Hello,
I recently acquired a new (to me) 1991 4Runner that has the A.D.D system for disconnecting and connecting the 4WD.
The problem:
While driving with the transfer case in 2H, the front axle makes this horrible grating/humming noise and vibration (its so bad it vibrates my knuckles while holding the steering wheel) but it instantly goes away when it is put into 4H or 4L.
What i have done so far:
I looked around on here and found some useful articles on the ADD system and its function. What I did was put the drivers side tube for the front diff actuator directly connected to a strong vacuum source with a check valve and connected the vacuum resevoir to the disconnected VSV (the red one) so there would not be a leak, this cured the problem of the noise and vibration from the front axle while in 2H.....only for a few hours.....now it does it intermittently and even worse than before (sometimes even for just a second) I think that the actuator on the front diff is bad seeing as i checked almost every vacuum hose i could see and none were broken (yes even the ones to the actuator) or that the previous owner drove it like this while it made this horrible noise for so long (he was a super space cadet, no understanding of mechanical anything, could probably burn a pot of water if he tried) that the locking mechanism is just FUBAR inside there, but i drained the fluid from it and it was a little dark, but no abnormal amount of metal shavings were suspended in it (?) and it did not smell funky or burnt.
Any ideas/suggestion/theories would be appreciated since I know nothing about japanese auto makers and their love of vacuum controlled systems (i am an old school BMW Audi Volkswagen guy)
Jon H.
HAPPY HOLIDAYS!
oh and it has the 3.0 3VZ-E, if that helps
I recently acquired a new (to me) 1991 4Runner that has the A.D.D system for disconnecting and connecting the 4WD.
The problem:
While driving with the transfer case in 2H, the front axle makes this horrible grating/humming noise and vibration (its so bad it vibrates my knuckles while holding the steering wheel) but it instantly goes away when it is put into 4H or 4L.
What i have done so far:
I looked around on here and found some useful articles on the ADD system and its function. What I did was put the drivers side tube for the front diff actuator directly connected to a strong vacuum source with a check valve and connected the vacuum resevoir to the disconnected VSV (the red one) so there would not be a leak, this cured the problem of the noise and vibration from the front axle while in 2H.....only for a few hours.....now it does it intermittently and even worse than before (sometimes even for just a second) I think that the actuator on the front diff is bad seeing as i checked almost every vacuum hose i could see and none were broken (yes even the ones to the actuator) or that the previous owner drove it like this while it made this horrible noise for so long (he was a super space cadet, no understanding of mechanical anything, could probably burn a pot of water if he tried) that the locking mechanism is just FUBAR inside there, but i drained the fluid from it and it was a little dark, but no abnormal amount of metal shavings were suspended in it (?) and it did not smell funky or burnt.
Any ideas/suggestion/theories would be appreciated since I know nothing about japanese auto makers and their love of vacuum controlled systems (i am an old school BMW Audi Volkswagen guy)
Jon H.
HAPPY HOLIDAYS!
oh and it has the 3.0 3VZ-E, if that helps
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