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GMC Jimmy 4WD Problems



  • I bought a 98 GMC Jimmy SLS, 2 door, 4x4. When I got it it was in 2 hi, wouldn't go into 4 hi, but would lock and then unlock immediately in 4 low. Got it into 4 hi, now it's stuck. When you push the buttons for 2 hi or 4 lo, the light flashes on the button and the TCCM clicks 5 times, but nothing happens. After trying this a few times the light only flashes once quick and the TCCM clicks once. It goes back to a few flashes if you unplug the battery and wait a few minutes, but still no shifting. Brought it to Mr. Transmission, they told me it's the encoder motor, so I replaced it, no change though. Changed the TCCM too, no change. What else could possibly be wrong?

    Summary: stuck in 4 high, changed encoder motor, changed tccm, still wont shift out of 4 hi. TCCM clicks, and light flashes on button, but goes to only one click and flash after trying it a few times.
  • only a few more things to check. One is the vacume acuator under the battery, One is the vacume switch on your transfer case. And another is the switch on the front differential, I had a bad shift cable also on mine. Like I said its a lot of trouble trying to find out whats wrong. And yes don't forget the push button switch on your dash. I changed that too. About thirty dollars. but i didn't need it. Hope this will help
  • I just bought a 1999 Jimmy and Im not sure how the 4 wheel drive works. I hit the 4 wheel drive button and it just flashes. The first time I did it I heard a clanging sound in and out of 4 wheel drive. Even though the light flashes it seems to work in 4 wheel drive. When I drive it in a circle I can feel the tires fight each other. I dont have a clue what is suppose to happen. Is the light suppose to stay on or is flashing ok. I guess I need some tutoring on what to expect as far as the lights go. It only has 75k miles on it but undercarriage is rusty like from sitting a long time. I have the 4.3 vortech and only gets 14 mpg. Is it possible it stays in 4 wheel drive?
  • Lesss then a year ago I replaced both of the hub bearings on my Jimmy. Now it is starting to make the same noise it was making before. Can someone offer me a solution so I do not continue to put money on the same problem.
  • wnekwnek Posts: 2
    Push that truck off a cliff, I think GM jimmy was a test truck so GM could maintain continuous revenue from service charges...,
    I loved that small truck when it worked , once it falls apart there is no stopping to it...., here in Canada fuel pump replacement costed me $1300 lol after 1 year again the fuel gage failed after a year !!!! the fuel gage reader is in the fuel pump in the tank lol..., I need another $1300 to make my fuel gage work LOL !!!! now the truck rests off of the west coast in the ocean... I hope I never see that dancing fuel gage display ever again !!!!
  • revn57revn57 Posts: 3
    edited December 2011
    Engaged in 4H or 4L lights are solid and the front drive line turns. Cable is pulling with vacuum but no power to the front wheels. I removed the cable at the axle tried to get anything to engage buy pulling the coupler by hand in gear and in 4wd on jack stands with no luck. The shaft only moves about 1/2 inch. Wondering if that is enough to engage the coupler. Also, I would think that you would have vacuum in 4wd but none in 2wd. I have vacuum to the cable in both. Since I have vacuum in both 2 and 4wd, I wonder if it has been engaged for some time and has damaged something in the front diff. If this is not normal, what controls the vacuum coming from the transfer case?
  • Took the front diff apart and found a striped connetor gear. There was a broken shim that was blocking the slip gear. This kept the slip gear from engaging completly and stripped one edge of the connector gear. I am still wondering what blocks the vacuum when switched to 2wd.
  • I have a 1997 jimmy 4x4 won't engage, front axle does not lock. Thanks to this forum I have found several problems and fixed them. The vac. switch was stuck. I replaced it. The actuator was torn. I replaced it. The dash switch seems to be working fine because the TC does shift and the front driveshaft turns. It also shifts into 4lo. I have removed the vac. switch and pushed the ball up by hand and I get vac. at the actuator hose. I installed a vac. gauge in the actuator hose and observed that when the 4hi button is pushed there is a verry quick jump of the needle to about 4" then it immediately drops to zero again. This occurs whether or not the vehicle is in motion. If I then shift into 4lo nothing happens on the vac. gauge. However, when I shift back to 4hi the vac.reading is 1.5", and stays there until I shift into 2hi. I'm thinking that there is an internal TC problem that is causing the switch to remain down. Has anyone had this problem. Also what does the electric switch on the front differential do. I haven't checked it yet, will do so tomorrow. Thanks for your help.
  • Hello revn57, I'm not sure but I think that the vacuum is blocked by the switch on the transfer case and is vented off of the actuator by the same switch . That's what the third hose is for. It is the vent. One hose goes to the engine to supply vacuum. One goes to the actuator to operate the cable. one just goes to the atmosphere to allow the actuator to release vacuum through it.
  • I checked the front axle switch, it seems ok. although there is 12 volts at the switch conector. I was expecting 5 volts... I took the new vacuum switch out of the transfer case again and pushed the ball in by hand and rotated the front drive shaft with the engine running and the front wheels turned, so the actuater, cable and axle are ok. I removed the transfer case shift motor and shifted the shaft by hand. The part that pushes the switch up moved as I turned the shaft. I then installed the vacuum switch with the case in 4lo and turned the front driveshaft by hand with the engine running. The front wheels did not turn. My conclusion is that the new switch is defective or wrong. I will get annother switch tomorrow this time from the GMC dealer.
  • I fixed mine by changing the encoder motor on the transfer case. It sounded like it was going in but it didnt work sometimes, Hope you get yours fixed soon four wheel drive season is upon us
  • I was right. The new switch that I put in saturday was either defective or wrong. I just put in a new OEM switch and the 4wd works perfectly now. Apparently there are two different transfer cases mine is a 233-c I don't know the number of the other case. The part no. for the OEM switch is 89059420 . I will return the defective switch tomorrow for a refund. I hope that my experience with this has helped someone. Lesson learned, use high quality parts the first time. I don't know if the two different cases use two different switches or not, I'll find out tomorrow.
  • Check vacuum line coming off the PVC going to in front of the fire wall drivers side for leaks!
  • zorad1000zorad1000 Posts: 5
    Well the actuator has failed again because of trans fluid getting in it . I guess I should have blown out the lines the first time. However I have found a manual cable shift kit for the front axle. I will install this manual shifter cable soon. the kit is available at Summit. costs about $160.
  • I recently had some tires swapped over from winter to summer and upon getting a front end alignment I was told 2 bolts were rounded. One on each side and one front and one rear. Is this a hadr fix? Sould I just change the nuts rounded or just change all 4 bolts. How hard is it and what do I need. Thanks Mike
  • my friend trans fluid is getting in because transfercase seal is leaking into your transmission I had to fix mine hope this helps
  • The auto 4wd, the 4wd hi and the 4wd lo lights just blink until 2wd button is pushed. The drive shaft from the transfer case turns but the front differential wont engage. Have checked fuses and replaced actuator. The battery was disconnected for a good 45 mins while I played around with the actuator. The fluid level in the differential is good. Have tried to trace the vacuum line but I keep getting lost.
  • I have had the same problem. I just had both front wheel hubs replaced at 107K miles for $750. I had to have mine replaced because to anti-lock
    brake sensor failed in the left hub and the right one was noisy. I don't think there is a solution for this problems. Just like there seems to be no solution for leaking intake manifold gaskets or the flaky fuel gauges or the failing fuel pump. The is a nice "little" SUV, when it runs!
  • I have a 2000 jimmy and it is doing exactly as yours did. I was wondering if you ever got it figured out. If you have any advice that would be great.
  • shellstershellster Posts: 1
    edited April 2013
    I stumbled on to this site and found it to very informational. But have searched and searched and have not found the answer I'm looking for. While in 4hi, driving up a very steep hill (it performs better) the vehicle is fine. But when I turn the corner, it hesitates as if it's struggling about to cut off or something. Another time I forgot to disengage 4hi, I tried backing into a parking spot and the same hesitation occurs. Is my jimmy sick or just too old. Feel free to be brutally honest. Mind you I just purchased jimmy 6wks ago. Trip to the folks I bought it from is planned tomorrow.
  • Sounds like you need a tune up. But when in 4 wheel drive all axles are turning and make it difficult to steer. Try taking it out of four hi when you are parking or backing up. Just hard to get used to four wheel drive. It really makes a difference if the road is snow covered or not when steering. Hope this helps. When its hard to steer that means your front wheels are engaged.
  • jim579jim579 Posts: 1
    What fuse did u replace under the hood.? My works fine in 2w but when punch 4 w button ..nothing
  • Check your encoder motor it might be pulling power and blowing fuses I had to change mine working fine now.
  • Just found out my front drive-shaft is bad on my all wheel drive GMC Jimmy,can I just take it out and drive with out it- do I need it?
  • you can drive it but you wont have four wheel drive
  • My friend when transmission fluid is getting into your vacum acuator motor next to the batter case its because you need a new seal between your transfer case and transmissio I blew out two or three acuators before i got it fixed. Hope this helps
  • Usually with front hubs I found that the more expensive hubs are worth it I changed four or five hubs out before I found out that the cheaper ones didn't last more than a year or two. Salt and dirt mess up the sensors. Hope this helps
  • I know this is an old topic but I think I may find some help with my 2000 gmc sierra 1500. My lights act normal but the only 4wd mode that locks the front wheels is auto. All the signs of 4wd working r there except the front wheel spin. The gear ratio is dropped in low the think when its initiated the whole nine. But the only way they pull is in auto
  • bg333bg333 Posts: 2
    tar99 said:

    My 1997 GMC won't engage 4wd. The transfer case will engage low gear, the lights on the dash switch light up (2wd is burned out but 4lo and 4hi will light and stay constant when pressed). The front drive shaft definitely turns. There is vacuum at the acutator, and the cable pulls with an audible click.

    There is still no 4wd. Is there a problem in the differential? If so, is there something specific I should look for?

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