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1982-2000 C/K Truck & SUV Chassis & Drivetrain Discussion Forum for the 1982-2000 GM Pickup Trucks and SUVs, and their Transmissions & Drivetrains, cab, chassis, electrical systems and a lot more.

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  #1  
Old 07-31-2019, 04:57 PM
Jle1208 Jle1208 is offline
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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!
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Old 07-31-2019, 06:06 PM
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DmaxMaverick DmaxMaverick is offline
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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.
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  #3  
Old 08-01-2019, 12:20 PM
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trbankii trbankii is offline
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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.
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Old 08-02-2019, 12:02 PM
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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
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Old 08-02-2019, 02:13 PM
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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.
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Old 08-02-2019, 04:09 PM
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trbankii trbankii is offline
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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!
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  #7  
Old 08-05-2019, 05:53 AM
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arveetek arveetek is offline
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Quote:
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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
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1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's; Kennedy OPS harness, gauges, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box; dual t/stats, HO water pump, Champion radiator; Racor fuel filter; 352K miles and running strong!
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Old 08-09-2019, 10:06 AM
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Robyn Robyn is offline
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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.....
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