Working on the boss's 98. He tells me he's has issues getting into 4hi and 4lo. Says he hears a relay clicking behind the dash switch and nothing. This is ESOF.

After some reading here I lubed the front diff. at the visible fork and it seems I can now get into 4hi on-demand as I should. What I can't get is 4lo.

All brake lights work (even the 3rd) and I have the truck in neutral w/ the brake applied when attempting to shift to 4lo.

I get the 4x4 light on the dash when in 4hi and hear the front diff click in. When changing to 4lo I hear nothing and there is no light on the dash indicating 4lo, just the 4x4 light as with 4hi.

I've jacked the front end up to clear the front tires and here's the results:

2 wheel drive- front tires turn independent of each other as they should (not linked together). The front driveshaft turns w/ the drivers side tire.

4hi- Tuning the drivers wheel forward turns the pass. side tire backwards. Front driveshaft does not move.

4lo- No light on dash (other than the 4x4hi light), no audible clunk or motor noise from the xfer case or anywhere.

From the interwebs I believe fuse 17 under the hood powers the xfer case and fuse 23 in the cab is part of this as well. Both fuses are good.


This is all I know right now. I tried tapping gently on the back of the xfer case and got nothing. Keep in mind I'm a total newb to 4x4 so don't be surprised if I don't know what you are talking about, lol... I suspect it's the motor on the xfer case, but that's just a WAG.

 

Update: After reading through the owners manual I checked all the fuses that were related to the GEM module. I found that the 5A fuse at position 20 was MISSING. I pulled the 5A for the instrument panel to test. Key in on position, foot on brake and trans. in neutral I now get 4 low, as indicated by the clunk from the xfer case and the "Low Range" indicator on the dash. It switches in and out just fine.

Thought I had it all then noticed that when I tried to get back into 2wd that the 4x4 light was on indicating I was still in 4hi and I did not hear the front diff unlock as I had before I replaced the missing fuse. The only way I could get it out was to turn the switch to 2wd and turn the truck off. When I turned the key back on it was out of 4x4 but now I cannot get it to engage 4hi. No noise at all, not even the relay click from behind the switch.

I know the front works off of vacuum and it appears to be fine. Is it possible that I just need to fire it up to get my vacuum back and try it again? It seemed to switch into 4hi just fine w/o it running but idk.

 

Since I've answered my own question here is the resolve to this particular issue. Maybe it will save someone else the aggravation of digging through so many threads to get some input.

After replacing the 5A fuse in position 20 and lubing the front vacuum actuator I took it for a test drive today and can now shift to 4x4hi on the fly, and 4x4 low when in neutral/foot on brake. It will also disengage 4lo just fine and even jumps out of 4hi as it should. Sometimes it takes it a few seconds but I think once the vac. diaphram gets moving again all will be well.