94 K3500 dually 4x4 issue

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07-31-2019, 16:57
Jle1208

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!
07-31-2019, 18:06
DmaxMaverick

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.
08-01-2019, 12:20
trbankii

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.
08-02-2019, 12:02
arveetek

Quote:

Originally Posted by trbankii

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
08-02-2019, 14:13
JohnC

Quote:

Originally Posted by arveetek

it's bound to leave me without 4X4 one of these days.

Probably pretty soon, since you made the mistake of posting about it. ;)
08-02-2019, 16:09
trbankii

Quote:

Originally Posted by arveetek

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

Probably pretty soon, since you made the mistake of posting about it. ;)

Exactly! :D
08-05-2019, 05:53
arveetek

Quote:

Originally Posted by JohnC

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! :D

Casey
08-09-2019, 10:06
Robyn

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.....
12-10-2020, 18:20
jggiedeman

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.