Hello! Am new to the forum; and have been doing alot of reading this morning. Excellent resource here for the DIY'er!

I recently bought a 1996 GMC Jimmy SLT out of a field for $350. Mint interior; solid body; needs some motor work. But it's a project for me to tinker with over the winter.

Now with a $350 gem like this I expected to have some other "issues" than what was disclosed by the previous owner. And aparently not uncommon to alot of these trucks; the push button 4wd doesn't function properly. From what I can diagnose the truck will not go into 4hi, and will only go into 4lo with alot of button pushing & effort. But when the 4lo finally activates, the rear diff locks and the front driveshaft locks. In any other setting; only 1 wheel spins in the rear and the front driveshaft spins freely. I do not think that the front tires engage in any setting. Now as I said; I have been doing a bunch of reading and later tonight when the weather improves I will be inspecting the vacuum lines & diaphragm under the battery as well as lines on the transfer case.

One issue that I have not read alot about is this: my 4wd switch will only operate with the truck in neutral. If it's in gear or park, pressing the buttons does nothing; no lights flashing, no sounds etc. When the trucks in neutral pushing the 4hi or 4lo button causes both lights to flash (possibly all 3 - I think the bulb is out on the 2hi) and then they all go out; but there is sounds of engagement/disengagement of something, I would assume trans. case.

Is that the symptoms of another issue?

Any help would be hugely appreciated!

 

It sounds like you may have a faulty switch. You can find a schematic and test the switch with a multimeter set to test continuity.

The only switch which is prohibited when in gear is a range change (either 2HI or 4HI to/from 4LO). A range switch should be allowed in both park and neutral, but park may result in a gear mismatch and a failed shift.