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Thread: 94 K3500 dually 4x4 issue

  1. #1
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    Ohio
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    Default 94 K3500 dually 4x4 issue

    I have a 1994 Chevy 3500 6.5L. When I bought the truck the front drive shaft was out of it. I put the drive shaft back in and when you put it in 4x4 the drive shafts both turn. However, the front wheels don’t lock.

    I have checked all over, found a vacuum hose I’m assuming. It hooks right above a plug on the transfer case. I followed it up past the transmission and it was zip tied to a bolt hole. I’m assuming it has another piece that is supposed to attach to it and go someplace. I have no clue where this hose would go too. Or if anyone has some detailed information on what could possibly be wrong.

    Any help would be great!

  2. #2
    Join Date
    Apr 2001
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    CA
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    13,572

    Arrow

    The hose is a thermal expansion vent. It's supposed to go nowhere (above fording level), but there should be a vented cap on the end.

    The problem with the front diff locker is probably the actuator. Could also be the harness, or the switch at the TC. For 1994, it was a thermal actuator. Later models use a stepper motor. You can either upgrade to the latter (not plug 'n play), or repair the former. I recall detailed article(s) for all of the above at www.thedieselpage.com. Contact More Power if you can't find it/them.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    Mar 2000
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    Default

    The other option is the Posi-Lock: http://4x4posi-lok.com/app_chevy-k.html

    Changes the thermal actuator to a mechanical setup. It's on my list for both my trucks this Fall when I have some time.
    '94 GMC 6.5TD K1500 4L80E 2-Door Yukon SLE 221K
    '93 Chevrolet 6.5TD K2500HD NV4500 Std. Cab Longbed 187K
    '85 Toyota 22R RN60 4x4 Std. Cab Shortbed 178K (Currently retired for rebuild)
    Diesel Page Member #2423

  4. #4
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    Oct 2001
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    Default

    Quote Originally Posted by trbankii View Post
    The other option is the Posi-Lock: http://4x4posi-lok.com/app_chevy-k.html

    Changes the thermal actuator to a mechanical setup. It's on my list for both my trucks this Fall when I have some time.
    This has been my plan for quite some time as well. Just haven't gotten to it yet. Thankfully, I've never had a problem with my actuator in the 14 years I've owned the Tahoe.... knock on wood... but it's bound to leave me without 4X4 one of these days.

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  5. #5
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    New Hampshire - Live Free or Die
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    Default

    Quote Originally Posted by arveetek View Post
    it's bound to leave me without 4X4 one of these days.
    Probably pretty soon, since you made the mistake of posting about it.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  6. #6
    Join Date
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    Default

    Quote Originally Posted by arveetek View Post
    This has been my plan for quite some time as well. Just haven't gotten to it yet. Thankfully, I've never had a problem with my actuator in the 14 years I've owned the Tahoe.... knock on wood... but it's bound to leave me without 4X4 one of these days.

    Casey
    It's been on my list for some time as well. I've never had it not engage eventually, but there have been a number of times that it was stubborn and had me wishing I had already done the conversion.

    Quote Originally Posted by JohnC View Post
    Probably pretty soon, since you made the mistake of posting about it.
    Exactly!
    '94 GMC 6.5TD K1500 4L80E 2-Door Yukon SLE 221K
    '93 Chevrolet 6.5TD K2500HD NV4500 Std. Cab Longbed 187K
    '85 Toyota 22R RN60 4x4 Std. Cab Shortbed 178K (Currently retired for rebuild)
    Diesel Page Member #2423

  7. #7
    Join Date
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    Default

    Quote Originally Posted by JohnC View Post
    Probably pretty soon, since you made the mistake of posting about it.
    LOL! Yup... how dumb of me! Better order that Posi-Lok right away!

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  8. #8
    Join Date
    Apr 2001
    Location
    Newberg Oregon
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    12,282

    Default

    Most common failure is the Thermal actuator.

    Easy fix..

    Unplug the actuator off the front diffy on the RH side of the diffy.

    Unscrew the old unit and replace it.

    Make sure to fasten the wires back securely or THEY WILL GET TORN OFF.....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  9. #9
    Join Date
    Dec 2000
    Location
    Walla Walla WA
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    Default

    There is a metal plug that has to be inserted also. This ensures it meets the length of the original unit. Everything would indicate that the unit works but still not engage the front diff. You would just need to unscrew the electrical unit and verify. This is only for an upgraded control unit, not the original thermal heated unit.
    1994 K2500 ext cab. Recently repowered with; Non-cracked 599 block, factory compression, used old DSG girdle for main caps. Factory for what remains. Changed diffs to 3.42. Fuel economy Hwy 22.5 mpg US, in town without lcokup in 2nd/3rd - 18 mpg US.
    1994 K3500 CC LB Silverado. Next project. Built for endurance, power and gearing. Plan on opened up intake and exhaust sytem, best cooling mods, 4.11 gearing 4L80E, followed by Gear Vendors OD. Need to be able to split all gears and have lockup in 2nd/3rd/4th. Tan interior cloth, Bad ass dark blue (coming) aluminum wheels and air ride (coming)

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