97 4WD actuator upgrade

[Gary Williams]

My Z71 doesn't seem to want to go into 4WD all of a sudden. I haven't had a chance to troubleshoot yet, but if it is the actuator, what is this upgrade I have seen some talk about on here. Thanks.

[Jeremy-WI]

The upgrade is to the 98 style electric actuator, the previous years used a problematic thermal actuator. You need an electric actuator and a wiring harness adapter to complete the project, the GM harness adapter includes a spacer that is needed for the electric actuator to engage the axle.

[Gary Williams]

I have a thermal actuator? It uses heat? Hmm. So are the electric upgrade parts available at, say, O'Rielly's? Is this a difficult upgrade or should I just replace with the original type actuator?

I'll add that it has been in the 100's here in Texas lately. Does that affect the thermal switch?

[Jeremy-WI]

I believe the thermal unit heats up oil and as the oil expands it pushes a cylinder out to engage the front axle.

You may want to contact someone at gmpartsdirect.com and ask them if part number 12376319($141 plus shipping) will work on your vehicle to convert to the newer actuator- the part numbers I have are different but I think this might be a kit where you get the new actuator, wiring harness adapter and the spacer in one box. Actually check to make sure yours isn't already converted. The actuator is on the passenger side of the front axle, look for the wires and you should find it, if yours is metal then its thermal, the updated ones are plastic and stick out about 4-6 inches.

If you go to autozone.com and enter your vehicle info and search for axle actuator you will be able to see pictures of the thermal(AZ part SW2084) and the updated actuator is AZ part SW2085.

Another benefit of the upgrade is that if you shut your truck off in 4x4 the actuator will stay engaged instead of releasing the front axle
The one bad part of the upgrade is that you have a wire to splice into to power the actuator, it adds a brown wire to the actuator that needs power whenever the ignition switch is on. I found a brown wire sticking out of the wiring harness between the underhood fuse box and firewall that worked great

[Gary Williams]

Thanks, Jeremy. My son works at the GMC dealership, so I'll have him look up the part.

[Gary Williams]

After doing some research on the internets, it looks like a pretty easy upgrade except where does that really long brown wire splice in. Behind the dash where the switch is? My truck still has the old thermal type.

[Jeremy-WI]

Gm recomends that it be spliced into a brown wire at the transfer case switch which can be a pain to get to. On my truck I spliced into a brown wire between the underhood fuse center and firewall that is on the same circuit as the brown wire at the transfer case switch