1999 Jimmy 4x4 problem

[jwlauman]

I have a 1999 jimmy with the 3 button four wheel drive selector. What happened was I was driving on highway in 2 wheel and a small humming began when I slowed down it got louder. It sounded like a drive line problem so I pushed the 4hi and the sound immediately went away. As soon as I go to put it back in 2 wheel it sounds like cards in bike spokes. When I put it back in 4hi it stops making the sound. I played with it trying to get it back into 2hi but no luck I don't believe it is throwing a code because the service 4wheel light is not on and the light on the selector doesn't continue to blink when I push them. It does go into 4hi and 4lo no problem. Can anyone point me in the right direction?

Thanks,
Jeff

[jwlauman]

Well I replaced the switch on top of the transfer case (the one with 3 hoses going into it) it was bad, and now I can drive in 2 wheel with no grinding of the gears. The 4 wheel drive still does not work though. The transfer case is working fine it shifts from 4 hi to 4 low but there is still no 4x4.

I pulled the batter and battery tray to check the vacume pump seemed to be working fine no rips or tears in boot and when i engaged 4 wheel it sucked in and pulled the cable fine. I also checked the switch in the front axle and it is ok.

This leads me to believe that a fork or the cable is broken in the front differential. On a snowy road when it says its in 4 wheel and I accelerate rear 2 tires spin and fronts don't all i hear is a grinding in front end.

I had the dealer scan the jimmy with a tech II this morning and no codes came up except for one under chassis F0: 4WAL 3 sensor I will have to double check thats what it was I can't find the piece of paper I wrote it down on.

Does anyone have any ideas what could be going on here.

[jwlauman]

No one has ever seen these problems before?

[MT-2500]

Did the dealer have any idea on it?
Try to post back the code no. they found.
MT

[jwlauman]

Hey thank you for replying, the only code that came up when it scanned was F0: 4WAL 3 sensor I don't know what this was and the guy didn't have time to check on it. I went back later to talk to the service tech and the owner basicaly told me to bring it and and they are not a "help desk" When I asked if he could look up some parts he said the parts guy was swamped and to come back. I told him where I wouldn't be buying parts, so I will have to try another dealer I don't know if I am welcome back there.

Tonight I pulled off the bracket where the cable goes into the front differential to see if that cable was broken (it wasn't) and see if I could see if the fork was bent or broken, but I couldn't see in there so It looks like I will have to pull the axle tubes off, disconect the driveshaft and pull out the dif. Both front cv joints are new and have less than 10,000 miles on them and look fine.

I don't know what else beside that shift fork could be causing this grinding in the front end.

I think there is something mechanicaly wrong so no sensors are showing out of range.