4X4 problems... all the usual fixes arent working

I have a 1999 GMC SONOMA SLE 4X4. The 4X4 will not work. I have tried all of the usual fixes, vaccum lines, switch, unhook the battery, relays, all of that and nothing works. When I push the button for 4x4 HI there is a "klunk" underneath the vehicle and if left at idle all four wheels move, but as soon as I give it some throttle then only the rear wheels move. The same with 4x4 LO, I put the vehicle into N then engage the 4x4 lo, there is a "klunk" like it is engaging and it works for about 3 seconds and as soon as I give it throttle it stops. This is annoying the hell outta me since I bought the vehicle for the 4x4. Any help would be great.

Did you check the vac actuator under the battery for holes or tears? If that's ok, it's more than likely the encoder motor isn't engaging fully and will have to be replaced.

while driving in 2 wheel do you get a grinding noise coming from the front end?

What 'stops', after you give it throttle???

What 'stops', after you give it throttle???

Wow, what a way to ressurect a dead thread! :icon16:

My 97 Sonoma Does The Same But The T/c Is Engaged But The Front Wheels Dont Spin

My 97 Sonoma Does The Same But The T/c Is Engaged But The Front Wheels Dont Spin

Check the vac actuator under the battery.

It's probably your front hubs.

thread is now almost 3 years old. please refrain from posting in old threads :nono: