Need info on adding front ADD axle, wires, switches, to non ADD truck

What diff/axle should I put in my IFS front end, ADD or non-ADD

  • Put in ADD axle/diff and fab/hook up the ADD switches (manual hubs and push button 4x4)

    Votes: 1 20.0%
  • Put in ADD diff with non-ADD axle (manual hubs only)

    Votes: 0 0.0%
  • Keep entire non-ADD diff/axle and jut put in 4.88 gears (manual hubs only)

    Votes: 4 80.0%

  • Total voters

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Feb 6, 2006
Anchorage Alaska
First let me say I did a little searching but did not find anything on this kind of mod. If it has been covered forgive me and please give me the links. Thanks.

ADD = (Automatic Differential Disconnect) or push button 4wd.

My truck is a 1992 non ADD (manual hubs) 22re manual.

I just picked up a ADD front diff and axle assembley from the junkyard because it had the 4.88 gears in it and I am doing a mild lift to fit 33's and regearing.

I have done some research and found that the ADD set up is a little better because of some needle bearings that hold the axle instead of the brass bushings.

I also found that you can switch out the long side axle tube and axle with the non ADD unit so I know I can go this route.

I have been toying around with the idea of leaving the ADD switch in the axle tube and wireing my truck for the ADD so I could have manual hubs and push button 4wd if I chose. Might be handy for winter driving.

  1. So has anyone done this?
  2. Know of any info, parts, etc. I may need?
  3. Is the ADD a weak link in the axle?
  4. And is it worth the work or should I just stay 100% manual
Last edited:
First off, I mean no offense. But is it really a big deal to get out and lock your hubs? Adding extraneousness parts to the front end just so you don't need to get out and lock your hubs doesn't make sense.

But to each their own.
No offence taken, I have always prefered manual hubs. It was just a thought I had since I already had all the parts. I bought the whole third member/axle for less than the price of new gears. So I figured I would save $ going this rout, plus they are already installed, and broken in.

I will likley Keep the ADD diff and put the non ADD axle and housing on the long side so esentually it will be a non ADD axle with the bonus of having the needle bearings instead of the bushings. I think this is the best and easiest way to go but if I am wrong someone please let me know.

I was curious if anyone had done this mod or what opinions are on adding the ADD switches/vacume etc. You are probably right, more hastle and $ than it is worh but thought I would ask.
For enabling the ADD, you will need a vacuum switch and line to a vacuum source. Either manual or electronic switch will do. If you use and electronic one, a switch to activate it will be needed. If you go the electronic route, it is possible to use the 4WD switch in the transfer case to switch the vacuum switch. I suggest taking a look at the diagrams in the FSM for how to do it.

For the 4WD indicator light, there is a switch in the ADD front axle that indicates when it is engaged.

As for being push button 4WD, more like lever action. I have a '95 with ADD and manual transmission. Moving the transfer case shift lever into 4WD is what actuates the ADD system.
Convert the 3rd to non ADD much less issues, there is a reason many guys want to swap to the locking hubs.
I keep my hubs locked 5 months out of the year during winter. Even on the days without snow I can hit 4wd on icy patches.

Just bypass the 4:88 ADD, you should be fine without retrofitting the system.
I'm prolly missing something and gonna sound like a complete idiot here... but isn't the ADD in the axle housing? I mean, your goal here is to get the cheap 4.88 gears... so couldn't you swap out the thirds. That would get your 4.88s, and keep the solid (non ADD) axle housing... Right?

I have a 3rd Gen 4runner. I put in manual hubs to save my CVs with my lift... and everyone told me, when I eventually swap gears, to get a solid (non ADD) axle housing cuz the ADD is a weak link.

And yes, I am on my 2nd rum and coke... so I am aware that I just have to be missing something here. Check out the no-typos... nice!
FYI I have been running a 4.56 ADD front axle that I simply installed and used a vacuum pump to lock it into the locked position for 2+ years now, and it's been fine... I did not hook up any vacuum lines or switches, and I have done nothing in the way of maintenance, it just keeps working fine... I already had manual locking hubs...

Users who are viewing this thread

Top Bottom