What is the proper way to engage 4x4?

[bigblockburb]

I have a 1997 gmc suburban k2500 with the push button 4x4. I put the truck in neutral, push 4 hi, put it in gear and roll forward a bit but the 4x4 doesn’t engage and the light keeps blinking. I replaced the actuator motor and it still does this. It is a NP243C case, 4L80-E transmission.

 

[Nad_Yvalhosert]

The vehicle uses Shift On The Fly engagement.
The transfer case gets engaged, spinning the front driveshaft. Then two halves of the front diff get connected by the actuator.
Coming to a stop, stopping, "put(ting) the truck in neutral, push 4 hi, put it in gear and roll forward a bit but the 4x4 doesn’t engage"? It doesn't work that way.

My '88 has the lever on the floor, same with my '89, push button on my '00. Any of those, I drive any speed above 15 mph, let off the gas pedal, push the button, press the gas pedal again. Click. In 4x4.

Now, the flashing indicator tells me that there's another problem. And you're gonna need some diag time with a wiring schematic and a test light. Start with the t-case position sensor, then test for power at the TLA or worm gear actuator ('97 was a transition year, not sure which you have...)

 

[GoToGuy]

You really should read the owners handbook. Or the factory service manual. A free PDF download if the handbook is available at the " GM Heritage " site, along with other GM materials.
IAEFRTFM

 

[Sean Buick 76]

It’s typical yo have a delay in front cv axles locking into 4x4. I find backing up that using reverse for 5-10 feet after shifting in neutral works best. No matter what you do NEVER use much throttle until both front axles lock in or you can damage parts.

Also if you get stuck off road in 2 wd you really need to be careful to ensure full engagement before going full throttle.

When everything is new things will engage and disengage easier and faster but these are 40 year old trucks.

There is a kit to give instant front axle engagement but it’s been years since I looked into it.

 

[Sean Buick 76]

Regarding the flashing light I’m guessing it’s a push button 4x4. What normally goes on those is the $25 encoder sensor inside the electronic motor that actuates the t case in and out of 4x4. Instead of replacing the $100+ motor you can usually replace the sensor inside. They get fouled up especially from fluid leaks!

Also if you ever get stuck in winter where it won’t shift to 4x4 then disconnect your battery for 5 minutes then shift it right away after reconnecting it. Shift it before the computer pops a code for the t case issue.

Also if your t case is shifting but you don’t get power to the front cv joints then you can use a 1.5” piece of wooden broomstick handle inside the diff actuator To engage it. Then replace the actuator or wiring issue after. I drove a whole winter in 4x4 with the broom stick chunk lol!