98 gmc sierra 3500 4wd won't engage - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cumminsbayou · 12-21-2013, 01:00 AM

I have a 98 gmc 3500 and the 4wd won't engage in it. The 4wd stopped working about a few weeks ago when it first started to get cold around me. I crawled under the truck and i know the transfer case is engaging, and i also know that no fuses have blowed in the fuse box. I've did some research and I found that the 4wd actuator is a common problem with some of these trucks so today i stopped by the parts house and got one and swapped it out in a parking lot up the street because i was planning on taking it offloading today and the 4wd work…..WRONG lol. I ended up going any was lol. I did some more research on them when i got back and i've come to the conclusion that i just want to bypass it and leave it engaged some how all the time. I found a post somewhere from years back about a guy that did it on his truck. I realize there may be some concerns here with it being engaged all the time but i'm not worried about it.
here is the link- http://www.fullsizechevy.com/forum/g...ld-thread.html

If you scroll all the way down someone says you can do this by putting a 14mm socket on the actuator, I'm wondering is this true? And has any one else built there on 4wd actuator like this?

Here the truck is its self if any one is wondering

LynnJr · 12-22-2013, 05:19 PM

The actuator itself is just an electric ram.When you engage it it grows longer in length and pushes against a plate that locks up the front end.
I have not tried a 14mm socket but it probably works just fine.
I bought a large bolt and welded some ears on it after grinding down the hex head.It looks like a very large wingnut.
I really need to post pictures as it is dirt simple to make but sounds hard.

83GMCK2500 · 12-26-2013, 04:19 AM

The actuator for the front differential was upgraded at some point by GM. The earlier designs are referred to as thermal linear actuators as there is a plastic/wax material in them that has to warm up before the actuator engages. It was not the greatest design just in general, that whole heat cycling thing and susceptibility to temperature fluctuation/moisture/etc. The revised actuator (the only one available from GM) is fully electric, no delay, no waiting. When it gets the signal it pops.

Otherwise there is a 4x4 posi-lok (purposely misspelled), replacement that is a cable operated actuator that is offered.

83GMCK2500 · 01-05-2014, 02:44 PM

Update on this? Had a chance to work on it?

12-21-2013, 01:00 AM	#1
cumminsbayou Registered User Join Date: May 2013 Location: fairhope Alabama Posts: 2	98 gmc sierra 3500 4wd won't engage I have a 98 gmc 3500 and the 4wd won't engage in it. The 4wd stopped working about a few weeks ago when it first started to get cold around me. I crawled under the truck and i know the transfer case is engaging, and i also know that no fuses have blowed in the fuse box. I've did some research and I found that the 4wd actuator is a common problem with some of these trucks so today i stopped by the parts house and got one and swapped it out in a parking lot up the street because i was planning on taking it offloading today and the 4wd work…..WRONG lol. I ended up going any was lol. I did some more research on them when i got back and i've come to the conclusion that i just want to bypass it and leave it engaged some how all the time. I found a post somewhere from years back about a guy that did it on his truck. I realize there may be some concerns here with it being engaged all the time but i'm not worried about it. here is the link- http://www.fullsizechevy.com/forum/g...ld-thread.html If you scroll all the way down someone says you can do this by putting a 14mm socket on the actuator, I'm wondering is this true? And has any one else built there on 4wd actuator like this? Here the truck is its self if any one is wondering __________________ 98 sierra 3500 crew cab long bed single rear wheal 454 z71 86 chevy c10 silvered edition short bed 305 01 chevy silverodo 1500 z71 327 vortec

12-22-2013, 05:19 PM	#2
LynnJr Registered User Join Date: Nov 2012 Location: santa rosa,california Posts: 650	Re: 98 gmc sierra 3500 4wd won't engage The actuator itself is just an electric ram.When you engage it it grows longer in length and pushes against a plate that locks up the front end. I have not tried a 14mm socket but it probably works just fine. I bought a large bolt and welded some ears on it after grinding down the hex head.It looks like a very large wingnut. I really need to post pictures as it is dirt simple to make but sounds hard.

12-26-2013, 04:19 AM	#3
83GMCK2500 Registered User Join Date: Sep 2009 Location: Beaverton, OR from WA State Posts: 1,515	Re: 98 gmc sierra 3500 4wd won't engage The actuator for the front differential was upgraded at some point by GM. The earlier designs are referred to as thermal linear actuators as there is a plastic/wax material in them that has to warm up before the actuator engages. It was not the greatest design just in general, that whole heat cycling thing and susceptibility to temperature fluctuation/moisture/etc. The revised actuator (the only one available from GM) is fully electric, no delay, no waiting. When it gets the signal it pops. Otherwise there is a 4x4 posi-lok (purposely misspelled), replacement that is a cable operated actuator that is offered. __________________ Devin 1983 GMC High Sierra 2500, 4x4, RC/LB, 400 S.B., SM-465, NP-208, Corporate 10 bolt & 9.5" 14 bolt 1996 GMC Sierra SLE 3500 DRW, 4x4, EC/LB, Vortec 454, NV-4500, BW-4401, AAM 925 & AAM 1050 1997 GMC Sierra SLT 1500 4x4, Z71/F44, EC/SB, Vortec 350 My Introduction with my '83s History New Daily, the '96

01-05-2014, 02:44 PM	#4
83GMCK2500 Registered User Join Date: Sep 2009 Location: Beaverton, OR from WA State Posts: 1,515	Re: 98 gmc sierra 3500 4wd won't engage Update on this? Had a chance to work on it? __________________ Devin 1983 GMC High Sierra 2500, 4x4, RC/LB, 400 S.B., SM-465, NP-208, Corporate 10 bolt & 9.5" 14 bolt 1996 GMC Sierra SLE 3500 DRW, 4x4, EC/LB, Vortec 454, NV-4500, BW-4401, AAM 925 & AAM 1050 1997 GMC Sierra SLT 1500 4x4, Z71/F44, EC/SB, Vortec 350 My Introduction with my '83s History New Daily, the '96



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