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GMC Jimmy 4WD Problems

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Comments

  • repairdogrepairdog Member Posts: 948
    4 and 6 or what my conversion came up with also but never had to find metric ones - alittle slow down here getting on world standards. Never used silicon. If a 3 button with the vac switch on the transfer lots needed but normally only about 2 feet/meters of smaller under hood are bad. Make sure you get the lines right if you run all the ones to the transfer case on 3 button.
  • rrrccc01rrrccc01 Member Posts: 5
    RD, thanks for your reply.

    Things are getting worse and worse! I have some questions but I’ll fill in details first.

    1998 GMC Jimmy
    3 button 2 Hi - 4 hi - 4 lo
    NP01 Transfer case (233?)

    Original problem, TCCM needs to be rebooted on a regular basis.

    Done so far in this order:
    1.Replaced actuator under battery – no change
    2.Replaced TC sensor – no change
    3.Replaced TCCM with a used one from ebay - no change
    4.Replaced at same time –
    a.TC fluid
    b.Replaced Front Diff oil
    c.Replaced TC encoder motor
    d.Replaced vacuum lines to TC

    Now no 4wd at all, 4 hi and 4 lo flash then back to 2-hi

    I am stationed in the Persian Gulf and am unable to do the work myself, physical injury, but, I have a reasonably knowledgeable local mechanic that does what I tell him, that is I supervise!

    Questions

    1.Is this indeed a 233 TC?
    2.I have seen the phrase "firewall solenoid" in the newsgroup, is this the actuator under the battery or is it a different part?
    3.When my guy ran the new vacuum lines from the TC sensor, he told me one was a breather. Is this so? If not where do all three 3 hoses go? What did he miss?
    4.I have seen repeated comments regarding the encoder motor, 4 hi and 4 low. Before installing the new motor we connected it to the plug and pushed the 4-hi button and it did move. So last and for all, does the TC encoder motor do anything when shifting from 2wd to 4 hi?

    HELP
  • rrrccc01rrrccc01 Member Posts: 5
    More Information,

    New parts installed:
    Vacuum actuator
    TC Vacuum switch
    TC encoder motor
    vacuum hoses from TC vacuum switch
    Front Differential oil
    TC fluid (Red dexron II)

    Checked vacuum at actuator under battery, none!

    Hooked up direct vacuum to actuator and it does pull the cable!

    So this means no vacuum from 3 port switch on TC to actuator! Further research on vacuum:

    I have identified the hoses on the switch on the TC:

    1 constant vacuum from intake set up
    2 to vacuum actuator under battery
    3 is release vent for sifting back to 2wd.

    To me, this means that when the ball is pushed or released by something in the TC to either release or send vacuum to the actuator to engage/disengage the front axle. What pushes the Ball? When? I presume something in the TC moves, probably moved by the encoder motor? I hear the TC encoder motor running when pushing the 4-Hi switch.

    Is it possible that the hoses were connected incorrectly to the TC vacuum switch? I know it is keyed, so this shouldn't be possible but hose 1 (constant vacuum) and 2 (vent) are the same size and could theoretically be switched and would explain why there is no vacuum to the actuator under the battery. For the sake of argument, which hose should be where, clockwise from the "key" on the switch?

    Also, is it possible to install the TC encoder motor in the wrong position, i.e. the motor thinks it's in 4wd but the truck is in 2wd? I hear it run when I push the 4-hi and 4-lo switches, so it's doing something!

    Last but not least, I am out here on the fringe of the world so getting parts is a battle! The last one I can think of is the switch on the front axle/diff; anyone have the part number?

    Again HELP!!!!!!!!!!!!!!!
  • repairdogrepairdog Member Posts: 948
    You got it. The 3 port vac switch on the TC is the most likely item to fail but its new. When in 2wd the ball on the switch bottom is down and the vac shut off while the vent line (also connected to the TC vent) is connected to the front actuator so its uncoupled the front axle. When 4Hi selected the encoder motor steps to move a fork in the TC that engages the front driveshaft and pushes the ball up on the 3 port vac switch that opens the port so the engine vac now is to the front actuator (and shuts off the vent port to actuator). How about the dash switch - I just posted 2 answers on how that works with 8 volts and TCCM watches return from switch each mode with a diff resistance value (Dorman about $35). That front coupler sensor is gm#15598481. The firewall solenoid is for autotrac 4 button cases only so you don't have. You can find most parts online at the dorman, smpcorp, or rockauto sites all with pics and many cross ref #s.
  • rodney7rodney7 Member Posts: 1
    I have a 2002 Blazer 4x4 with 2wd 4hi 4lo and auto 4wd buttons the transfer case is always engaged (front drive shaft always turns) is this supposed to be that way? is there reason for concern? and if its not supposed to do that is there a common problem I should look for?
    thank you
    Rod
  • repairdogrepairdog Member Posts: 948
    The 4 button Autotrac transfer cases NP236 always have the driveshaft connected by desigh so no worries. This is always spinning to accomodate the Auto4wd selection that senses wheel spin and engages power to the front differential when needed. (The 3 button cases NP233 does not and it engages when 4wd is selected)
  • modigitymodigity Member Posts: 4
    I have the same Auto 4wd system on my 2001 Jimmy 4x4 (Diamond Edition). My 4wd will work for a while, then the Service 4wd light will come on. Then a week later they 4wd works fine again, then a week later... well, you get the point.
    Any clue to what might me causing this? I would like to get a direction before I start tearing into this thing. And with 6-10 inches of snow in the forecast for tomorrow, I really should go to town on it tonight! Also, is there an easy way to change the transfer case fluid? Thanks!
  • repairdogrepairdog Member Posts: 948
    As for fixing look back up at all the answers I posted - covers most. As for fluid there are 2 plugs - bottom to drain and top to fill and use the blue syn fluid GMonly 2 qts (not red Dexron!). Cold can cause some binding and sensor sticking. If its the computer pull the AWD and 4wd fuses for 30 min or the battery cable and see if the reboot fixes.
  • pault732pault732 Member Posts: 2
    big ice strom in the notrh east left me trying to engage my 4wd on my 98 jimmy 3 button panal on dash the 4wd low and 4wd hi just star blinking and the go back to 2wd after I shut the car down I here a major clicking sound behind the glove box
    I took the glove box out and the sound seems to be coming out from behind the back of the wheel well I dont want to disconect any electronics untill I have a better idea what im looking for any idea what im hering ?
  • repairdogrepairdog Member Posts: 948
    TCCM or 4wd computer is in the pass side kick panel and that maybe it or the front axle has the axle coupler on the pass side that must engage - push switch, vac form engine down to transfer case 3 port switch activated by the encoder motor on the case. Check vac lines, switches and sensors - many posts on all that.
  • rbcellirbcelli Member Posts: 4
    I have a 2000 Jimmy
    When the auto 4wd drive button is pressed, the light stays on, but the front wheels won't turn as needed. ( I tested this in my ice covered driveway) Last week the service 4wd light was on often until I disconnected the battery for .5 hours. Now the 4wd seems ok, but not the auto 4wd.
    I've read several posts that mentioned vacuum lines and actuators,but they seemed to be related to the 4wd not working at all, not the auto 4wd .....sooooo. I still don't know what to look for
    Please help, Thanks
  • repairdogrepairdog Member Posts: 948
    The auto 4wd is controlled by the TCCM commanding the encoder motor to select the proper setting tpo the transfer case clutchy packs as the wheels slip so, are you sure that auto doesn't work? If 4Hi and 4Lo work and the ABS is operating usually AUTO 4WD is ok.
  • rbcellirbcelli Member Posts: 4
    Thanks for the reply
    Yes,4hi does work....I don't use 4lo though. I know this, I was at a traffic light the other day on snow in auto 4wd. When I tried to move, the back wheels were spinning, but the front never engaged so I pressed 4hi. And again it happened in the driveway.
  • rbcellirbcelli Member Posts: 4
    Is it possible that the button on the dash is at fault?
  • repairdogrepairdog Member Posts: 948
    Yes, the TCCM receives different voltages from the dash switch to tell it waht mode to select, but not commonly bad.
  • rbcellirbcelli Member Posts: 4
    I now have discovered the auto 4wd works when in reverse but not forward.....I tested this several times now. It kicks in immediately when backing up, but when I put it in drive...nothing. The rear wheels just spin. Any thoughts?
  • howie59howie59 Member Posts: 11
    I fixed the vacucum leak at fire wall and still get inyermittin 4x4 to work i also have ABS brake issues when i break hard it shivers any relation ships?
  • repairdogrepairdog Member Posts: 948
    Remember that auto only works to supply power to the front diff when wheel slip occurs (i.e. is sensed via a differing speed between the TC mounted speed sensors and the front hub speed sensors and is also speed dependent. You may not have a problem with the encoder motor or speed sensors - I would have the dealer use their scan tool to tell you - less than $100 and cheaper than throwing parts at it - if nothing wrong anyway.
  • repairdogrepairdog Member Posts: 948
    There are many parts/areas to look at as the posts have covered. The ABS should pulse the brakes and you should hear them and if the rotors are rusty you will pull to one side then after a few full stops with the ABS engaging it should clear up - this all assumes the brake syytem is fullt functional and rotors don't grab (warped) during normal breaking. There are speed sensors in each hub that tell the ABS whats happening and in the transfer case on 4wds for the rears (in the transmission on 2wd for rear).
  • howie59howie59 Member Posts: 11
    Thank you repairdog I replaced both wheel hub assemblies and spliced in the vacuum line at the fire wall I also replaced the rear brake pads and rotated tires THE WHEELS ARE FINALLY QUIET THE BRAKES DO NOT SHIVER AND ALL LIGHTS ON DASH ARE OFF :)
    I am afraid to push the dash board 4 buttons :confuse:
    prior to working on the hubs - I fixed the vacuum leak at firewall, the buttons would work to engage most times i tried. a few times I had a hard time swithing between the buttons they would engage/disingage but now I replaced hubs and I am so happy the wheels are quiet and the brakes work I am afraid to try the buttons it is now in 2 wheel and cant aford to fix any computer problems at this time
    I feel so good about eveerything its like a new truck quiet and tight
    should i disconnect battery or pull fuses or cross my fingers and push the buttons???????????
  • repairdogrepairdog Member Posts: 948
    Try it. 4Hi first then 4Lo. Always can put the battery cable later to reset TCCM if a problem. If the encoder motor jams up then hit it a few times and see if that frees it. All wires should be uncut and connected of course.
  • howie59howie59 Member Posts: 11
    sorry I thought everything was ok NOW the abs and brake light come on once i press the pedal and the 4 button switch tranfer dash only lights but does not engage the 4 wd system? I really hope you could offer more info because you have helped so much so far and I am on a limmited budget and I am handy with tools but not a mechanic at all but cant aford a dealer I am working with a garage mechanic he performed the work youu have advised so far, and I think we are almost there I hope

    so far we changed both front hubs and inspected front brake pads [lots left] and we changed the rear pads and trued the rotor Thank for your or anyones help I have inspection due april! :confuse:
  • dmathydmathy Member Posts: 2
    The light on the dash will come on and i can hear a click like the 4 wheel drive is working but the front tires wont lock I have checked all the plugs on the tranfer case . I have tried everything to get the 4 wheel drive to work :mad: can some one help
  • bearpawprobearpawpro Member Posts: 1
    I have a 2001 GMC Jimmy that has been in the shop 4 times in the last month. When the 4wd is changed to 2wd and back to 4wd, the abs light comes on. The shop changed the abs sensor, only to have it happen again. The Jimmy is visiting the mechanic again, and they have finally admitted defeat. Does anyone have a clue what is going on?
  • repairdogrepairdog Member Posts: 948
    Each front hub has an ABS sensor and the rear one is in the transfer case. Fronts in rusty areas (salt) have had the sensors raise up as the rust deposits on the sensor mounting point so the fix is remove, carfully sand the mounting point keeping the material out of the hub hole, reinstall -OK now. If you are over 100k just but 2 new hubs for about $300 parts or GM sells the sensors. GM has a scanner to read the ABS codes so that would be my suggestion. GM has the bulletins on these maintenance intensive vehicles, as they age not gracefully. Drive well and run well but you gotta keep on them - I am constantly changing sensors and parts to keep my 4 running.
  • lotech097lotech097 Member Posts: 1
    I also have a problem or concern. Today both my ABS and park brake light on the dash came on. The problem started when I hit a pot hole, I checked the sensors in the frt hubs and they look fine, is there anymore sensors I should be checkin, I heard there was one on the T/C. Is this true, and also will a code reader tell me the problem ? Thanks
  • howie59howie59 Member Posts: 11
    I also have brake lite on after a jerk or wet condition and 4x4 is struck in auto mode??
    I tried diconecting bat
  • repairdogrepairdog Member Posts: 948
    Depends on year model (and must assume you mean the ABS brake light), but would have to say the front wheel ABS sensor connecor on the frame about 2 ft up front the sensor is getting wet, the wire has a cut, or the mount has rust deposits on the hub so sensor cal off - GM bulletin on the rust requires unbolting sensor and cleaning mounting point without getting crap in the hub.
    4wd check the vac lines under hood first and if 99up with autotrac (as you said auto) then put the case in neutral by pushing the 2 buttons at the same time (marked on 4 button panel), then select 2Hi and it sould work. Then search all the posts on 4wd fixes already posted.
  • howie59howie59 Member Posts: 11
    thanks repairdog can you tell me which two buttons at same time?? sorry but i am seriously challenged in the brain?[lol] actually i apriciate your knowledge on this truck mine is 2001 I wish I would researched this truck better after seeing all these problems everyone has Next the ffuel pump I bet?
  • repairdogrepairdog Member Posts: 948
    OK, see that Neutral line that connects the 2wd and 4Lo buttons - press them at the same time. Hey and good news yours also has the secondary air injection pump and valves that only 99-01 had! Good luck.
  • unicorn747unicorn747 Member Posts: 15
    HAVE YOU HEARD OF ANY PROBLEMS WITH THE WHEEL BEARING & HUB ASSEMBLY'S ON THE 2001 GMC JIMMY'S? FROM WHAT I'VE READ A FEW PEOPLE HAVE MADE COMPLAINT'S ABOUT THEM & IT SEEM'S AS THOUGH MY NEED'S REPLACING ALSO. DO YOU HAVE ANY IDEA OF WHY THIS MIGHT BE?? JUST CURIOUS! THANKS,UNICORN747
  • repairdogrepairdog Member Posts: 948
    All Blazers have the same issues and yes I did my 01 4wd at 90k miles both hubs , ball joints, and then the CV axle on one side went. My 98 2wd went at 100k then the other side at 120k. My guess is if the vehicle is or was in a salt used road area they will go faster as the salt get sucked in the back side of the wheel/rim and you can see the sealed bearing back in there - you can only seal it so well and with rough roads and conditions and GM did not overbuild these vehicles!
  • frustrated31frustrated31 Member Posts: 1
    Hi, i have a 2000 jimmy with 105,000 miles and in the last 2 years the following has happened...A/C broke then Tranny went, gas gauge broke, then door seal-Front passenger leaks badly in the rain(otherwise its in garage), my tranny broke YES....a second time. Now radiator leaks and the 4wd isnt working. my hubby put the vac line back on when he noticed it had fallen off (putting in the tranny a second time) and it worked...well for a day now it doesnt. I push the 4hi button and both 4hi and 4lo blink and then it goes back 2hi by itself. Sometimes both 4hi and 4lo blink and stay lit and i can't get it to go back into 2hi..so i guess my question is WHAT"S NEXT???? what do i look for?(a new truck ..LOL)
  • mobiusdieselmobiusdiesel Member Posts: 5
    Ive had same problems with the 4X4 in my 98 Jimmy... I decided to replace all rubber vacuum lines in truck to Syn-Flex lines which are plastic airlines usually made for airride systems in Long-Haul trucks. Worked like a charm but was very time consuming to replace all the fittings for the new style lines. However 70000k since and not one problem. with 4X4 , A\C or fuel mileage. hope this helps. Mobius
  • repairdogrepairdog Member Posts: 948
    Depends on case type but would guess a 3 button dash switch (No auto function) and if so a np233 transfer case and it has the vac switch on the drivers side of the transfer case and 3 sets of lines running down there - check them first then do a search in the posts for the many on fixing all 4wd problems.
  • dipstickydipsticky Member Posts: 1
    I just rebuilt my first tranny and have reinstalled it (4L60E) My dumb question of the day is, Is there a correct position for the 3 port vacuum switch on the top of the transfer case, or will any position do? It would seem that if it had to go in a particular orientation, the plug would be a unique shape.

    The reason I ask is, I installed it once and when I test drove it, I thought I had something wrong internally. The car dragged in forward and wouldn't back up at all. I now suspect that it was the transfer case. Originally it all worked fine, just reverse was worn out. When I reinstalled the rear drive shaft, the TCase output shaft wouldn't turn, like last time. The transmission itself seems okay.
  • repairdogrepairdog Member Posts: 948
    The rubber vac top of the 3 port switch is keyed or has a distinct notch on it so only one way it fits correctly on the switch itself which just is screwed in till tight.
  • helpmewithgmchelpmewithgmc Member Posts: 1
    I have a 2000 Jimmy 4wd. When I start it, the 4wd error light comes on and never turns off. I don't have any leaking fluids, any strange noises, etc. Any help would be great.
  • repairdogrepairdog Member Posts: 948
    Could be many items so look thru the posts. Try a 30 min battery disconnect to reset the 4wd computer as first step. Look at the vac lines under hood for rot/breaks and replace as necessary 5/32".
  • vguidovguido Member Posts: 2
    i have a 97 jimmy while driving on the freeway it make a whining noise from the transfer case i will shift it into 4hi and back to 2hi and the noise clear up or if i dont hear it with the radio up when i slow down it get real load then stops when i stop.the light is always in 2hi and never changes. also my abs when i slow down to 5 mph the abs grab ive pulled the fuse, is there a fix for this i heard about cleaning the senors would work but just not sure. thanks
  • mtrotter70mtrotter70 Member Posts: 3
    I had the exact same problem with the whining noise on my 95 blazer. Problem resolved by replacing the vacuum switch on top of the transfer case. It leaks down the vacuum, which causes the front axle to partially engage and moan/whine. The vacuum switch is a very inexpensive repair.
  • merandsmerands Member Posts: 1
    I am experiencing the exact problem with my 95 blazer. Can you please tell me how to replace the vacuum switch. I was unsuccessful in locating instructions on alldatadiy.com for this repair. Your help is greatly appreciated.
    Thanks
    Brad
    merands@aol.com
  • howie59howie59 Member Posts: 11
    I have a 2001 4x4 GMC Jimmy with auto 4 button switch that is stuck in auto mode and the ABS -brake is always on
    Things I have tried
    disconnected battery for 30 minutes
    repaired one disconted vacuum line near the intake manifold
    replaced both front wheel bearings/hubs

    I have read most posts about this and dont know what to do next
  • ahustonahuston Member Posts: 1
    Auto 4x4 light,2H,4H and 4L lights flash in the dash often. Seems like engine will stall for a quick second then the service 4x4 light flashes on and sometimes stays on. Also noticed clicking sound from right hand lower kick panel when the 4x4 lights flash. 4x4 will engage when buttons are pushed. Have already replaced right front ABS sensor, tried other encoder motor and problems still occur-PLEASE HELP! :confuse:
  • chevy22chevy22 Member Posts: 1
    Everything works like it should,but where the cable pulls
    on the front axle to lock it in nothing happens.I tried
    to manually put it in but it still doesn't work.Was wondering what couldbe wrong inside the front differential
  • thesweetrosslgthesweetrosslg Member Posts: 28
    OK today i feel really stupid after months of wondering what the heck happened and why the 4 wheel drive stoped working i decided to go down the line and check the fuses well apparently fuse 19 was bad which works the 4wd switch box i guess i changed the fuse and i now see the lights light up and i can feel it kick on when i put it in 4LO
    But amm wondering i had some help from a friends we lifted all 4 wheel up using 1 jack in the front and 2 jacks in the back
    got all 4 wheels of the ground i wanted to just see if the 4 wheel drive works still and i dont understand how come the front wheels dont spin is it something that is just because it has to be on the ground will the Front wheels not spin or engage if the jimmy is not on the ground or is something still wrong check the vacuum lines everything seems to be fine cant think of what the problem could be please help thank you
  • cacyrccacyrc Member Posts: 1
    We got a part (4wd switch) from an auto salvage yard because we thought it would fix the issue of the buttons being stuck. When we connect the part you can push the 4wd buttons in but now they do not light up as they used to. We are guessing that we just got another bad part. We also checked the fuses and they are fine. Does this sound like the problem to you too?

    Thanks!
  • frekeyguyfrekeyguy Member Posts: 5
    Are you trying to change from 4WD to 2WD when you are driving?

    I think its safer, if you pull over, put it in neutral, and change over to 2WD or 4WD.

    Mine jimmy's at about 150miles, 250kms, and my truck shifts from 2wd to 4wd to 4wd low perfect, I just keep replacing the trasfercase fluid every summer...its easy and so cheap to do.
  • scarelloscarello Member Posts: 1
    I have a 1995 GMC Jimmy w/145k

    When you engage 4WD High, while rolling in 2WD Drive, it has a brief delay and you can "Feel" and hear it engage, but when you go back to 2WD, while rolling in 4WD Drive, it seems to wind out like it's in a Low Gear and seem to hear/feel mechanical "Grinding" then almost a loud bang and it goes back into 2WD and drives normally.

    I would almost think whatever engages or disengages the different modes is not doing so completely.

    Any ideas?

    Thanks everyone
  • abbyteedabbyteed Member Posts: 1
    I have a 2001 GMC Jimmy SLS with 130,000 km. It will not shift into 4Hi, Auto4wd or 4Lo. The TCCM has been checked and it is OK, and the shifter motor is OK and the transfer case shifts... BUT... when I push any of the buttons, the lights just flash and flash for a couple of minutes, and you can feel like it is attempting to shift, but it never happens and eventually the vehicle goes back to 2Hi. I don't know what else could be the problem if it is not the transfer case, shifter motor, or TCCM.

    Any suggestions would be greatly appreciated! Thanks in advance.
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