Hi All,
I'm new here so hoping my questions are not too dumb.
I just picked up a new to me 96 t100 4x4. (3.4l & auto trans)

The truck has a few problems, one being it will not engage into 4x4.

After a lot of research here, it seems most likely to be the actuator, ADD relay or ADD switch.

After even more research I came across this article to completely bypass the ADD (Automatic Differential Disconnect) system.
http://www.4x4wire.com/toyota/tech/add/

It seems just a little "too good to be true".

Has anyone here actually done this?
I guess my main questions are
1. does it work as it should?
2. Do the dash lights still show "4x4 on"?
3. Any real downside?

Thanks in advance,
K

 

good question, i hope someone can chime in

 

I just wanted to follow on this post to possibly help others.

Here are a couple of replies from another forum.

#1

" I actually just pulled my front diff out and removed the actuator to prep it for shipping this morning. And yes, it looks that easy. Actuator is on the passenger side, 4 bolts and its out, you can engage 4wd by sliding the collar over. As the collar moves over it presses an indicator switch which turns your 4wd light on. I nearly did this mod when my actuator would not operate in cold weather.

And as Aikane said, if you get an electric actuator out of a newer tacoma/4runner it will bolt right in. Wiring it on the other hand will be another bag of fun."



#2
Yes it works, though later models use an electric motor instead of vacuum to move the shift fork.

#3
The 4X4Wire information is spot on! I just did the mod on my '90 4Runner (with changing out to manual hubs as well) and it works great. I was concerned that the 4x4 light would burn continuously, but it only comes on when the transfer case is shifted into 4x4.

 

well since the 4wd light is in the T-case ( i believe) then it wont matter.

yes it works as it should, thousands of people have done this over the year, never heard of any problems.



you can also TRULY defeat the ENTIRE ADD system by replacing the ADD tube on the dirver side of the differential with a NON-ADD tube.
However i'm not sure if this is possible on your T-100, although it is true for 3rd gen trucks and 2nd gen 4runners.

 

Works perfectly and it is completely defeated without swapping the tube. I didn't swap out the ADD tube, but they are the same as the old pickups. The CV joint is longer, so it is fine if you want to go to the trouble. The tube swap does get rid of one slip connection that could fail, but it has nothing to do with the system after its locked out.

The main reason I wanted a T100 over a Tundra is because of this easy ability to switch out the hubs and go manual. .

I think the the 4WD works better manually than with the ADD system. You can shift from 4WD High to 2WD and back any at any speed, whenever you want as long as the hubs are locked. Try this in a Tundra! HA!

With the ADD system you are limited speed wise and disengaging is a lot harder...you have to stop, basically. In the summer disengage the hubs and save wear and tear, in winter you can leave the hubs on and drive in 2WD as much as you like.

 

Just a thought... Is the 4x4 light in the dash coming on when engaged? My 4Runner didnt have 4x4 when I bought it and the light didnt come on in the dash. Ended up being a split wire on the top of the t-case so the ADD vacuum wouldnt work. Connected the wire and BINGO, easy fix!, dash light came on and vacuum engaged 4x4.
Good luck.

 

+1 on the manual hub switch. I was having problems getting in and out of 4wd until I swapped out the hubs.

 

Hi all,
Just an update. I did the manual hub conversion and also removed the ADD.

It was a very easy job. The hub swap was one of the better upgrades I made to my truck.
I keep a pretty good eye on the MPG and it seems I pick up 2 MPG. For me this was completely worth the swap.

Thanks again for all the help.
K.

 

Before you go through all of that trouble, check the vacuum line to the differential for air leaks. I had the same problem two years ago, and fixed it with $5 worth of vacuum hose. I'm totally for getting rid of the system, but if it works for now, why not?

 

sorry for bringing it back to life, but if you delete the ADD system its bulletproof then! you spent $5 on vacuum hose when i spent 5 min slipping the yoke over and take a small piece of vacuum hose and connect the inlet and outlet together on the diaphragm.

 

What is Toyotas reason for the ADD, if it works better deleted?

 

Convenience. You don't have to get out and lock your hubs with ADD. It does cause a lot of unnecessary cv wear, but it keeps the front driveshaft from spinning when your in 2wd. ADD also works better than the auto hubs they used for a while which tended to unlock in reverse.

When I do convert my truck to manual hubs, I'll leave the ADD as it is. I plan on leaving the ADD intact though, as I'll just leave the hubs locked all winter and there's no sense in getting the front drive shaft spinning if the transfer case isn't engaged.

 

Oh, so if you delete ADD you have to go to manual hubs or the drive shaft will spin?

 

Yep, all the time. And like I was saying, up here you want your hubs locked all winter, and if you delete ADD, your diff will spin the driveshaft when they're locked (which probably won't hurt anything but the fuel economy). It's one thing for guys down south to lock them when they go to a trail and unlock them when they're done. It's quite another for us to get out every time we turn on/off the highway. So, if your ADD is working, I wouldn't advise disabling it - at least if you live in area where crossing a barbed wire fence on a snowmobile means riding right over it.

 

A mod that is relevant to this that I have been thinking of doing (until I post here and hear why I am wrong for thinking this will work)... If you have a older 4runner that came with manual hubs and a tcase that you need to shift into 4wd (89' in my case), could I keep my manual hubs, install a locker in front diff (I am thinking spartan), and install ADD tube and actuator and use to engage locker. What I am thinking is with tcase shifted into 4wd, hubs locked in, and ADD disengaged the power will go to front passenger tire. Engaging ADD would essentially lock front end and distribute power to both. Am I nuts or do I have something?

 

Sorry to revive a old thread. I have a 1993 automatic 3.0 4Runner with the add system. If I lock the actuator in the front diff will this cause any excessive heat or lack of fluids moving around in my transfer case or transmission? Or does this mod work for both manual and automatic transmissions? I bypassed the vacuums last year to force my actuator over to 4wd but my trans temp got hot really fast and I was unsure if it was related to me forcing it to 4x4 or not.

 

I have a different issue question. Does anyone know what voltage the vacuum actuators switches run on? I would like to be able to turn them on manually because I have put a TWD body on a 4x4 chassis and the wiring harness is from the TWD because the original 4x4 harness was chopped up.so there's no connection to the T-case. I'm wanting to keep my ADD system but engage it manually and add manual lock outs????

 

Should be full charging voltage. 12 volts nominal. Actual voltage with engine running, more like 14.5 volts.

Can't you measure the voltage supplied to the VSV when 4WD is selected??

 

The problem I have is that I had to use a TWD wiring harness, due to the fact that someone cut the fwd factory harness. The power to those switches on the transfer case are not connected to activate the power to the vacuum supply valves. I'm wanting to wire the T-case switches manually to have them activate the VSV for the ADD. I'm only wanting to know what the voltage is in the operation of this system, and what ohm values may be needed for it to operate safely and correctly.