Alanmizzen Posted December 17, 2016 Share Posted December 17, 2016 Hey guys. So I'm in Vancouver bc and we've had crazy snow the last couple weeks with cold temps. I've been using my 4hi a bunch. It's been working great. But now when I go to shift out the light stays on. I shift in neutral reverse and go forward again and the light stays in. It comes out of 4x4 but the light stays on. I've tried all the ways but to no avail. Could it be something with the cold that cause something to stick? Is it bad to drive in 4 part time at highway speed? There's no snow on the main roads and I heard that it's not good to drive out of 4hi if the light is on. But I can't see it being good to drive in 4hi at highway speeds. Cheers guys Link to comment Share on other sites More sharing options...
yxmj Posted December 17, 2016 Share Posted December 17, 2016 You need to give more info what year Do you have a CAD The light in any year/set up in not the defining factor showing if 4x4 is engaged or disengaged....(I can make the light go on without a front driveshaft.....light says 4x4....pretty sure it isn't) If you do have a CAD.....my first best guess is to start there Link to comment Share on other sites More sharing options...
Alanmizzen Posted December 17, 2016 Author Share Posted December 17, 2016 It's an 88. Straight 6 it's not the on demand system like my 93 Cherokee has. Is that the CAD? Link to comment Share on other sites More sharing options...
desbennett004 Posted December 17, 2016 Share Posted December 17, 2016 Haha Vancouver cold! I'm in Calgary. I have my 99 in 4HI almost all winter, I just pop it out when I want to do sharp turns. No I'll effects. Not sure what the 4x4 light is switched on, but doesn't necessarily mean it's engaged. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
gogmorgo Posted December 17, 2016 Share Posted December 17, 2016 Not sure what you mean by On Demand, but I think you're referring to the full-time 4x4 of the optional 242 transfer case, which isn't an automatically engaging 4x4 like the cheap GM (and probably others) setup, it's an actual full-time 4x4 with a differential in the middle. I'm pretty confident it wasn't an option on any year MJ but I could be wrong. At any rate, no, the CAD (central axle disconnect) is a vacuum-engaged unit that connects and disconnects the two pieces of the front passenger axle shaft, which prevents the driveshaft from turning in 2wd, saving you an infinitesimal amount of fuel but mostly meaning kf you don't use 4x4 very often, it won't work the next time you try. Compare the front passenger side axle tubes on either Jeep. The XJ will be straight and simple, the MJ will have a bulge with some vacuum lines and maybe wires going to it. If your 4x4 works, great. If not, that's likely your problem. You can look into permanently locking the CAD, which is super easy and won't cause any problems down the road that you wouldn't have anyway, and you likely won't notice much if any hit on your mpg. As to the light, it's switched by a vacuum switch, which is driven by the same lines as the CAD, (which come off the Tcase, near the speedometer assembly in the tail housing). I want to say the switch will be near the passenger side inner fender, but I'm not positive about that... On my '91 it was on the CAD on the axle itself which I understand is atypical. If your 4x4 light is on, but otherwise the 4x4 is engaging and disengaging normally, there's a chance the light's switch is stuck. But the light itself receives constant power with the switch connecting it to ground, so if the wires are shorting to ground before the switch, the light will stay on as well. Should be easy enough to tell which one the problem is, if you locate and unplug the switch and the light goes out, well the problem is either with the switch it the switch's ground. If the light stays on, you've got a short somewhere. Good luck! Also I have to laugh at Calgary being cold. It was -37°C here this morning, not counting the windchill. Not to one-up you or anything... Link to comment Share on other sites More sharing options...
desbennett004 Posted December 17, 2016 Share Posted December 17, 2016 ^^^^ Haha, I haven't been that cold for a while, was only -22 here this morning. Sent from my SM-N900W8 using Tapatalk Link to comment Share on other sites More sharing options...
gogmorgo Posted December 17, 2016 Share Posted December 17, 2016 It's been getting up to around that during the day for the last week, but the windchill stays down in the 30's and 40's. It's deceptively nice-looking out too because it's so clear and sunny. Link to comment Share on other sites More sharing options...
Tex06 Posted December 18, 2016 Share Posted December 18, 2016 Not sure what you mean by On Demand, but I think you're referring to the full-time 4x4 of the optional 242 transfer case, which isn't an automatically engaging 4x4 like the cheap GM (and probably others) setup, it's an actual full-time 4x4 with a differential in the middle. I'm pretty confident it wasn't an option on any year MJ but I could be wrong. At any rate, no, the CAD (central axle disconnect) is a vacuum-engaged unit that connects and disconnects the two pieces of the front passenger axle shaft, which prevents the driveshaft from turning in 2wd, saving you an infinitesimal amount of fuel but mostly meaning kf you don't use 4x4 very often, it won't work the next time you try. Compare the front passenger side axle tubes on either Jeep. The XJ will be straight and simple, the MJ will have a bulge with some vacuum lines and maybe wires going to it. If your 4x4 works, great. If not, that's likely your problem. You can look into permanently locking the CAD, which is super easy and won't cause any problems down the road that you wouldn't have anyway, and you likely won't notice much if any hit on your mpg. As to the light, it's switched by a vacuum switch, which is driven by the same lines as the CAD, (which come off the Tcase, near the speedometer assembly in the tail housing). I want to say the switch will be near the passenger side inner fender, but I'm not positive about that... On my '91 it was on the CAD on the axle itself which I understand is atypical. If your 4x4 light is on, but otherwise the 4x4 is engaging and disengaging normally, there's a chance the light's switch is stuck. But the light itself receives constant power with the switch connecting it to ground, so if the wires are shorting to ground before the switch, the light will stay on as well. Should be easy enough to tell which one the problem is, if you locate and unplug the switch and the light goes out, well the problem is either with the switch it the switch's ground. If the light stays on, you've got a short somewhere. Good luck! Also I have to laugh at Calgary being cold. It was -37°C here this morning, not counting the windchill. Not to one-up you or anything... Great freaking writeup! I've been trying to get my light to.....well, light. Sent from my SM-G930T using Tapatalk Link to comment Share on other sites More sharing options...
Alanmizzen Posted December 18, 2016 Author Share Posted December 18, 2016 Oh man! Ya I'm not complaining about the cold. Cause compared to -37 well, ya. Snow this long in Vancouver is quite rare. But it's been fun. I love how well my 88 does in the snow. Thanks for all the replies I'll be doing more investigating this weekend. So I'm out of 4hi but the light is on. As for now we have our annual Christmas house party tonight I'll post more here when I dig some more. Link to comment Share on other sites More sharing options...
gogmorgo Posted December 18, 2016 Share Posted December 18, 2016 No worries guys, I'm happy to help. I can't say I remember every detail because it's been 16 months since I was going through this, but everything I learned was trying to make my full-time light come on after swapping in the 242 in place of the 231. Turns out everything was working except that my cluster didn't have the circuits for the full-time light. Maybe eventually I'll swap in the proper cluster I've got sitting in the basement, but that time is not this time. As far as running in 4hi, you'll likely be gone on any surface other than dry pavement. Most of my mom's family lives in the Lower Mainland or on the Island, and you guys got a $#!& ton of snow, at least for the Lower Mainland. I grew up on the Island myself, and I'm not convinced there's such a thing as dry pavement out there this time of year. Rainy (or sometimes snowy) season for sure. Although to be honest, even out here where I won't be able to see the street I live on until March or April because of the snow, before I swapped in the 242 Tcase, I prefered driving in 2wd because I couldn't stand the understeer in 4hi... But to each their own. Since swapping in the 242 I'm in full-time 4x4 most of the time in the winter unless I'm on the highway, even when pushing through snow well over a foot deep, until I start struggling at least. It's definitely an upgrade worth doing if you ever end up driving on slick roads. I even use it on gravel in the summer — I can take corners 5-10% faster in full-time than in 2wd or 4hi. Twice the traction but almost invisible, especially with CV axle shafts. Link to comment Share on other sites More sharing options...
Alanmizzen Posted December 21, 2016 Author Share Posted December 21, 2016 Well the light went off on its own. I'm guessing something with the cold that wasn't allowing it to switch off. Weird Link to comment Share on other sites More sharing options...
Alanmizzen Posted December 21, 2016 Author Share Posted December 21, 2016 Thanks for all the help guys! Link to comment Share on other sites More sharing options...
gogmorgo Posted December 22, 2016 Share Posted December 22, 2016 Yeah, could have been a bit of moisture stuck the switch open, although that could indicate a vacuum leak. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now