89 gmc 1500 4wd problems

[Newtothisgame]

my 89 sierra when engaged in 4 wd the indicator light comes on showing that it is in 4 wd then when i press gas or shift the light goes out then back on so im not getting power to the wheels and it worked fine last year is there a sensor or whats going out need help fast 2wd kinda sucks in winter
Thanks James

 

[02XLT4X4]

GM had the fairly odd idea of having a heated oil actuator for the front axle that engaged it for 4wd, they are fairly common to fail. Aside from that I couldn't tell you the exact way to test them.

 

[Anonymous-0]

Could be that the actuator in the front axle is not engaging fully - common problem on these.

 

[bradk]

Actuator in front diff is pro'ly getting weak.Works by warming up a gas inside the actuator and expansion pushes the gears together to mesh.

An update kit using a motor drive is available from GM to eliminate the old slow actuator.

Another thing I've seen is the gears may have burrs at the ends not allowing full engagement due to a weak actuator.Once diassembled,can be cleaned up w/file.