How to: Deleting ADD system

I’m not a mechanic but I’m trying to learn so excuse my ignorance please. So after the swap is complete the front drive shaft always is engaged. So when you swap from 2hi to 4hi is the transfer case what controls power being sent to the front?

 

No. The front half shafts or CVs are locked to the wheels and spin from the splines inside the hub. They turn the spider gears inside the differential spinning the front driveshaft that is “unlocked” in your transfer case in 2WD. When you shift into 4HI or 4LO, you lock in the front driveshaft shaft to the transfer case and start pushing power the opposite direction. Engine crank turns, turns torque converter or clutch, then transfer case primary sends power to front and rear driveshaft. Front differential sends set power to the front wheels inversely proportional to their traction through the CV shafts. If one wheel spins, then it receives more power than the one not spinning. Make sense? This is how an open differential works. Locking differential send equal power to both wheels regardless of traction. You probably have the stock open differential.

 

What you said and what he said are the same thing....transfer case drives the front once in 4H.

This is actually not correct. An open differential always sends 50/50 torque to both wheels. The one that spins requires a certain amount of torque to spin...the other wheel is receiving the exact same amount of torque as the spinning wheel, but that is not enough torque to drive the vehicle, so you just sit there and spin the one with the least amount of traction. A locker guarantees the wheels receive equal speeds, but all the torque could potentially go to one wheel, aka the wheel with traction.

 

You said it much better than I. What I wanted to stress that would be different is the ADD system prevents the front drive shaft from turning all the time. If he switches to a manual diff tube it will spin full time.

 

Thanks for the help guys! Recon I might as well get a locking differential when I do this? If so, any recommendations?

 

Opening a new can of worms there. If you're adding in a front diff lock, do you want to regear?

 

Totally separate mod. You don't need to crack open the diff for the FJ tube swap, so not really a justification for doing a locker while you're at it.

 

Well I’m having issues with my front gear coupler where the front actuator connects stuck in the 4WD position. I haven’t drained the front diff yet due to a stripped out drain plug (thank you previous owner). But I’m assuming there is going to be some metal shavings on the plug. I was looking into replacing front diff anyway. Factory gears can clean out my 285/75 no problem. I don’t plan on regearing yet but possibly one day. I still daily this rig so fuel economy is chirping in the back of my mind. Demon on my shoulder is saying to regear while I’m doing all this.

 

the stub shaft gets replaced with the FJ full time tube so if that part of your truck is damaged it will go away with this mod. No need to do anything to the differential itself.

 

So has anyone made a kit to use a cable to move the transfer case in and out of 4wd. Seems like they would sell like hot cakes. Especially as all these Toyotas get old and these actuators take a shit and you can’t find new ones.

 

honestly it’s cleaner to just put a manual case out of an FJ in. You will need to install a shifter mechanism for cable operated one into the cab anyway so might as well put an OEM part in that’s known to be super reliable.

 

Treehouse Offroad tried on his Sequoia, on YouTube, but it didnt work. Like @6 gearT444E said, replace it with a proven Toyota part, and eliminate the actuator that fails

 

Link to the video? My searches were unfruitful; although I now know more than I ever wanted to about suspending treehouses with cables...

 

He mentioned it around 18:20

https://youtu.be/1-pLyGRmtnc?si=IPvS3h3T-9sO9oDj

 

Ahh, ok that explains it, was looking for a video specific to that effort. Thanks!

 

They say the definition of insanity is doing something over and over again and expecting different results. Thankfully, this time when I swapped the ADD, I was not a victim of insanity. I am back on stock 4.30 gears in the 3rd gen and so my driveshaft speeds are slower. I took it up to 95 with no issues.

Also, I wonder if part of it is that the diff I have now is out of a TRD pro which has spider gears that fit the carrier perfectly instead of being located by the CV and intermediate shaft. I feel like maybe with a more precise diff, there’s less chance of stuff moving around and causing vibes. I’m curious now if the vibes would come back or not if I regeared again.

Anyways, I’m glad to have that done and now I hope to do a manual t-case eventually.

 

You sticking with the 3G then??

For your FJ swap notes, I have no vibes with my AWD case and the associated shorter rear/longer front shaft, and a few flavors of suspension setups (largest one being the '23 Pro that I am on, which is in the 2-2.5" lift territory on my 2G). It briefly had a slight "growl" that started at about 50-55 MPH and made my loose rear view mirror vibrate a little, but it just kinda went away over a couple hundred miles; maybe the new U-joints getting settled in or something, not sure..

 

Man, I don’t know. Leaning more and more towards it now that my previously thought to be issues don’t actually exist (AC and trans leak). I like that I’m nearing the end of truck payments and I don’t like that a 4G sets me back again. No matter how much equity you have, they tend to always find a way to make it feel like you’re starting from the beginning again. I like that the 4.30s and transmission combo achieves record mpg for me, without feeling too shabby on acceleration down low like stock did. I still completely despise what this engine is, but I can live with it like I have for 75K already.

The other part of me thinks a 4G would be absolutely awesome for a number of reasons. In all reality, it’s the truck I’ve always wanted that no one would build. Power/torque, manual, modern features. Priority is buying a house, so kinda shying away from money on truck stuff for now and working on that. I’m thinking I add a 4G to the fleet in a few years and keep the 3G just because it won’t be worth the lousy trade in, and I can burn miles on it or use it on the risky weather days. Lots of hail here.

As for vibes and ADD related stuff, I seemed to get them right around 85 mph on the 5.29s, but it kind of felt like they were slightly starting at around 75-80. Nothing major, just a very slight rumble. 85 mph was something like 4600 driveshaft rpm, so that’s pretty fast. Either the 4.30s lowered it enough that even 95 mph is in the safe zone, or this TRD Pro diff with the better spiders nixed it. I’m thinking that it was the regear that caused this before.

No lift on my truck, but even if I did have lift it wouldn’t really do anything for the ADD and front diff, since that relationship doesn’t change without a diff drop. I’ve never had a single rear vibe on the stock setup (not even 100 mph on the 5.29s)….so I am happy with that.

 

I've never heard of the diff gears being different in the Pro diff. I learned something new today

 

It’s actually pretty interesting and I have a lot more info I could share, I’ve thought about making a thread to outline the differences. I don’t have 100% proof, but I know they are different in the Pro and Trail Special Edition vs the other trims. The entire diff assembly is different and then when you dig down into all the separate parts, the only different parts are the spider gear kits and the carriers.

I have seen shops say that “newer” Tacoma’s have perfectly fitting spider gears. I think that is incorrectly attributed and that what probably happened is the shop saying that worked on a Pro instead of another trim. The truck they were working on was likely new at the time and thus they probably made the assumption that newer trucks finally had spider gears that don’t move relative to their bore, when in reality, they simply were working on a Pro.

As we all know, Toyota installs the bearing for the CV, because the CV is spinning at vehicle speed while the diff sits still. So the CV needs to rotate relative to the diff, and the bearing helps with that. But ECGS has demonstrated that the side gears do not fit their bores properly. So you can surmise that the CV located by the bearing is actually holding the side gear in the correct location too.

Then you think about a Trail SE or Pro, and consider the fact they have factory lift in the neighborhood of 2”. Toyota still installs the bearing which supports the CV, but then if they actually fix the spider gear bore, then now you have the bearing AND the side gear holding the CV straight, so no vibes with lift, and no vibes caused by the spider gear being out of alignment or a tweak on the CV due to the lift angle since the spider gear keeps the CV tip in the right spot.

Another supporting factor is that they actually had a TSB for trucks getting vibrations that go away in 4wd…I forget if the TSB was for all trucks or for just ones that had the TRD lift installed, but regardless, the fix was to install the applicable TRD Pro diff in any non TRD Pro model that had vibes. So that furthers the idea that the TRD Pro/Trail diff spider gears actually a problem solver part and help support the CV vs gears being loose like the other trims.

All of those factors are why I say the carrier and gears are different. It just makes too much sense to be anything else. The real question is…why TF doesn’t Toyota just use the proper fitting gears and carrier on all trucks? I mean seriously??

Essentially, we can draw from this that the bushing from ECGS is actually a band aid fix, but it’s a bandaid that happens to work and work well for what we are doing with it.