4WD doesn't engage

BigBody79

BigBody79

Well-Known Member
Joined
Mar 30, 2005
Location
Lumberton
I have a 1998 Silverado Z71 w/ electronic shift t-case

It won't go into 4WD, i've tried just about everything i can. Going forward, going backward, nuetral, 1st gear. It is supposed to shift into 4WD on the fly, but it doesn't. I've had the truck for about 4 months. I've got it to work 1 time, every other time no go.
 
Button console on dash, encoder motor on T-case, encoder position sensor, thermal actuator in front diff (my favorite), wiring issues.

any one of, or combination of these, the actuator in the front diff is the most likely issue, they have been trash since they were first designed, the only thing that got better about them over time was the distinct possibility that that was the root cause.

Easiest way to check for the actuator is to raise truck off the ground,turn ignition on ( do not start engine) engage 4x4, listen while you are waiting at least one minute, then try to spin the front tires, differential action should take place if the actuator is working, if not, opposite wheel will not spin.

While listening you should hear the actuator motor on t-case switching positions. ( at this point EVERY other tech in the shop will also begin using air hammers, ratchets, impacting tools, so you have to listen VERY closely)

Also check fuses, I forget the tag name, but if it goes, you're dead in the water
 
alright, i went out and looked at it a bit. I jacked the front end off of the ground. when i hit the button, nothing happens. the t-case motor doesn't move,nor does the thermal actuator.

i have no idea now.
 
well the thermal stuff id just replace it with a posi lok cable or some sort of home brew device, since it wont pull the collar over the 2 shafts in the diff, cause the thermal stuff is def not cuttin it.
 
alright, if the thermal lock doesn't go, then will the t-case engage? all i hear is a click under the dash and that is pretty much it.
 
Need to look into the cable actuated aftermarket kits they sell to correct this, maybe?
 
i looked for the cable actuated aftermarket kit but i couldn't find one. anybody point me in the right direction?

but would this keep the t-case from shifting?
 
BigBody79 said:
i looked for the cable actuated aftermarket kit but i couldn't find one. anybody point me in the right direction?
but would this keep the t-case from shifting?
Click to expand...

I have seen these on eBay but that would not keep the t-case from shifting into 4wheel
 
Check at the motor on the tcase and see if you get power when you push the 4x4 button or start with the fuse
 
alright

the t-case should shift before the diff right? from what i have read the t-case shifts then the thermal actuator is activiated
 
thats right the diff locks of the vac from the tcase so start with the tcase and go from there
 
Back
Top