When i push the button to put it in fourwheel drive. the hubs do not engage.

Did you reverse more than 10 metres? Sounds like the hubs are locked into 4wd.this will work if you have auto hubs.but sometimes you have to turn the hub manually if they don't disengage.if you have gone some time or distance in 4wd

IS IT THE 4X4 SHIFT ON THE FLOOR YOU PUSH THE BUTTON IN ON TOP OF THE SHIFTER AND ENGAGE YOUR 4 WHEEL DRIVE I NEED TO KNOW SO I CAN HELP HERE AND IT LIGHTS UP THE AX;E YOU HAVE ENGAGE POHLCAT

This depends on what system you have installed in your truck. If you have push button 4x4 with auto locking hubs then you would put your vehicle in neutral and press the 4x4 button. You then drive froward about 10 feet and the auto locking hubs should then be engaged.

If you do not have push button control and you have a gear shifter which controls the transfer case you would push the level in 4x4 hi or low depending on what you want (while in neutral) then drive forward about ten feet so the hubs lock. If you have manual locking hubs you need to manually engage the hubs before you put it in 4x4 mode,

There is a TSB for replacing the IWE ( Integrated Wheel Ends ) solenoid, as the 1st design can ingest water and introduce it to the IWEs, causing low vacuum, and the gears for the IWE are grinding.

http://my.voyager.net/~sscully/file_tsb06_08_15.pdf

To cure this until you get the new IWE solenoid ordered and installed, pull the vacuum lines from the IWEs and plug them. This will leave the IWE gears engaged, so they are not trying round off the teeth.

There are 2 lines to the IWE, 1 is the vacuum line, the other is a vent line, that routes into the engine compartment, with an open end, make sure you pull and plug the correct line.

This will have the front hubs engaged to a dead axle, so it will decrease mpg, and you will feel a bit of loss of power, but better than ruining a set of IWEs that will cost ~500.00 to replace.

On an 86 you probably still had the hub locks on the outside. You have to get down off the truck and manually turn the hubs to the lock position. The hubs are located in the middle of the wheel. Then Put the 4 wheel drive gear shift to 4 hi or 4 low. At the low level it runs very slowly and very low geared. At 4 hi, it runs normal but the 4 wheel drive engages. When you are not using the 4 wheel drive it is good that you get off the truck and turn the hubs counter clockwise to the off position.

check fuses should b a 4wd fuse refrence your owners manual. if not problem try removing batt connectors pos and neg. resetting computer. sometimes transfercase gets jammed.

Sounds like it is a relay problem which requires testing with a volt meter from the switch on the dash to the transfer case and the wiring harness

tap on the 4wd motor on the transfer case while someone is pushing the button, if engages you need a new motor

the four wheel drive uses vacuum hub locks. there is a vacuum solenoid on the passenger firewall in front of the battery box. sounds like you need a updated solenoid and possibly one or both hub locks. what happens is the old style solenoid vent allows water to get in and the hub locks freeze or stop working because of the water. the new style has a cover over the vent to prevent water from getting in.

check for leaks in the vacuum, Jeep used a vacuum switch for the front axle during that time on the dana 30, it may have a leak or just worn where its not fully engaging and lockign all the way. It may not be holding the air as well to keep it engaged. Its a small tube.