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Shifting Tcase

Discussion in 'The Garage' started by CHEVY 4WD, Jan 20, 2003.

  1. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    would it hurt anything to shift from 4L into 4H if you were racing on the street(in like a Jeep or similar)? I sal a guy shift from 2wd to 4wd at the sled pull make me wonder it dident grind or anything and he dident let of the gas.
     
  2. u2slow

    u2slow 1/2 ton status

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    Yes. 4LO to 4HI shifting while moving is the leading cause of planetary t-case failure.

    One you have a NP208 or NP241 apart, it becomes very obvious why this is so. There is a collar that engages a ring with some very small teeth on it. There is no synchro rings that I'm aware of... just the teeth are pointed to aid in the two sliding together. These small teeth become shredded on hi/lo shifts while driving.
     
  3. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    I dident think it would be a good idea but just wondering
    what if you hit neutral then shifted to hi then back in drive? BTW 2hi into 4hi dosent hurt anything?
     
  4. u2slow

    u2slow 1/2 ton status

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    Shifting to neutral won't make any difference. You're still trying to mesh a faster moving part with a slower moving part, one turning 2.7 times faster than the other.

    The input side of the t-case won't begin to spin down until the t-case is in neutral. Even then, you'll be shifting a collar (moving according to the speed of the rolling truck) to mesh with a now stationary input side.

    2wd to 4hi and 4hi to 2wd is okay since the front output and driveshaft are already turning at the same speed of the truck. The t-case uses a synchro to enagage the front output drive so that its brought up to speed as its shifted (basically, lets you use auto-hubs).
     
  5. txbartman

    txbartman 1/2 ton status

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    On my 208, I can't go from 4hi to 4lo without having the tranny in neutral first. And from my racing days, I don't see the point of this in the first place. I can't think of many instances where you would be in 4lo on the street. And especially not while racing. And if you're on the street, why use 4wd anyway? You probably don't need the added traction as much as you need the engine power.
     
  6. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    well it would have been with the hubs unlocked and some 4 bangers are kinnda slow and if you could use a lower gear it would come out of the hole faster. its not for a blazer
     
  7. 87sm465np208

    87sm465np208 1/2 ton status

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    toyota made a T-case that could be shifted into 4LO on the fly, why i dont know but they did. and remember when you shift into 4 lo and you hear it grind, thats just metal leaving /forums/images/graemlins/blush.gif.

    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/truck.gif
     

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