87 jimmy 4X4 problem

When I switch to 4 low or high the light comes on indicating that it is in that gear but i am still in rear wheel drive only??. Usually on the indicator it will light up the two front wheels showing that i am in 4 wheel drive but the only thing that lights up is the indicator next to 4 low or 4 high??

I had the same problem on my '91. It's the vacume switch on the transfer case(or around the area I don't remember exactly) It locks in the front differential. It's common on Jimmys/Blazers. Hope this helps

Yip, vacuum module under the battery tray.

a free and quick tip. If you can't diagnose the vacuum leack, reset your computer by disconnecting the battery +lead for about an hour or so.

a free and quick tip. If you can't diagnose the vacuum leack, reset your computer by disconnecting the battery +lead for about an hour or so.

His is vacuum based so that shouldn't work as well as with the electronic 4x4 systems on newer models.

Resetting the computer on a manual floor shift has no effect on the 4x4.