Question about Automatic Differential Disconnect (ADD) pre 2001

I did do a bunch of searching, but could not find a clear answer to this question.

I read on the wiki that only 2001+ tacomas had Automatic Differential Disconnect standard. So, how do you know if a pre 2001 has this? I also may not fully understand the feature. Does this take the place of manual hubs, where you have to get out and turn the things? Is the way to tell by looking at the caps on the wheels?

I do NOT want to have to do that each time I pop in and out of 4WD.

I would ideally love the manual shifter to move from 2WD/4WD/4LO, rather than an eletronic button, but again, without the need to turn manual hubs. Some older (1998-2001) tacomas seem to have a push button for 4WD while some have the manual lever. Anyway, that's not my main concern/question... I'm really asking about this ADD and what it is and what trucks it's on and not on.

Thanks!

 

But I'm trying to research buying a used Tacoma and I don't see an easy way of telling via online ads which ones have ADD, if they are pre 2001. Are there any other ways (i.e. V6, TRD, etc etc)? None of the ads seem to reference manual hubs. Was ADD a stand alone option pre 2001?

 

I am pretty sure that on '98 and newer models, ADD was standard. Though it may have been possible to special order a truck with manual locking hubs after that. You are much more likely to run into manual hub on '97s and older.

I'll bet EnolaGaia will come along shortly to set the record straight.

 

My 96 tacoma (3.4L Manual tranny) had ADD (Non- manual hubs).

It also had a gear shift for 4WD (not a button).

If the truck has manual hubs, it WILL NOT have ADD. If you look at the truck and you see this (or something similar)
Manual Hubs


With ADD- you will not have a dial on the front wheels.

Also...I think on the 1st gen trucks, the front axle shafts are a different color. The ADD had GREEN axle shafts. I think the non-ADD had BLUE shafts. Manual hubs should have blue shafts.

 

Great info, thanks. So, in short...it's as simple as looking at the hubs, as a final check.

 

Ezatnova, your last post is essentially correct. However, make sure that you pop the little hub caps off to check. Then you'll have access to the wheel studs and the ability to turn the manual locking hubs. I know it sounds dumb, but its just a simple reminder

 

Sorry for the stupid question, but, what happens on a manually locking wheel hub truck if you put it in 4WD abd don't lock the hubs on the front wheels?

 

Check this out: <http://www.oncourse4wd.com/4wd/4wd_free_wheeling_hubs.asp>

 

You won't be in 4WD

Putting it into 4WD at the shifter only engages the transfer case. If the hubs aren't locked on the front wheels, the axle shafts are turning & driving but that's it. That power isn't transferred into the wheels. No drive to the front wheels when the hubs are unlocked.

 

Ah got it. Thanks.

I guess I'll ace to be diligent about looking under the wheelcap cover things on any older Tacoma. That would not work well with me, to encounter the need for 4wd while trying to get to work, and having to stop and get out and mess with those hubs.

Still seems interesting to me that ADD was apparently an option box check item before 2001 (according to the wiki, at least).

 

You'll find that about half the people leave it in locked position full time anyway. People argue over whether or not it increases wear, or if you gain gas mileage, but I really feel its a moot point. Mine spend about half their time in locked, half their time in free. If I know I'm going to be using 4x4 at some point in time in the day, I just turn 'em to locked in the morning. Turn them back to free whenever I remember to. Your factory manual stipulates that you should drive with them locked 10 miles a month I believe to self-lubricate the parts.

Also, a lot of real off-roaders seem to prefer the manual locking hubs to ADD anyway. I believe its because manual is less likely to crap out on you or something along those lines -- maybe someone more informed can chime in. If you're not extreme about going off road I doubt you'll care one way or another.

Moral of this post is don't let ADD or manual hubs sway your decision one way or another very much. In the end, you have to "deal" with them so infrequently that its really not a big bargaining point.

 

Ah ok thanks. I was picturing having to turn / unturn these things concurrent with each switch to / from 4wd.

 

Just noticed you live in PA. When I lived in upstate New York (before I got my Tacoma), I had a lot friends who had trucks/jeeps with manual hubs. They all locked theirs at the first sign of snow. They said that if it got really cold, you could get ice on your hubs and it would be difficult to turn. They'd leave 'em on until spring, and never had any issues. Hope this helps answer your questions.

 

Excellent. Thanks.

 

Like anything else mechanical.... You'll wanna cycle that knob (engage/disengage) more than just a couple times a year.

I think the OP would rather have ADD anyway.

 

Definitely rather, but, at least I know it's not the end of the world if I find the "perfect" truck and it has manual hubs.

 

I prefer the ADD hubs - I don't actually buy the "less to go wrong with manual hubs" argument, at least, the difference has to be very minor if it exists. Manual hubs crap out all the time - plus around here they freeze up very easily. My truck has 200k on it, with ADD, and 4wd used regularly through its life (mountain truck), and it has never failed or experienced mechanical problems.

On the other hand, I've had the pleasurable experience of having to pee on a manual hub to warm it up enough to lock it.

Your choice.

-Sam

P.S. One thing I wish ADD didn't do - spin the axles while not in 4WD (extra CV wear when lifted..)

 

Yeah, I hear that - I have a mostly manual truck (transmission, windows, locks, etc.). The ADD is the one part that I'm glad is automatic though. I suppose the good thing is that Toyota does a pretty good job on both pieces of equipment, failures to either the ADD or manual hubs are quite rare, as far as I can tell.

-Sam

 

I have a question. I have a 2000 Tacoma with the 3.4 and the 4.10 dif. I found out fast that my current carrier is no good it pops an snaps when I engauge the front dif. I've replaced everything you would normally replace CV shafts,both sides, and have since replaced the locking hubs (mine came with manual locking hubs) with the good Warn hubs. I recently bought a front carrier out of a salvage yard. It has the ADD vaccum on it, my carrier doesn't have it on the dif. Now can I swap the difs an be ok? And also i took the vacume unit off and now mind you im still new to the Toyota 4x4 scene is the unit a limited slip?? or what because I can turn the yoke and it doesn't spin the passenger side splines.Also can I take my non ADD section off my dif and swap it on the ADD side?? Can you help clear this up because its driving me nuts. I'm a solider in Ft Benning Georgia an I need my 4x4. Any assistance or pointers will be helpful I'm a good mechanic I'm just a little lost when it comes to this section of the truck.