position. I usually step on the clutch when I do this.
    To go back to 2 WD from 4HI just move the lever back to 2HI, again while you're moving is OK. You can leave your hubs locked, but unless you stop and back up a little the T case may stay engaged.
    To go from 4LO to 2WD stop completely, put the tranny in nuetral and in one motion move the lever to 2 HI. Back up about 10 feet. If you have manual hubs and want to unlock them do it. If you have autos just back up 10 feet or so and forget them.

    The easiest thing to do is find a gravel road and just try it out, as long as you don't shift from Hi range to Lo-range while you're moving you won't hurt anything.

    Rene

    [​IMG]
     
  12. HarryH3

    HarryH3 1 ton status Author

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    Shifting to 4WD at speed with a 205 (or any other part time case) won't put any additional stress on the drivetrain, as long as the front hubs are already locked. Think about it this way, all you're doing when you shift from 2WD to 4WD is engaging the gear to apply power to the front driveshaft. Since the front driveshaft is already spinning at the same speed as the rear one (through the power being transferred through the locked hubs, axle and differential) the gears in the t-case engage quite easily. Try it on a dirt or snowpacked road, you'll be amazed at how easily it shifts into gear, at any speed.

    (If you're one of those folks running something like a 4.10 gear in the back and a 3.08 up front, then DON'T try this since your driveshafts are not spinning at anywhere near the same speed!) [​IMG] Actually, you'll probably just get some gear grinding since the gears won't be able to match up speeds and engage with each other.

    <font color=black>HarryH3 - '75 K5</font color=black>
    http://ThunderTruck.ColoradoK5.com
     

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