is it possible for the a4wd to engage without the light coming on on the cluster ?? ive been noticing a humming sound when going above like 15mph from up front and around 55mph i start feeling a vibration, nothing horrible but noticeable and it just feels like the 4wd is engaged?? but my switch is off and the lights arent on indicating its in 4wd

 

could be a vac malfunction... and switched off and staying on....

 

If you turn the switch to A4WD does the light come on, how about the 4WDH position and does it get a different feel to it, like tires skidding in the sand when cornering?

 

yeah when i turn the switch the lites come on. the sound is very similiar to what a large mud tire 35"+ would sound like humming down the road, but i really only hear it from inside the cab, if i roll the windows down i dont hear it?? i also hear it on de acceleration too. ill trey switching in the other 4wd modes to see if theres a diff but as of rite now it doesnt make any noises or feel any diff driving on the street??

 

Hello, I think I had the same problem with my 1999 expy xlt. When I installed a new battery, I tried to drive and it felt like it was in 4wd, but no light on dash. I turned 4wd swith and got no response. I had to put the truck in netual and then turn switch. This time I heard it go in and out of 4wd. This fixed the problem for me. So I guess it is possible to be in 4wd with no light on the dash.
Good Luck with your fix

 

If your shift motor went bad the last time it was in 4WD, then it could be stuck in 4WD even though the switch is off. That's why I was asking if it felt any different when you did switch it into 4WD. Since there is no difference, then it's in 4WD all the time.

 

well im gonna try it in reg 4wd and 4L, i did switch it in a4wd like a week or so ago when i was messing with the stereo cause i had to unplug the switch. if the motor went bad is there anyway to take it out of 4wd as a temp fix?
update:
i just went out and switched from 2wd to a4wd, no diff that i can feel cruising around the neighborhood. from a4wd to 4wd again not much of a diff if any, 4wd to low and theres a diff, i can hear it engaging when i switch beetween 4wd and 4L cant hear anything really from 2wd to a4wd? AWD wouldnt feel to far off from 2wd though would it?

 

also since ive upgraded my tires and now have 305/45/22 wheels would this effect the A4WD? in some of the searching ive done ive read were diff wheel sizes and all can make the A4WD act up?? can the A4WD come on without engaging it if it notices a problem?

 

If you are stuck in 4wd drive you would know it when you turn in a parking lot because you would be binding up. I think the AWD detects wheel slip by comparing sensor / rpm info from each wheel. Even with bigger tires / rims the wheels should all be going the same speed especially when driving straight down the road. Just my thoughts.

 

whats the diff from A4WD to just 4WD? cause im thinking its having a problem with the A4WD, wouldnt that handle diff when cornering and all then when in 4wd?

 

In 2WD the front driveshaft and axle are disengaged. With A4WD the front driveshaft is engaged but the front axle is not. If rear wheel spin is detected, the front axle is engaged and you now have temporary 4WD. After a period of time, the front axle is disengaged once again but the front driveshaft remains engaged. In straight 4WD (hi or low) both the front driveshaft and axle are engaged full time.

 

I was commenting on "locked in 4wd". Locked in A4WD shouldn't have any effect on normal driving if there is no relative wheel slip. I keep my Expy's in A4WD all the time. For what it is worth when A4WD hooks up it isn't smooth - it is a pretty rough engagement, so to think it is happening at 15mph and above I'd have to guess that isn't the issue.

 

well at 15mph im meaning im starting to hear the humming sound from the front, it gradually gets louder the faster i go but even at 55mph is still not very noticeable but there. switching from 2wd to a4wd it doesnt make any sound hardly, what sound it does make sounds like it comes from the dash or something .from a4wd to 4wd it makes a noticeable sound and the same from 4wd to 4L. but in a4wd do you get a vibration at HWY speeds? ive played around with the switch going back and forth with it through the diff settings and it still is acting the same with the humming sound and vibration above 55. im gonna try disconnecting the battery next and see if that makes a diff. this is all assuming this is my problem too? i do know when i switch to 4wd and 4L i can go around a corner without any tq bind, and i know for a fact 4L is working . possibly the larger 22' street tires dont get the same feeling as a offroad tire on the street?? is there a fuse that can shut off the a4wd?? i see in my manual the fuse for the 4wd transaxle and pulling that makes no diff, but not sure if that would be the rite fuse though??

 

No noise from A4WD at highway speeds. If you turn a tight circle in a dry parking lot in 4WD it should bind if 4WD is working. It pretty much has to by definition, regardless of tires. The binding is caused by the differing speeds of the two tires and no way for the drive line to compensate for it.

 

Pulling the fuse won't help. The shift motor needs power to both engage and disengage. Without power, there is no chance for the shift motor to pull it out of 4WD. If the problem is truly a bad shift motor as I suspect, then all you can do is replace it. Just in case this is a control circuit issue, you can try disconnecting the battery for 10 minutes to reboot the computer and see if that helps.