Wierd 4x4 problem 1997 GMC

My 1997 GMC jimmy started acting rather wierd the other day while driving back to my house, as i was crusing down the thruway the 4HI light would blink in no particular order, it didnt seem like the truck was going into 4x4 but i pulled over and pressed the 2hi button, it clicked but i didnt notice a drivability difference. it stoped momentarilly then started again, now today the 4x4 has stopped working completly however the 4HI light will kinda flash whenever it feels like. almost like its trying to piss me off.
there is no hesitationas if it were entering 4x4. ive searched far and wide and ive been told anything from faulty vaccum line, 4x4 control module, the encoder motor, bad transfer case and anyother component that could be associated with the driveline. If i cant figure it out i will just take it to the chevy dealer and eat the 90 bucks an hour labor rate. Thanks and any help couold be appreciated

Did you ever find out what the problem was? My dads 99 gmc jimmy just started doing the exact same thing this week.

I have a 1999 jimmy that does pretty much the same thing and I have replaced the contol module on the transfer case and the actuator on the floor/door panel on the passenger side. Still have the problem. Now I am about $800 in the hole. The next thing I was going to replace is the switch in the dash. My vehicle will also switch the transfer case into 4wd hi and or low while driving down the damn highway. I can't believe GM hasn't done anything about this. Anyone have any help. Thanks.

. . . My vehicle will also switch the transfer case into 4wd hi and or low while driving down the damn highway. . . .
Are you saying it goes into 4x4 Low, on the fly, at highway speeds?

Are you saying it goes into 4x4 Low, on the fly, at highway speeds?
Hello there, yes, the vehicle will switch right into 4wd low and sometimes 4wd hi while driving right down the hightway, other times it will switch when you start the vehicle. I read someone else had a similar problem and said something about a vac hose on the transfer case. I will check this out. Do you have any other suggestions?? Anything will be greatly appreciated. I will try whatever you suggest. Also, what do you think about the switch on the dash? My theory is that the switch is working correctly because when you push the selector buttons, it will do what you say. The switch, the module on the floor and the actuator all do what they are supposed to do when you select it. HELP!!

Thank you,

Pampersman

I seriously doubt it’s the switch on the dash, might be the ignition switch. I would say it’s an electrical problem somewhere, as opposed to a vacuum or mechanical problem. If the shifting on 97-99 is anything similar to my 95, there is an electric component in the system to prevent the transmission from going into 4x4 Low unless the vehicle is stopped and in neutral. I would try to track this down.

Sometimes electrical problems are hard to diagnose when several components interact with each other. I saw a Ford pickup that wouldn’t shift into 4x4 and the problems was with the electric fan clutch on the engine, as both components shared the same circuit and when the electric clutch failed it caused an open circuit in the system.

Good Luck and let us know what you find.

Did you guys find anything out about this problem what is causing it? My girlfriends jimmy is doing the same thing and i dont have the money to just start dumping it and playing a guessing game on what i should try to replace first?

Just to let everyone know. The problem with my dads 99 gmc jimmy was the transfercase control module that is located behind the passengers side kick panel.

its good u fixed the problem but this thread is a year old. in the future, please refrain from posting in old threads.