kyle, i could be wrong, but i don't think my hubs are vaccuum operated. however i will say im not exactly sure how they do work.

 

did you have ADD? i'm pretty sure the axle itself has a vacuum disconnect, meaning that vacuum makes a collar slide off one of the axle shafts when not in 4wd, keeping the rest of hte front from spinning.

auto hubs were the same size as a manual hub, but didn't have a dial and said AUTO on them

 

Thats exactly right, a collar makes the carriers sleeve slide off the stub axle on the drivers side. Thats the ADD system. Non ADD systems have a stub axle too, but it just plugs directly in to the main part of the diff, not an adapter with the ADD inner workings. And the AUTO unlocking hubs were availiable until 1988, and in 1989 the Auto Disconecting Diff replaced the hubs, and the hubs got a plate to lock the hub to the spindle constantly. You cant back up and unlock the CV axle from the spindle on 89+ vehicles with ADD. YOu can on 88 and earlier AUTO hub vehicles....

Just remember this, there is a difference between Auto Disconnecting Diff, and Auto locking Hubs.

 

That's what I have. I really like it because it has the V6, 4WD and 5 speed, but none of the luxury crap that adds weight and has potential to break. I could always add a locker later, but at the moment I don't wheel enough to justify it....

Ian, look at your front wheels. If they have a little dial in the middle with marks that say 'free' and 'locked' then you do have manual hubs. And that means you have to get out of the truck to engage 4WD - regardless of what the indicator light on the dash says. HTH

 

I knew fromthe get go I didn't have manual hubs, what I've come to understand, thanks to this thread, is that my taco as the auto disconnecting differential (the ADD). My other questions still stands (I think), If I go for a juicy lift in the future, will I want/need to install maual hubs?

 

Back when I shot the news, our station had a bunch of blazers, which I now see had the auto hubs-had to do the backup deal-sucked IMHO.
Actually we had a couple newer blazers which must had had ADD, as all you had to do was hit a swithch on the dash. Why blazers you ask? because Dayton ohio was/is a GM town, and they made them there. Make the trailblazer there now (just a little trivia on the side for those who dig that sort of stuff).

 

ADD is a toyota thing. not sure what GM used. what years were they? old straight axle blazers could be had with auto hubs, but all S10 blazers and IFS blazers came with some kind of vacuum disconnect

 

We swapped the (add) hubs off my buddys 86 runner... total junk. All that was left inside the hubs was powder. Manual hubs are the most reliable IMO, albeit I have to get off my lazy ass and engage them outside the truck. My 97 has auto hubs and they are ok, so long as the thing remains stock.

If you do a lift in the future then yes you'll prefer manual hubs as opposed to auto's. Reason being that the auto's are not meant to handle the new cv stress your gonna be putting on them with a lift.

 

The 86 had the auto's and ur 97 has the add, or atleast i think so.

 

http://www.off-road.com/toyota/tech/aisin/

 

I 'm guessing I have ADD on my 1993 4Runner. I'd like to put a set of Warn hubs on. From what I am reading, manual are the way to go. When I bolt up anew set of Warn's, do I have to disengage anything from the ADD system like vacuum lines? Some delaers tell me I need a conversion kit but Downey offroad says thats not necessary. Any feedback would be appreciated. If you can, please copy and paste your response to my mailbox. Sometimes I have a hard time finding these threads. THANKS!!!

 

I am trying to understand how my diff works when I put my 4runner in 4 wheel? Ive got a 5speed 98 4runner and im pretty sure it has the ADDs. Now dose that mean that no madder what the diffs will always be locked when I shift to 4wheel? I have noticed that when i switch to 4high the front diff seems to lock up. When i take sharp corners i can feel the wheels slip. Is this suppose to be happening? Dose the ADD mean the front end will always be locked in 4wheel?

 

The front diff doesn't "lock up" it merely engages 4 wheel drive. This means the sliding collar moves over, and engages the diff/driveline to the front axles. The front axles are already engaged to the spindle/hub assys, so no need to get out and lock them in place in an ADD system.

The reason the front end feels "locked: is because you are trying to turn with the truck in 4x4. On pavement, the front wheels will want to try and follow the same path because its in 4x4, despite the fact that the outer wheel will turn faster than the inner. Trucks with open center diffs (IE the transfer case) do not experience this problem, but they are not very good for offroading until the t-case center diff is locked in.

 

I appreciate your help in trying to teach us not so mechanical people how these things work. I just want to make sure that I’ve got this right. So on my 4runner there is no differential between the front and the back or between the two front wheels. Therefore this should only be used in snow or off road conditions otherwise it would cause extensive wear. How would I know if I had and open center diff so that I could drive in what I call “all time, All Wheel Drive”? Also, Those trucks with the “RR Diff Lock” button would have the option of locking up the rear end diff as well as the already locked front wheels in 4 wheel drive?