Jimmy Auto 4WD Problems...

12-12-2009, 12:46 AM
I have a 2000 GMC Jimmy with the 4 button "Auto 4WD" option, I believe it's the NP8 transfer case.

I had the trans rebuilt and when i got it home I decide to check the 4WD since the tcase had been out of it. everything worked at first but then I heard relays clicking and the service 4wd light button came on and it was stuck in auto 4wd. I shut the truck off and still stuck in 4wd. I disconnected the battery and when I started it back up it was now in 4 hi. Now i was able to press 2wd and it was fine. Untill the next time i selected auto 4wd...same thing. After a while I no longer had to diconnect the battery, now i just have to shut the truck off and start it back up...back to 4 hi...press 2 hi and it's fine. 4 hi seems to work fine, 4 lo seems to work fine, however, auto 4wd seems to actually be simply 4 hi, not auto. Every time I press auto 4wd the service 4wd light comes on and I have to shut the truck off in order to get it back in to 2wd.

I really dont know too much about 4wd but I'm otherwise pretty sharp around the garage. I'm shure I can fix this IF I only knew what the problem WAS. Could it just be the dash switch?

Please help...

12-12-2009, 01:43 PM
Welcome to AF. If it worked before the trans was done I would check the connections at the transfer case first.

12-13-2009, 02:19 AM

Funny you should mention connections as the next time I was under the truck I noticed a harness that was obviously routed under the front drive shaft BEFORE the trans was rebuilt (I could see the little christmas tree wire tie and where it was SUPPOSED to be) was now routed OVER the driveshaft and actually siting ON the driveshaft. it rubbed through the black convoluted tubing and into the insulation some. When I took it back to the trans shop and pointed out that I had to wire tie the harnesss up off the driveshaft the F#@*ing guy had the nerve to tell me "Yeah, looks good to me! Good job!" Needless to say I concluded two things...1, don't ever do buisness with that shop again and 2, it might just be my problem. I just figured I'd ask as I wasn't sure if a wire could be responsible for this issue or not. I didn't want to go messing with the harness as there's not a lot of extra wire to play with before I start to get into trouble and I wanted to be certain I wasn't just wasting my time (and wire) on it.

12-13-2009, 02:21 AM
In hind sight there really isn't any copper exposed and even if there was, it's tied up to where it really can't make contact with anything to short out. Maybe the problems lies elswhere?

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